Mitigating identity attacks in DeFi through biometric-based Sybil resistance

Decentralized Finance (DeFi) has witnessed remarkable growth, providing innovative financial services in a decentralized and open manner. However, the inherent nature of DeFi platforms makes them vulnerable to identity attacks, such as Sybil ones, where malicious actors create multiple fake identities to manipulate the system. Sybil attacks can lead to financial losses, and fraudulent activities, and undermine the trustworthiness of DeFi platforms. Addressing this issue is crucial for the long-term success and sustainability of DeFi. This paper proposes a novel approach to enhance the security of DeFi platforms through the integration of Sybil-resistant techniques like biometric-based identity verification. The proposed integration offers a promising avenue for enhancing the trustworthiness and usability of DeFi platforms, ensuring a more resilient and secure DeFi ecosystem. “The human body is the best picture of the human soul.” – Ludwig Wittgenstein Introduction Decentralized Finance (DeFi) has emerged as a disruptive force in the financial industry, revolutionizing traditional financial systems by leveraging blockchain technology and smart contracts. DeFi platforms offer a wide range of financial services, including lending, borrowing, trading, and asset management, in a decentralized and permissionless manner. The open and borderless nature of DeFi has attracted significant attention from users, developers, and investors worldwide. However, this rapid growth has also brought forth various security challenges, particularly concerning identity attacks. One of the primary threats to the security and integrity of DeFi platforms is the Sybil attack when malicious actors create multiple fake identities or accounts to gain control over the system or manipulate its operation. By overwhelming the network with pseudonymous identities, Sybil attackers can execute various nefarious activities, such as double-spending, manipulating voting mechanisms, or creating artificial liquidity. These attacks not only compromise the trust and reliability of DeFi platforms but also pose significant financial risks to users and investors. Addressing the challenge of Sybil attacks in the context of DeFi requires robust and innovative security measures. Traditional solutions based on central authorities or reputation systems are often incompatible with the decentralized and trustless nature of DeFi. Therefore, alternative approaches that leverage biometric authentication and verification mechanisms and advanced cryptography have appeared. This promising avenue aims to enhance the security and resilience of DeFi platforms, bringing desired Sybil-resistant. This paper presents a comprehensive exploration of the DeFi phenomenon through the lenses of identity management. It proposes the integration of biometric-based identity verification to defend against identity attacks in DeFi. We delve into the intersection of DeFi, Sybil attacks, and biometrics. We start with an overview of DeFi’s key principles, and the advantages, challenges, and limitations of DeFi. Then, we aim to examine the challenges posed by Sybil attacks in DeFi systems, explore existing Sybil resistance approaches, and investigate the role of biometrics as a potential solution. While analyzing the strengths and limitations of biometrics, we aim to shed light on its potential applications and its ability to mitigate Sybil attacks in various aspects of DeFi, such as lending, asset management, decentralized exchanges, and more. Ultimately, this research seeks to contribute to the understanding of the importance of addressing security vulnerabilities in DeFi systems and highlight the potential of biometric-based Sybil resistance mechanisms in enhancing the trust, security, and integrity of decentralized financial platforms. By developing effective security measures, we can pave the way for the widespread adoption of DeFi and usher in a new era of financial inclusivity, transparency, and autonomy. Research problem The research problem at hand revolves around the issue of identity verification in decentralized finance (DeFi) platforms. DeFi platforms operate in a trustless and decentralized environment, which poses unique challenges for ensuring reliable identity verification. Existing solutions that rely on centralized authorities or reputation systems fall short in meeting the requirements of DeFi. Additionally, conventional authentication methods like usernames and passwords are vulnerable to various attacks, including phishing, credential theft, and account compromise. Consequently, there is a critical need to develop innovative and robust identity verification mechanisms specifically tailored to the decentralized nature of DeFi platforms. These mechanisms should effectively safeguard against identity attacks, particularly Sybil attacks, and ensure the integrity and trustworthiness of the DeFi ecosystem. Research hypothesis The research hypothesis aims to investigate the effectiveness and potential of biometrics as a security measure in mitigating Sybil attacks in DeFi. It can be formulated as follows: The integration of biometrics for identity verification in DeFi systems can effectively mitigate Sybil attacks and enhance the security of DeFi platforms. By examining the strengths, limitations, and practical implications of biometrics in DeFi, this research will contribute to the ongoing discussion on enhancing the security and credibility of DeFi systems. Research objectives The main objective of this research is to explore a comprehensive framework that integrates biometric-based identity verification to defend against Sybil attacks in DeFi. The specific research objectives are: To provide an overview of DeFi and its key concepts and principles. To compare and contrast DeFi with Centralized Finance (CeFi), highlighting the advantages and challenges of the decentralized approach. To explore the concept of Sybil attacks in the context of DeFi, including an understanding of their impact on DeFi systems. To review existing Sybil resistance approaches and assess their effectiveness. To investigate the role of biometrics in mitigating Sybil attacks in DeFi. To analyze the strengths and challenges of biometrics in the context of DeFi. To examine existing solutions and technologies in the field of biometric-based Sybil resistance. To explore the application of biometrics in various aspects of DeFi, such as decentralized lending, asset management, exchanges, and more. To discuss the challenges and limitations of implementing Sybil-resistant biometrics in DeFi. With the aim of enhancing security and trust in DeFil systems, the research endeavors to achieve these objectives by shedding light on Sybil attacks in the DeFi space and investigating the potential of biometrics as a viable solution. Through this exploration, the study seeks to contribute to a deeper understanding of these attacks and their implications within DeFi. Part I: Understanding Decentralized Finance (DeFi) DeFi has emerged as a groundbreaking paradigm in the realm of finance, leveraging blockchain technology and smart contracts to revolutionize traditional financial systems. DeFi represents a shift towards a more open, transparent, and inclusive financial ecosystem, enabling individuals to engage in various financial activities without relying on centralized intermediaries. In this part, we delve into the world of DeFi, exploring its fundamental principles, key characteristics, and the transformative potential it holds for the future of finance. Furthermore, we explore the advantages and challenges of DeFi. On the one hand, DeFi offers greater financial inclusion, accessibility, transparency, and privacy compared to traditional financial systems. On the other hand, DeFi faces obstacles such as scalability limitations, user experience complexities, regulatory uncertainties, security risks, and vulnerability to Sybil attacks. DeFi: An overview DeFi is an emerging sector within the blockchain and cryptocurrency ecosystem that aims to revolutionize traditional financial systems by providing open, permissionless, and decentralized alternatives (Chohan, 2021; Harvey, et al., 2021; Popescu, 2020; Schueffel, 2021; Zetzsche et al., 2020). At its core, DeFi seeks to democratize financial services, making them accessible to anyone with an internet connection and eliminating barriers to entry. DeFi platforms enable users to engage in a range of activities, including lending and borrowing, decentralized exchanges, liquidity provision, yield farming, asset management, and even complex financial derivatives. These services are typically implemented through decentralized applications (dApps) or protocols built on public blockchain networks like Ethereum (Buterin, 2014). Built on the principles of transparency, trustlessness, and immutability, DeFi leverages smart contracts and blockchain technology to enable various financial services without the need for intermediaries such as banks or financial institutions (Schär, 2021). Thus, financial transactions and interactions within DeFi platforms are recorded on the blockchain, providing a tamper-proof and auditable history of activities. Users can verify the integrity of the platform, track their transactions, and ensure that funds are managed securely. On top of that, smart contracts, self-executing contracts with predefined rules encoded on the blockchain, automatically execute transactions and enforce agreements, eliminating the need for intermediaries to oversee and validate the transactions. This automation ensures trust and transparency as the execution of transactions is based on predefined rules rather than subjective human judgment. One of the key features of DeFi is its emphasis on open-source software and interoperability. Developers can build upon existing DeFi protocols or create new ones, fostering a vibrant ecosystem of innovative financial solutions. This modular approach allows different DeFi applications to seamlessly interact with one another, enabling composability and creating opportunities for novel financial products and services. In recent years, DeFi has witnessed significant growth and adoption, with billions of dollars locked in various protocols and a vibrant ecosystem of developers, users, and investors. DeFi’s potential lies in its ability to provide financial services to underserved populations, offer greater financial inclusion and create new avenues for investment and wealth generation. To sum up, DeFi represents a paradigm shift in the way financial systems are designed and operated. By leveraging blockchain technology and smart contracts, DeFi aims to build a more open, accessible, and transparent financial ecosystem. As the sector continues to evolve, addressing DeFi issues like vulnerability to attacks, scalability, security, and regulatory challenges will be crucial to unlocking the full potential of DeFi and shaping the future of finance. Key concepts and principles of DeFi DeFi is built upon several key concepts and principles that define its fundamental characteristics and differentiate it from traditional financial systems. Understanding these concepts is essential for grasping the core philosophy behind DeFi and its transformative potential. The following are key concepts and principles that underpin DeFi: Decentralization Although the level of decentralization is still questionable (Aramonte, et al., 2021; Sun & Stasinakis, 2021; Barbereau, et al., 2022), DeFi emphasizes decentralization, distributing control and decision-making power across a network of participants rather than relying on a single centralized authority (Chen & Bellavitis, 2020; Popescu, 2020; Zetzsche, et al., 2020). By utilizing blockchain technology and smart contracts, DeFi platforms aim to remove the need for intermediaries and create trustless systems where transactions and agreements are executed autonomously based on predefined rules. Openness and permissionless DeFi platforms are open to anyone with an internet connection, ensuring inclusivity and equal access to financial services. They are permissionless, meaning users can participate without needing approval from intermediaries, such as banks or financial institutions. This allows individuals from around the world, including the unbanked or underbanked, to engage in financial activities without any barriers to entry. Transparency and audibility DeFi systems leverage the transparency and immutability of blockchain technology. Financial transactions, contracts, and activities are recorded on a public blockchain, providing an auditable and tamper-proof record of events. This transparency enables users to verify the integrity of the system, track their transactions, and ensure proper execution of agreements. Programmability DeFi introduces programmability to financial systems through the use of smart contracts (Cong & He, 2019; Kemmoe et al., 2020; Mik, 2017; Zheng et al., 2020). These programmable contracts enable the automation of financial processes, allowing for the creation of sophisticated and customizable financial products and services. With programmability, DeFi platforms can facilitate complex financial operations, such as automated lending and borrowing protocols, decentralized exchanges with automated market-making, and algorithmic trading strategies. Interoperability and composability DeFi platforms are designed to be interoperable, allowing different protocols and applications to seamlessly interact and share data. This interoperability facilitates composability, enabling developers to combine and build upon existing DeFi protocols to create new, innovative financial products and services. This composability promotes collaboration, efficiency, and rapid innovation within the DeFi ecosystem. User empowerment and ownership DeFi emphasizes user empowerment, enabling individuals to have direct control over their financial assets and data. Users have ownership of their private keys and are solely responsible for managing and securing their funds. This concept of self-custody ensures that individuals have full control over their assets without relying on intermediaries. Financial inclusion DeFi aims to foster financial inclusion by providing access to financial services for individuals who are traditionally underserved by traditional banking systems (Abdulhakeem & Hu, 2021). DeFi platforms can enable individuals in economically disadvantaged regions, without access to traditional banking services, to participate in savings, lending, and investment activities, thereby promoting greater economic empowerment. Financial innovation and experimentation DeFi encourages financial innovation by providing an environment that fosters experimentation and iteration. The open-source nature of DeFi protocols allows developers to build upon existing infrastructure, creating new financial products and services. This innovation extends beyond traditional financial instruments, enabling novel concepts such as decentralized stablecoins, tokenized assets, yield farming strategies, and decentralized insurance. DeFi’s permissionless nature empowers developers and entrepreneurs to explore new ideas and drive continuous evolution within the ecosystem. Community governance DeFi platforms often adopt decentralized governance models, enabling participants to collectively make decisions that impact the platform’s development and operations (Atzori, 2015; Bhambhwani, 2022; Zwitter, & Hazenberg, 2020). Through voting mechanisms, token holders can propose and vote on protocol upgrades, parameter changes, and other important decisions. Community governance enhances the platform’s decentralized nature and encourages active participation and alignment of interests among stakeholders. The collective advantages of DeFi play a crucial role in the increasing popularity and transformative potential of decentralized finance in revolutionizing the financial landscape. Concepts such as openness, decentralization, transparency, and user empowerment form the pillars of an inclusive financial ecosystem. When combined with programmability, trustlessness, security, and community governance, these principles drive financial innovation, encourage experimentation, and open doors to greater financial autonomy. DeFi is paving the way for a new era of financial possibilities, enabling individuals to have more control over their finances and fostering a dynamic and participatory financial environment. Decentralized Finance (DeFi) vs. Centralized Finance (CeFi) CeFi and DeFi represent two contrasting approaches to the provision of financial services (Qin, et al., 2021; Zetzsche & Anker-Sorensen, 2021). While both models aim to facilitate financial activities, they differ significantly in terms of their underlying structures, control, and overall philosophy. In CeFi, control and decision-making authority are held by centralized entities. Users must rely on these intermediaries to access financial services, leading to a hierarchical structure. Such platforms require users to meet eligibility criteria and often have limitations based on credit scores, documentation, or geographical location. DeFi, on the other hand, operates as a decentralized network, leveraging smart contracts and algorithms to automate financial processes. Users have greater control over their funds and assets, as transactions are executed according to predefined rules encoded in smart contracts. DeFi aims to reduce reliance on centralized authorities and enable trustless interactions. One of the key advantages of DeFi is its focus on accessibility and inclusion. Traditional financial systems can exclude individuals who lack traditional identification or reside in underserved regions. DeFi platforms aim to provide open and permissionless access to financial services, bridging the gap for the unbanked and underbanked populations. Transparency and security are also prominent features of DeFi. Transactions and activities within DeFi platforms are recorded on a public ledger, ensuring transparency and audibility. Smart contracts and cryptography secure funds and assets, reducing the risk of fraud or manipulation. However, identity attacks and vulnerabilities in smart contracts or external dependencies can pose risks if not properly addressed. Moreover, CeFi systems often require lengthy approval processes and compliance with regulatory frameworks, which can hinder innovation and limit the range of available financial products and services. Users are limited to the offerings provided by the centralized entities, with little room for customization or flexibility. DeFi, on the other hand, promotes innovation and flexibility by leveraging open-source technology and decentralized governance. Developers can create and deploy their own financial applications, protocols, and instruments within the DeFi ecosystem. This fosters a vibrant and competitive landscape where new ideas can flourish and users have a wide range of options to choose from. Additionally, the composability of DeFi protocols allows for the creation of novel financial products by combining existing ones, further driving innovation. In conclusion, the differences between CeFi and DeFi lie in their underlying structures, control, accessibility, transparency, security, and innovation. DeFi offers the potential to revolutionize the financial industry by providing inclusive, transparent, secure, and innovative financial services to a global population. Challenges and limitations of DeFi While DeFi offers several advantages over traditional financial systems, it also presents a set of unique challenges that need to be addressed for its widespread adoption and long-term sustainability (Amler et al., 2021; Carter & Jeng, 2021; Gudgeon et al., 2020; Li et al., 2022; Wang, et al., 2022). One significant challenge of DeFi lies in scalability. Most DeFi platforms are built on blockchain networks, such as Ethereum, which have inherent limitations in terms of transaction throughput and speed. As the popularity of DeFi continues to grow and user demand surges, scalability becomes crucial to ensure the seamless functioning of these platforms. Currently, blockchain networks face scalability constraints due to factors such as block size limitations, consensus mechanisms, and network congestion. Addressing scalability challenges necessitates the development of innovative solutions, such as layer 2 protocols, sharding, and off-chain scaling solutions. Extensive research and technological advancements are required to enhance the scalability of DeFi platforms, enabling them to handle a higher volume of transactions and support a broader user base. Another challenge in the realm of DeFi is the user experience and complexity associated with interacting with decentralized applications (DApps) and smart contracts. Non-technical users may find it challenging to navigate and understand the intricacies of DeFi platforms. Interacting with smart contracts often requires knowledge of wallet management, transaction fees, gas optimization, and private key security. The complexity and unfamiliarity of these processes can act as a barrier to entry, limiting the accessibility of DeFi platforms to a more technically inclined user base. Improving the user experience through intuitive user interfaces, simplified processes, and educational resources is crucial to broaden the adoption of DeFi among a wider audience. From a regulatory and compliance standpoint, DeFi operates in a relatively uncharted territory. The decentralized and global nature of DeFi platforms raises questions about regulatory oversight and compliance with existing financial regulations. Governments and regulatory bodies are still grappling with how to classify and regulate DeFi activities. The lack of clarity in regulatory frameworks can create uncertainty and hinder the development and adoption of DeFi platforms. Striking a balance between fostering innovation and ensuring compliance with applicable laws and regulations is a complex challenge. Collaborative efforts between industry stakeholders, policymakers, and regulatory bodies are required to establish clear guidelines and regulatory frameworks that facilitate the growth of DeFi while addressing potential risks such as money laundering, fraud, and investor protection. Security risks pose another critical challenge in the DeFi ecosystem. While blockchain technology provides inherent security features, DeFi platforms are not immune to vulnerabilities and risks. Smart contract bugs, code exploits, and hacking attempts can lead to significant financial losses for users. Additionally, the rapid development and deployment of new DeFi projects can result in insufficient security audits and due diligence. The complexity of DeFi protocols and the interconnectedness of various components within the ecosystem increase the attack surface and potential points of failure. Implementing robust security measures, conducting thorough code audits, promoting responsible development practices, and educating users about security best practices are essential to mitigate these risks and enhance the overall security posture of DeFi platforms. To sum up, DeFi faces several challenges that must be addressed to ensure its widespread adoption and long-term viability. Scalability limitations, user experience complexities, regulatory uncertainties, and security risks pose significant hurdles in the path of DeFi’s evolution. Overcoming these challenges requires continuous research, technological innovation, regulatory collaboration, and community-driven efforts. The future success of DeFi relies on our ability to tackle these challenges and cultivate a resilient and inclusive financial ecosystem. Part II: Sybil attacks in Decentralized Finance (DeFi) In this part, we delve into the topic of Sybil attacks in the context of DeFi. We begin by providing an overview of Sybil attacks, exploring the motivations and methods employed by malicious actors in orchestrating such attacks within the decentralized ecosystem. Understanding the nature of Sybil attacks is essential to grasp the potential impact they can have on the DeFi landscape. Next, we examine the far-reaching implications of Sybil attacks on DeFi systems. These attacks undermine the trust and fairness that underpin the decentralized principles of DeFi, creating a breeding ground for fraudulent activities, market manipulation, and financial losses for users and investors. Furthermore, we investigate existing solutions designed to mitigate Sybil attacks in DeFi systems. Overview of Sybil attack The Sybil attack is a type of malicious activity that poses a significant threat to the integrity and security of distributed systems. Coined in 2002, the term “Sybil” (Douceur, 2002) references the book “Sybil” written by Flora Rheta Schreiber, which portrays a case of multiple personality disorder. In the context of distributed systems, the Sybil attack involves the creation and control of multiple fake identities or nodes by a single malicious entity. These identities are designed to appear as legitimate entities within the system, allowing the attacker to manipulate the system’s behavior, disrupt its functionality, and compromise the trust among network participants. The main objective of the Sybil attack is to undermine the trust mechanisms and reputation systems that are crucial for the proper functioning of distributed systems. By creating a large number of Sybil identities, the attacker aims to influence decision-making processes, gain unfair advantages, or launch further attacks within the system. These attacks are particularly detrimental in peer-to-peer networks, social networks, online communities, and reputation-based systems, where trust and reputation play a vital role in establishing reliable interactions among participants. To execute a Sybil attack, adversaries employ various techniques and strategies. Identity fabrication is a common approach, where the attacker creates multiple fake identities, each with its own unique persona and characteristics. These fabricated identities can be designed to mimic genuine users, thereby deceiving the system and other participants. Collusion is another technique used by Sybil adversaries, wherein multiple fake identities are created and operated collectively to amplify the attacker’s influence or manipulate the system’s dynamics. Additionally, identity linkage refers to the process of establishing connections between different Sybil identities to enhance their credibility and deceive the system’s trust mechanisms. The consequences of a successful Sybil attack can be severe. It can lead to the degradation of system performance, compromised data integrity, and the erosion of trust among legitimate participants. Moreover, Sybil attacks can enable various other malicious activities, including spamming, spreading false information, Sybil-based routing attacks, and denial-of-service attacks. In the context of DeFi, the Sybil attack represents a significant threat to the security and trustworthiness of distributed systems. Its ability to exploit the vulnerabilities in trust mechanisms and reputation systems underscores the need for effective countermeasures. Sybils can interact with the system, participate in voting processes, manipulate governance decisions, and engage in fraudulent activities, jeopardizing the trust, fairness, and stability of DeFi systems. Impact of Sybil attacks on DeFi systems Sybil attacks can have profound implications for DeFi systems’ security, integrity, and trustworthiness. One of the primary impacts of Sybil attacks on DeFi systems is . DeFi platforms often incorporate decentralized governance models where token holders can participate in decision-making processes. Sybil attackers can create numerous fake identities and acquire a significant number of tokens to sway the voting outcomes in their favor. This enables them to control protocol upgrades, fund allocations, and other critical decisions, undermining the democratic nature of DeFi systems and potentially leading to biased outcomes. the manipulation of voting mechanisms and governance protocols Sybil attacks can also within DeFi platforms. Reputation plays a vital role in assessing the trustworthiness of participants and is often utilized to determine lending and borrowing privileges or access to other financial services. By creating multiple fake identities, Sybil attackers can artificially inflate their reputation scores, gaining undeserved privileges and access to resources. This not only distorts the reputation metrics but also undermines the fairness and effectiveness of DeFi systems in allocating resources based on merit. compromise the accuracy and reliability of reputation-based systems Another significant impact of Sybil attacks on DeFi systems is . DeFi platforms heavily rely on liquidity pools, where users contribute their assets for trading purposes. Sybil attackers can create fake identities and inject illiquid or worthless assets into these pools, thereby manipulating the market prices and causing financial losses for legitimate users. Additionally, Sybil attacks can be leveraged to manipulate the order book, execute front-running attacks, or carry out other forms of market manipulation, leading to unfair trading practices and financial instability. the disruption of liquidity pools and trading activities The financial implications of successful Sybil attacks on DeFi systems can be severe. Users may suffer financial losses due to manipulated voting outcomes, fraudulent reputation scores, or market manipulations. The overall trust and confidence in the DeFi ecosystem can also be eroded, deterring potential participants and investors from engaging with these systems. Consequently, Sybil attacks pose a significant threat to the growth and adoption of DeFi platforms, hindering their ability to provide efficient and transparent financial services. Efforts to develop robust defense mechanisms and strategies are crucial to protect the DeFi ecosystem and ensure its sustainability and continued growth. Existing Sybil resistance solutions Several approaches aim to prevent or mitigate the impact of Sybil attacks by implementing mechanisms that validate and verify the identities or activities of network participants. Centralized reputation systems One prevalent approach to combat Sybil attacks is the utilization of centralized reputation systems. These systems assign reputation scores to participants based on their behavior and interactions within the ecosystem. Participants with higher reputation scores are granted certain privileges or benefits within the platform. However, centralized reputation systems rely on trusted authorities or centralized entities to manage and assign reputation scores, which introduces vulnerabilities and undermines the core principles of decentralization. Furthermore, centralized reputation systems suffer from single points of failure. Malicious actors can target these centralized entities, compromising the reputation scores and distorting the trustworthiness assessment of participants. The reliance on trusted authorities contradicts the decentralized nature of DeFi and introduces a critical dependency on central entities that can be compromised or manipulated. Know Your Customer (KYC) KYC, or Know Your Customer, is the most common method of identity verification. It is a regulatory requirement in many countries that necessitates financial institutions and other regulated entities to confirm the identity of their customers. Most decentralized identity solutions require users to do KYC and provide PII, sensitive personal information like government ID, address, photo, etc. This information is then used to verify the customer’s identity using various methods, such as manual verification, electronic databases, and biometric authentication. The problem is that such solutions offer neither security nor privacy, storing users personal information in centralized servers, with direct access to the data given to appointed employees, meaning it can be potentially manipulated, lost, or stolen. To achieve minimal resistance to Sybil attacks, this approach utilized identity proxies such as phone numbers, credit cards, or IP address verification. It is often easy to obtain numerous identity proxies using techniques such as SMS or IP address spoofing. Furthermore, KYC processes can be expensive, and time-consuming as the customers must go through a series of steps to complete the verification process. Despite being a time-consuming process, KYC can still be inaccurate in verifying the customer’s identity due to software, human error or fraudulent documents. Additionally, the collection and storage of personal data during the KYC process can raise privacy concerns for customers. Another limitation of KYC is exclusion. It can exclude certain segments of the population who may not have the necessary documents to verify their identity, such as refugees or those without a permanent address. This exclusion can be detrimental to these populations and limit their access to financial services and other opportunities. The emergence of new technologies such as blockchain has the potential to revolutionize KYC by providing more efficient and secure identity verification mechanisms. By leveraging such cryptographic techniques, KYC can be streamlined and made more transparent, and secure, while also reducing the burden on customers. In 2020, Synaps’ startup initiated a user-friendly decentralized KYC solution to simplify fundraising and access to investment on the Web3. The project was created with the vision to optimize and streamline the identification path, making connected communities a safer place. Proof of Work (PoW) Proof of Work (PoW) is a consensus mechanism used in blockchain networks to achieve Sybil resistance (Baza et al., 2020; Platt & McBurney, 2023). It serves as a method to prevent malicious actors from creating multiple identities or controlling a majority of the network’s resources. In PoW, participants, known as miners, compete to solve complex mathematical puzzles, requiring significant computational power and energy consumption. The idea behind PoW as a Sybil resistance mechanism is that it is computationally expensive and time-consuming to solve these puzzles. This makes it impractical and costly for an attacker to generate multiple identities and control a significant portion of the network. The security of PoW lies in the fact that the majority of the network’s computational power is held by honest participants who follow the consensus rules. When a miner successfully solves a puzzle, they add a new block to the blockchain, which requires a substantial amount of computational effort. This block contains a record of transactions and is linked to the previous blocks, forming an immutable chain. This process makes it difficult for an attacker to modify or tamper with the existing blocks since they would need to redo the computational work for the affected blocks and catch up with the current chain length. The use of PoW as a Sybil resistance mechanism offers several advantages. Firstly, it provides a decentralized approach to achieving consensus, as the decision-making power is distributed among the participating nodes rather than concentrated in a central authority. Additionally, PoW has proven to be highly secure over the years, as it requires a substantial amount of computational power to override the consensus rules. However, PoW does have its limitations. The high energy consumption associated with PoW has raised concerns regarding its environmental impact. Additionally, PoW can result in longer transaction confirmation times and higher fees due to the computational effort required for block validation. Proof of Stake (PoS) Another approach to mitigate Sybil attacks in DeFi is the adoption of PoS mechanisms. PoS mechanisms require participants to stake a certain amount of tokens to gain voting power or influence within the ecosystem. The idea behind PoS is that participants who hold a significant stake in the network have a vested interest in its security and integrity, discouraging them from engaging in malicious activities. While PoS mechanisms have shown promise in deterring Sybil attacks, they are not foolproof. Determined attackers can still invest significant resources to create a large number of fake identities, diluting the influence of genuine participants and compromising the accuracy of decision-making processes. Moreover, PoS mechanisms rely on the assumption that participants’ economic incentives align with the security and integrity of the system. However, this assumption may not always hold true, as participants’ interests can diverge or be manipulated by external factors. Proof of Burn (PoB) Proof of Burn (PoB) is a Sybil resistance mechanism that can be used to prevent Sybil attacks in decentralized systems. In PoB, participants are required to “burn” or destroy a certain amount of cryptocurrency to gain access or influence within the system (Karantias et al., 2020). The concept behind PoB is that by burning cryptocurrency, participants demonstrate a tangible cost or sacrifice, making it economically prohibitive to create multiple fake identities or Sybil nodes. The idea is that someone who is willing to burn a significant amount of value has a genuine interest in the system’s integrity and is less likely to engage in malicious activities. In PoB, the burned cryptocurrency typically goes out of circulation, reducing the overall supply and potentially increasing the value of the remaining tokens. This can create a positive economic incentive for participants to engage honestly and contribute to the network’s security and stability. While PoB can be an effective Sybil resistance mechanism, it is important to consider its limitations and potential drawbacks. One challenge is determining the appropriate amount of cryptocurrency to burn and the criteria for access or influence within the system. Additionally, the burned tokens are permanently removed from circulation, which may have implications for the token’s liquidity and overall ecosystem. Web of Trust (WoT) The Web of Trust (WoT) is a trust model that can be used to establish the authenticity and reputation of individuals or entities within a network (Caronni, 2000; Rohit & Rifkin; 1997; Siddarth, et al., 2020; Shilina, 2023). The concept was first put forth by Pretty Good Privacy (PGP) creator Phil Zimmermann (1992). It was originally developed as a method for verifying the authenticity of email senders but has since been applied to other online activities such as website authentication and secure communication. Web of trust is a decentralized trust model and a cryptography concept used in PGP, GNU Privacy Guard (GnuPG), and other PGP-compatible systems. It is based on the ground of the authenticity establishment of the binding between a public key and its owner. In this model, each user has a trust rating that is determined by the ratings of other users they are connected to. The more trustworthy the user’s connections, the more trustworthy the user is perceived to be. This creates a decentralized system of trust that does not rely on centralized authorities or institutions. The WoT model’s decentralized nature allows for greater privacy and security. As the WoT relies on trust relationships between individuals, there is no central authority or single point of failure that could compromise the security of the system. However, the WoT model also has some limitations. For example, while promising, it has not yet been widely adopted in practice due to its usability challenges. WoT relies on the reputation and trustworthiness of individuals, but this can be difficult to establish, as individuals may have different criteria for what constitutes a trustworthy individual. The trust model of WoT has certain limitations since trust is subjective and varies between individuals. Additionally, the WoT model may be vulnerable to attacks by malicious actors who attempt to manipulate trust relationships in order to gain access to sensitive information or resources. On top of that, the effectiveness of WoT is limited to the size and activity of the network, as a larger network provides more opportunities for establishing trust and verifying identities. A good example here is the Kleros team’s Proof of Humanity protocol, a solution for identity combining WoT, with reverse Turing tests, and dispute resolution to create a Sybil-proof list of humans. The Proof of Humanity reputation-based WoT relies on users’ information about themselves utilized for verification. Humans who wish to be included in the registry submit photos, bios, and video recordings. This PII is stored using the IPFS (InterPlanetary File System). Registered profiles collect Democracy Earth’s UBI Tokens. Users who are already in the Proof of Humanity registry vouch for others registering with a certain amount of financial stake. By vouching, they guarantee that the users they vouch for exist and are not duplicates of another entry in the registry. To incentivize the maintenance of the registry, vouching deposits serve as a bounty, available for anyone able to correctly identify false positives in the registry. Social trust graphs Social trust graphs offer a promising approach to mitigating Sybil attacks by leveraging the connectivity characteristics of social networks. Several techniques have been developed to prevent Sybil attacks based on social trust graphs, including SybilGuard (Yu et al., 2006), SybilLimit (Yu et al., 2008), the Advogato Trust Metric, SybilRank (Cao et al., 2012), and sparsity-based metrics. SybilGuard and SybilLimit aim to limit the damage caused by Sybil attackers by considering the connectivity patterns of social graphs. These techniques analyze the trust relationships between participants and impose restrictions on the number of identities a single participant can create. The Advogato Trust Metric assigns trust levels based on endorsements from trusted individuals within the community. SybilRank uses random walks on social graphs to identify suspicious patterns that may indicate the presence of Sybil identities. The sparsity-based metric detects Sybil clusters in distributed reputation systems. Another example is BrightID, an identity system for the decentralized web. It solves the unique identity problem through the creation and analysis of a social graph. Its graph relationships are designed to identify true and Sybil identities based on the node’s position with respect to trusted seeds. BrightID uses a cross-network trust protocol built by graphically displaying social ties with the optional input of trusted seed IDs. The purpose of this protocol is to allow users to provide proof that they are not using multiple accounts in the same application. Reverse Turing tests Turing tests are a type of challenge-response test used to determine whether or not a machine can exhibit human-like intelligence. The Turing test originally called the imitation game was introduced by British mathematician and computer scientist Alan Turing (1950) in his paper ‘Computing Machinery and Intelligence’ while working at the University of Manchester. Turing tests typically involve a human evaluator who engages in a conversation with a machine and tries to determine whether the responses are being generated by a human or a machine. Reverse Turing tests are Turing tests in which the objective or roles between computers and humans have been reversed. They have been used in a variety of contexts, including as a means of authentication for online systems. In this context, reverse Turing tests are often used to verify that a user attempting to access a system is indeed human and not a machine or bot. This type of test is commonly known as a CAPTCHA (Completely Automated Public Turing Test to Tell Computers and Humans Apart). The use of CAPTCHAs as a means of preventing automated access to online systems has become widespread in recent years, due to the increasing prevalence of bots and other automated tools that can be used for malicious purposes such as spamming or denial-of-service attacks (Von Ahn et al., 2003). Despite their widespread use, reverse Turing tests and CAPTCHAs have been subject to various criticisms and limitations. Some researchers have questioned the ability of reverse Turing tests to verify the user’s real-world identity or prevent identity fraud, while others have noted the increasing sophistication of bots and automated tools that can bypass CAPTCHAs. Additionally, CAPTCHAs have been criticized for being difficult for some users to complete, particularly those with visual or cognitive impairments. For instance, the Idena blockchain, an open-source project created by an anonymous group of engineers in 2018, is driven by eco-friendly Proof-of-Person consensus where each node is associated with a crypto identity representing a single individual with equal voting power (Subira-Nieto, 2021). The Idena Network achieves Sybil resistance by combining human-generated reverse Turing tests, also known as FLIP tests — CAPTCHAs, with elements of a virtual pseudonym party. Every unique human can become an Idena validator. To start mining, they only need to prove you are a unique human, without disclosure of any personal data. Idena users must attend live authentication ceremonies held simultaneously for the entire network frequency is determined by the size of the network. During these synchronous events, they must complete the FLIP test suite within a limited amount of time. After that, users must create new tests. The time limit prevents a single person from solving more than one set of FLIPs, while the human-generation aspect provides machine-learning resistance. In addition, the protocol protects privacy because it does not include any data other than evidence of conscious cognitive ability. The most notable flaw of the Idena design is the significantly higher coordination overhead to achieve a repetitive concurrent FLIPS solution. All Idena nodes must constantly participate in synchronous events, otherwise, their identities will expire. Application-specific defenses Several initiatives have been developed to address the issue of Sybil attacks and provide protection against them. Here are a few notable examples: Gitcoin Passport acts as an aggregator of decentralized society credentials, proving users’ trustworthiness without needing to collect personally identifiable information. Gitcoin Passport is a self-sovereign data collection protocol built with the Ceramic Network, created in line with the Decentralized Identifier (DID) and VC specifications. This data is intended for broad interoperability for any system that wishes to issue or consume VCs to establish the ‘unique humanity’ of an individual through their direct ownership of multiple accounts (Twitter, BrightID), or Web3 assets (ENS). The Gitcoin Passport team continually expands what stamps Passport holders can collect. Stamps represent a web3 citizen’s participation in various groups and communities. Gitcoin Passport: Upala is a decentralized digital identity solution that also functions as an anti-Sybil framework for dApps, quality control and unification layer for other identity systems. In a nutshell, the Upala project offers a unique approach to digital identity verification through its use of a digital identity uniqueness score, measured in dollars (Price of forgery in Upala terms). The price of forgery is generated through market dynamics enforced by the protocol. Upala is composed of groups that can consist of anyone, including friends, work communities, DAO members, or even entire identity systems. A user can apply to become a member of different groups. Upala: : SumUp is a Sybil-resistant algorithm specifically designed for online content recommendation and voting systems. It utilizes a trust-based approach to mitigate the impact of Sybil attacks on the accuracy of recommendations and voting outcomes. SumUp DSybil is another Sybil-resistant algorithm that focuses on maintaining the integrity of voting systems (Yu et al., 2009). It employs a decentralized voting protocol that incorporates social trust relationships to identify and filter out Sybil attackers. DSybil: Whānau is a distributed hash table (DHT) algorithm that includes mechanisms to prevent and detect Sybil attacks. It leverages a structured overlay network and employs cryptographic techniques to ensure the authenticity and uniqueness of participating nodes. Whānau: Kademlia, a popular distributed hash table protocol, has been implemented in the I2P (Invisible Internet Project) network with additional provisions to mitigate Sybil attacks (Maymounkov & Mazieres, 2002). These provisions enhance the protocol’s resistance against Sybil nodes attempting to manipulate the network. Kademlia in I2P: These protocols demonstrate different approaches to address the challenges posed by Sybil attacks in various distributed systems. By incorporating trust-based mechanisms, decentralized voting protocols, or cryptographic techniques, they aim to maintain the integrity, security, and reliability of the underlying networks. It is important to note that not all the aforementioned mechanisms can fit the DeFi framework. On top of that, the effectiveness of Sybil resistance approaches may vary depending on the specific DeFi platform and its design. Different protocols may prioritize different Sybil resistance mechanisms based on their unique requirements and considerations. To address the limitations of current solutions, it is clear that innovative approaches are required to enhance the security of DeFi platforms against Sybil attacks. In the following sections, we suggest incorporating biometric-based identity verification as a promising solution to strengthen the resilience and trustworthiness of DeFi ecosystems. Through the use of decentralized mechanisms and robust biometric techniques, our goal is to establish a more effective defense against identity attacks and bolster the overall security of DeFi. Part III. Biometrics and identity verification In this part, we delve into the topic of biometrics and identity verification, exploring its various aspects and implications. We begin with an introduction to biometrics, highlighting its significance in the field of authentication and identity verification. We then discuss the strengths and challenges of biometrics. Furthermore, we explore existing solutions in the field of biometric verification. This analysis will contribute to the broader discussions surrounding biometric technologies and their implications for security, privacy, and user experience in various domains. Introduction to biometrics Biometrics refers to the measurement and analysis of unique physical or behavioral characteristics of individuals (Jain & Kumar, 2010; Bolle et al., 2013; ). It is a field that focuses on using these distinctive traits to identify, verify, and authenticate individuals. Biometric systems have gained significant attention and adoption in various sectors, including security, identity management, access control, and authentication, and advanced in recent years (Choudhury et al., 2018; Raju & Udayashankara, 2018; Raheem, 2019; Venkatesan & Senthamaraikannan, et al., 2018). The fundamental principle behind biometrics is that each person possesses distinctive physiological or behavioral characteristics that are unique to them (Kaur & Verma, 2014). These characteristics can include fingerprints, iris patterns, facial features, voice patterns, hand geometry, gait, and even behavioral traits like typing rhythm or signature dynamics. Biometric systems capture and analyze these traits to create biometric templates or digital representations that can be used for identification or verification purposes. The process of utilizing biometrics typically involves several stages. First, during enrollment, an individual’s biometric data is captured using specialized devices such as fingerprint scanners, iris scanners, or facial recognition cameras. The data is then processed to extract key features and convert them into a standardized format that can be stored and compared efficiently. For identification, biometric systems compare the captured biometric data against a database of pre-registered templates to determine the identity of the individual. In verification scenarios, the biometric data is compared against the template of a specific individual to confirm their identity. The comparison process involves matching algorithms that analyze the captured biometric data and compare it to the stored templates, considering factors such as similarity scores or thresholds to determine a match or non-match. Strengths and challenges of biometrics Biometrics offers several strengths and faces certain challenges in its implementation. One of the primary strengths is biometrics’ strong security (Jain, et al., 2006). Unlike traditional identity verification and authentication methods such as passwords or e.g. PINs, biometric traits are unique to each individual. This uniqueness makes it difficult for unauthorized users to replicate or forge biometric data, significantly enhancing security. Additionally, biometrics provides convenience and a seamless user experience. Users no longer need to remember and manage multiple passwords or carry physical tokens. Instead, they can simply use their biometric traits, such as fingerprints or facial features, to authenticate themselves. This convenience reduces friction and enhances user satisfaction. Biometric systems also incorporate advanced anti-spoofing techniques, making it challenging for malicious actors to spoof or trick the system using fake or replicated biometric data. These techniques ensure the authenticity of the captured biometric traits, further strengthening the security of the authentication and verification processes. Furthermore, biometrics is scalable and flexible. It can accommodate a large number of users without requiring significant infrastructure changes. Biometric systems can be seamlessly integrated into various devices and platforms, allowing for flexible deployment across different applications and industries. However, biometrics also faces challenges that need to be addressed (Down & Sands, 2004; Ross et al., 2019). One major challenge is privacy concerns (Woodward, 1997). The collection and storage of biometric data raise questions about data protection and potential misuse. Proper measures, including data encryption and compliance with privacy regulations, must be in place to safeguard individuals’ sensitive information. The accuracy and reliability of biometric systems can also be a challenge. Factors such as environmental conditions, device quality, and the quality of the captured biometric samples can impact the accuracy and performance of the system. False acceptance or rejection rates can vary, necessitating continuous improvement and fine-tuning of the technology. Additionally, the irrevocability of biometric traits poses a challenge. Once a biometric template is compromised or stolen, it cannot be easily changed or revoked. Individuals may face difficulties in re-establishing their identity or revoking access in such cases. Cultural and physical limitations also exist in the field of biometrics. Some biometric traits may be less suitable for certain populations or individuals with physical disabilities. For example, fingerprint recognition may not work well for individuals with worn or scarred fingerprints, and facial recognition may face challenges with accuracy for individuals from diverse racial or ethnic backgrounds. Lastly, integrating biometrics into existing systems and ensuring interoperability across different platforms can be complex. Establishing standards and protocols is necessary to facilitate seamless integration and data exchange between different biometric systems (De Hert, 2005). * There are False acceptance rate (FAR) that occurs when a biometric system incorrectly identifies an unauthorized person as an authorized one, and False rejection rate (FRR) that occurs when a biometric system incorrectly rejects an authorized person as an unauthorized one. **Imposter attack is a type of attack where an imposter presents a fake biometric sample (e.g., a photo, a voice recording, or a fingerprint) to the system in order to gain unauthorized access. A spoof attack is a type of attack where an attacker uses a fake biometric sample that mimics the characteristics of a real sample (e.g., a 3D-printed fingerprint or a silicone mask) to trick the system. Addressing these challenges requires ongoing research, technological advancements, and adherence to privacy and security best practices. Despite these challenges, biometrics holds significant potential in enhancing security, convenience, and user experience in various applications. Biometrics x blockchain technology In the context of DeFi, where the focus is on providing financial services using blockchain technology, biometric verification solutions can play a vital role in enhancing security and user experience. While specific implementations may vary, some promising solutions have appeared at the intersection of blockchain and biometric technology. : Anima decentralized identity (dID) protocol allows users to decentralize their identity and share Verified Credentials (VCs) as they see fit. Anima’s solution is multichain, it is compatible with every EVM chain and the team almost finished the integration with Cosmos. Recently, the Anima protocol went live on BNB and bridged all identity use cases — from confirming personhood members to meeting regulatory requirements. The Anima PoP helps ensure that the community members are unique and human, which helps prevent Sybil attacks and maintains community integrity. By leveraging Anima, anyone can develop a more secure and user-friendly authentication system on their dApps that prioritize user privacy and trust. Anima protocol uses VCs issued by Synaps to link users’ decentralized IDs to their crypto wallets, employing blockchain encryption and wallet signatures for optimal security. The protocol securely stores the VCs, while identity attributes such as names, nationality, and biometric data are kept in a decentralized data storage system called Storj. Anima : Governor DAO is a decentralized autonomous organization positioned as the ‘DAO of DAOs’. Governors offer a suite of products and services for projects looking to build DAO qualities in their communities. Such offerings include a Sybil resistance product for one-voice-one-vote governance and governance bootstraps for new communities, consultations, and smart contract porting. Governor Decentralized Autonomous Organization (GDAO) allows founders and core team members to hold fewer legal liabilities and offer more open-based ‘Sandbox-like’ services in DeFi, decentralizing project ownership. Driven by its biometrically verified proof-of-existence token, GDAO aims to be a role model for other DAOs. Utilizing biometrics, Governor DAO PoP identity verification is achieved by biometric voice/facial recognition. All biometric information is encrypted as it is produced and is never stored. In particular, in partnership with biometrics firm Finnovant, Governor DAO has created a portal for biometric authentication of Ethereum wallets. Users enter the portal with a Web3-connected wallet and input face + voice readings. Locally, the user device runs the input information through hundreds of algorithmic indicators to create an encrypted output hash representing the individual. The project is also subject to privacy concerns since the biometric data is not enough secured. Governor DAO : Humanode is the crypto-biometric L1 blockchain where 1 human = 1 node that brings Sybil resistance, proper per-human distribution of power and innovative governance models to Web3 using crypto-biometric technology (Kavazi et al., 2021). The Humanode network bases its infrastructure on human biometrics. Instead of PoW and PoS, Humanode utilizes the combination of proof of uniqueness and proof of existence. Combined with blockchain, it creates the first-ever human-based digital verification layer. The validators who run the Humanode blockchain are created through private crypto-biometric authentication which is a combination of cryptographic and hardware privacy with matching and liveness detection mechanisms to verify the uniqueness and existence of real human beings. One unique human who is alive can create only one node, and each node has one vote in the system. All the system cares about is if a user is a unique human being and if a user is alive. Humanode utilizes advanced liveness detection technology, due to which the possibility of spoofing an identity without a real human in front of the camera is 1 of 80K (biometrics accuracy is one of the fastest growing areas as it was 1 of 12.5K only ten years ago, in 2012). To achieve the highest accuracy in the biometric industry, 1 in 125M false acceptance rate — FAR, while providing privacy, the project currently implements FaceTec’s biometrics and liveness as well as AMD SEV SNP secure enclaves with the attestation from the chain. The main drawback here is Humanode’s limited chain scalability, up to 10,000 unique human validators, and yet hardware-dependent privacy, which is still better than how biometric data is handled by centralized entities. Humanode : Worldcoin is an open-source identity and financial network on a mission for a global distribution ecosystem for a universal basic income (UBI). Basically, the Worldcoin blockchain introduces a new PoP system that consists of a database of users’ scanned irises that are used to validate their identities and prevent the network from Sybil attacks and users from creating multiple accounts (Gent, 2023). From a technical point of view, Worldcoin will use a Layer 2 network and run on top of the Ethereum blockchain. This enables compatibility with many existing tools and services. The main drawback of Worldcoin is an absence of a clear privacy scheme and unproven accuracy, and statements that the team built its biometric database from the bodies of the poor. Worldcoin * All data is presented as of July 2023. When it comes to DeFi, Humanode stands out as a highly relevant project in the field. Humanode recognizes the importance of addressing the challenges posed by Sybil attacks in the DeFi space. By leveraging biometric-based Sybil resistance mechanisms, Humanode aims to enhance the security and trustworthiness of DeFi platforms. The Humanode’s process of identifying a person using biometric templates can be easily applied to DeFi platforms, offering such important perks as high accuracy, enhanced privacy and security. Biometrics adds an additional layer of security to the Sybil resistance mechanisms in DeFi. By linking each user’s biometric traits to their digital identity, it becomes significantly more difficult for malicious actors to create multiple fake accounts or impersonate legitimate users. Biometric verification can be used during critical interactions, such as accessing funds, executing transactions, or participating in governance processes, to ensure that only authorized individuals with verified biometric traits can perform these actions. In general, Humanode’s bio-authentication process is divided into three stages: The user scans his face for 10–15 seconds with any device over a 3mpx camera. The neural network transforms the video feed into an anonymized 3D template while other modules check if the person in front of the camera is a real one. The biometric template and liveness data are encrypted and sent to the biometric confidential servers. Confidential biometric servers immediately delete the liveness data and compare a new anonymized 3D template against those already registered in the system. They send the reply in the form of a unique ID to the Humanode chain or directly to an application. Every user authentication requires two pieces of data: anonymized 3D template (for matching) and liveness data (to prove the face data was collected from a live person). Liveness data must be timestamped, valid for a certain time, and then removed. Only an anonymized 3D template is saved in the confidential VM for a period of no longer than one year. For each authentication attempt, new liveness data must be acquired. Face data is encrypted and stored separately from the associated liveness data to avoid creating a honeypot risk. Mainly, Humanode’s dedication to exploring the potential of biometric-based Sybil resistance mechanisms positions it as a highly relevant and impactful project within the realm of DeFi. Part IV. Biometric-based Sybil resistance for DeFi In this section, we explore the potential of biometric-based Sybil resistance mechanisms for DeFi applications. By leveraging biometric techniques, DeFi platforms can enhance security, mitigate identity attacks, and provide a more robust and trustworthy financial ecosystem. Basically, we examine various DeFi use cases where biometrics can play a crucial role in ensuring the integrity and authenticity of user identities. The main benefits of biometric-based approaches for DeFi Biometric-based approaches have the power to bring Sybil resistance for DeFi, they offer several benefits that contribute to the overall improvement of security, trust, and user experience within DeFi systems. Here are some common benefits related to the majority of DeFi applications: Stronger users identity verification Biometrics provides a more reliable means of verifying the identity of individuals. Utilizing biometric liveness detection, facial recognition, or multimodal biometric approaches the system can establish a higher level of confidence in the user’s identity, mitigating the risk of Sybil attacks. Enhanced security and resistance to Sybil Attacks Biometric traits are difficult to replicate or forge, providing a higher level of security compared to traditional authentication and verification methods. By ensuring that each participant has a unique biometric identity, the risk of Sybil attacks and unauthorized access to funds or sensitive information can be significantly reduced. Improved trust and accountability Biometric-based mechanisms help establish a stronger sense of trust and accountability within the DeFi ecosystem. Participants can have confidence that the identities associated with transactions or governance actions are genuine and verified, reducing the likelihood of fraud or manipulation. Promotion of real decentralization and democracy Biometrics have the potential to contribute to real decentralization and democracy in DeFi by addressing the issues associated with stakers in Proof-of-Stake (PoS) systems and mining cartels in Proof-of-Work (PoW) systems. It can introduce a more equitable distribution of power and resources. This approach ensures that no individual or entity can exert disproportionate control or influence over the network. By using biometrics to verify identities and limit participants to a single vote and node, the DeFi networks can uphold the values of equality, fairness, and inclusivity. User-friendly experience Biometrics simplifies the user experience by eliminating the need for complex passwords or multiple steps. Users can conveniently access their accounts, perform transactions, and engage in DeFi activities using their biometric traits, leading to a more seamless and user-friendly experience. Elimination of password-related risks Traditional authentication methods, such as passwords, are vulnerable to risks like weak passwords, password reuse, or password theft. Biometrics eliminates these risks altogether since users rely on their unique biometric traits, which are more secure and difficult to compromise. This reduces the likelihood of unauthorized access or account breaches due to password-related vulnerabilities. Moreover, biometric processes align well with the increasing usage of mobile devices for online transactions. Most modern smartphones and tablets are equipped with biometric sensors, enabling users to conveniently authenticate themselves using their features. These mobile-friendly authentication and verification methods cater to the growing trend of mobile-centric user interactions in DeFi. Financial inclusion Biometrics can contribute to financial inclusion by providing access to decentralized financial services for individuals who may not have traditional identification documents or formal banking relationships. By leveraging biometrics, DeFi platforms can extend their reach to underserved populations and offer opportunities for financial empowerment. Differentiation and competitive advantage Integrating biometric-based authentication and verification techniques into DeFi platforms can provide a unique selling proposition and a competitive advantage. By offering enhanced security, convenience, and privacy, DeFi services can attract users who prioritize these aspects. This can lead to increased user acquisition, retention, and overall platform growth. Efficient resource allocation By preventing the creation of double accounts, the platform can optimize resource allocation. This includes server space, customer support, and other resources that would have been unnecessarily duplicated if multiple accounts were allowed per person. It helps streamline operations and potentially reduces costs for the platform. Compliance with regulations Biometric-based identity verification aligns with regulatory requirements, such as Know Your Customer (KYC) and Anti-Money Laundering (AML) regulations. By integrating biometric technology, DeFi platforms can enhance their compliance measures and contribute to the overall integrity of the financial ecosystem. Through its cutting-edge research and development efforts, projects like Humanode aim to introduce biometric-based Sybil resistance solutions across various DeFi use cases that include decentralized lending and borrowing, decentralized asset management, decentralized exchanges (DEXs), decentralized governance, yield farming and staking, and many others. Integrating biometrics into these DeFi applications, Humanode seeks to improve the overall security, privacy, and user experience within the DeFi ecosystem. Reducing the possibility of Sybil attacks and ensuring a more robust identification process, Humanode contributes to the advancement and adoption of DeFi as a secure and trustworthy financial system. Benefits of biometric-based Sybil resistance for DeFi applications Biometric-based Sybil resistance for DeFi offers various benefits across different use cases within the decentralized finance ecosystem. Let’s explore some of these benefits in specific use cases: Decentralized lending and borrowing Decentralized lending and borrowing as a key DeFi use case, operates on a blockchain without the need for traditional intermediaries such as banks. In a nutshell, it allows individuals to lend or borrow digital assets directly from other participants within the decentralized lending ecosystem (Paliwal, 2022; Saengchote, 2022). In decentralized lending, individuals can lend their digital assets, such as cryptocurrencies, to borrowers in exchange for earning interest on their loans. Lenders have the opportunity to earn passive income by providing liquidity to the lending pool. Borrowers, on the other hand, can access loans without the need for a credit check or collateral, as the lending process is facilitated by smart contracts that enforce the terms and conditions of the loan. Decentralized lending platforms typically use algorithmic protocols to determine interest rates and match lenders with borrowers. These protocols ensure transparency, fairness, and efficiency in the lending process. Interest rates are determined by supply and demand dynamics, and borrowers can choose from a wide range of lending options available on the platform. Overall, decentralized lending and borrowing provide individuals with greater financial freedom, increased accessibility to capital, and the potential for higher returns on their digital assets, all while bypassing the need for traditional intermediaries. Bometric-based identity verification mechanisms implemented into decentralized lending and borrowing platforms have the potential to bring significant benefits. Thus, by leveraging biometrics, DeFi platforms like Aave and Compound can enhance anti-fraud measures and the trustworthiness of user identities, mitigating the risks associated with Sybil attacks. This, in turn, can positively impact the lending and borrowing processes in several ways. Biometric-based Sybil resistance adds an additional layer of security by requiring users to authenticate their identity using their unique biometric traits. This prevents unauthorized access to user accounts and mitigates the risk of fraudulent activities, ensuring that only legitimate users can engage in lending and borrowing transactions. Biometric-based verification instills a higher level of trust and confidence among participants in the DeFi lending and borrowing ecosystem. Lenders can be more confident that they are interacting with genuine borrowers, minimizing the risk of lending to fraudulent or unreliable entities. Similarly, borrowers can have greater assurance that they are engaging with trustworthy lenders, reducing the likelihood of falling victim to scams or unethical lending practices. This increased trust fosters a more secure and efficient lending and borrowing environment within the DeFi ecosystem. Needless to say, biometric authentication offers a seamless and convenient user experience, eliminating the need for users to remember and manage complex credentials, enhancing the user experience, and making it easier for individuals to participate in lending and borrowing activities. Decentralized asset management Decentralized asset management is an innovative approach to managing and investing in various types of assets without relying on traditional centralized intermediaries (Chohan, 2021; Harvey, et al., 2021; Popescu, 2020; Schueffel, 2021; Zetzsche et al., 2020). It operates on blockchain networks, providing a decentralized infrastructure where participants can create, manage, and trade digital assets. Decentralized asset management platforms leverage smart contracts to automate various functions, including investment strategies, asset allocation, and profit distribution. This automation ensures that investment decisions are executed transparently and without the need for human intermediaries. One of the key benefits of decentralized asset management is increased accessibility and inclusivity. These platforms enable anyone with an internet connection and a digital wallet to participate in asset management, regardless of their geographical location or financial background. Furthermore, decentralized asset management platforms often provide enhanced liquidity compared to traditional systems. The use of blockchain technology enables assets to be tokenized, meaning they are represented as digital tokens on the blockchain. These tokens can be easily traded and exchanged on decentralized exchanges, providing users with increased flexibility to manage their investments and access liquidity when needed. Biometrics has the potential to offer substantial benefits to decentralized asset management within the realm of DeFi. It enhances user identity verification, improves security and fraud prevention, fosters trust and transparency, and provides a seamless user experience. While integrated into existing platforms they can easily scale to accommodate a growing user base. Biometrics can also be interoperable with various devices, such as smartphones or biometric hardware, making it accessible to a wide range of users without the need for additional authentication and verification methods. Biometric-based identity verification can be designed to protect user privacy by employing encryption, zero-knowledge proofs, et cetera. This ensures that sensitive biometric data is securely stored and cannot be reverse-engineered to reconstruct the original biometric information. By protecting user privacy, decentralized asset management platforms can build trust with their users and adhere to privacy regulations. Decentralized exchanges (DEXs) Decentralized exchanges (DEXs) are an integral part of the DeFi ecosystem and represent a fundamental shift in how cryptocurrency trading is conducted. Unlike traditional centralized exchanges, DEXs operate on blockchains, allowing users to trade digital assets directly with one another without the need for intermediaries (Lehar & Parlour, 2021; Lo & Medda, 2021; Mohan, 2022; Han et al., 2021; Warren & Bandeali, 2017). One of the key advantages of DEXs is the elimination of the need to trust a central authority with custody of funds. In traditional exchanges, users typically deposit their assets into a centralized wallet held by the exchange, relinquishing control over their funds. However, DEXs enable users to retain control of their assets at all times. Trades on DEXs are executed using smart contracts, which automate the process and ensure the secure transfer of assets directly between participants. An important feature of DEXs is their ability to foster greater privacy and anonymity. Traditional exchanges often require users to go through a lengthy registration process, including identity verification and Know Your Customer (KYC) procedures. DEXs, on the other hand, typically do not require users to provide personal information or undergo KYC checks, allowing for pseudonymous trading. This privacy-enhancing feature appeals to individuals who value their financial privacy and want to maintain control over their personal information. DEXs also promote market efficiency and liquidity by enabling peer-to-peer trading. Liquidity on centralized exchanges depends on the availability of buyers and sellers at any given time. In contrast, DEXs leverage liquidity pools and automated market-making algorithms to facilitate trades, ensuring that assets can be bought or sold even when there might be a lack of direct counterparties. This liquidity is achieved through users’ participation in providing liquidity to the pool, allowing them to earn fees in return for their contribution. Moreover, DEXs contribute to the democratization of finance by providing access to a wide range of digital assets. Traditional exchanges often have listing requirements and fees that may limit the availability of certain assets. DEXs, being open and permissionless, allow for the listing of various tokens and enable users to trade directly without gatekeepers. This creates opportunities for individuals to access and invest in a more diverse set of assets, including emerging cryptocurrencies and tokens associated with specific DApps. Limiting users to one account on a DEX promotes fairness and equal opportunities for all participants. It prevents individuals from creating multiple accounts to gain unfair advantages, such as front-running or market manipulation. This ensures a level playing field for all users, fostering trust and integrity within the DEX ecosystem. Biometric authentication adds extra perks to popular DEX platforms like Curve and dYdX. For example, DEXs operate on a non-custodial model, where users have direct control over their funds without relying on a central authority, and biometrics can add an additional layer of security to this model by ensuring that only the authorized user can access and execute transactions on their DEX account. This helps prevent unauthorized access, funds theft, or unauthorized trades. Traditional authentication methods, such as passwords or private keys, can be prone to human error. Users may forget their passwords, misplace their private keys, or accidentally share sensitive information. Biometric authentication eliminates these risks and ensures a more reliable and error-free authentication process. Basically, biometric-based identity verification enhances the overall trustworthiness and security of DEXs. When users feel confident that their accounts are well-protected, they are more likely to engage in trading activities and explore the platform’s offerings. This increased trust can lead to higher user adoption rates and contribute to the growth of the DEX ecosystem. Decentralized marketplaces Decentralized marketplaces represent a significant innovation in the world of e-commerce, enabling peer-to-peer transactions. The key advantage of decentralized marketplaces is the removal of middlemen. In traditional online marketplaces, intermediaries such as e-commerce platforms or payment processors facilitate transactions and charge fees for their services. However, decentralized marketplaces allow participants to interact directly with one another, eliminating the need for middlemen. This direct interaction streamlines the buying and selling process, reduces costs, and allows for a more efficient allocation of resources. It is known that decentralized and NFT marketplaces also offer increased transparency. Transactions conducted on blockchain-based platforms are recorded on a public ledger, ensuring that all participants have access to the same information. This transparency reduces the risk of fraud and provides buyers and sellers with a verifiable record of transactions. Additionally, smart contracts automatically enforce the terms and conditions of transactions, enhancing trust and reducing the need for legal interventions. Another important feature of decentralized marketplaces is the empowerment of individual sellers. In traditional marketplaces, sellers often face strict listing requirements, high fees, and limited control over their own products. Decentralized marketplaces, however, provide a more open and inclusive environment, allowing sellers to list their products or services directly and retain greater control over pricing, inventory management, and customer relationships. This enables small businesses and independent sellers to reach a global audience and compete on a more level playing field. Decentralized marketplaces also promote financial inclusion. By leveraging blockchain technology, these marketplaces can facilitate cross-border transactions and provide access to financial services for individuals who are underserved by traditional banking systems. Participants can transact using crypto, which offers lower transaction fees and faster settlement times compared to traditional payment methods. Biometrics can offer privacy advantages for decentralized marketplaces. Unlike traditional identification methods that may require users to share personal information or sensitive data, biometric verification can be designed in a way that preserves user privacy. Having one account linked to the user’s biometrics allows for more efficient customer support interactions. When the user contacts customer support, their identity can be quickly verified using their biometric traits, saving time and ensuring a smoother support experience. Furthermore, with biometrics, users are less likely to face account recovery issues that may arise from forgotten passwords, lost private keys, or compromised recovery emails. Since biometrics are tied directly to the user, account recovery becomes more streamlined and less reliant on complex recovery processes. This saves time and effort for both users and marketplace administrators. On top of that, biometric-based verification implemented in decentralized and NFT marketplaces instills confidence in users regarding the security and integrity of these platforms. When users feel that their accounts and transactions are well-protected, they are more likely to engage in buying, selling, or trading activities on the platform. This increased user confidence can lead to higher adoption rates and contribute to the success of the decentralized marketplace ecosystem. After all, integrating biometric-based verification into decentralized marketplaces can provide a unique selling proposition and a competitive advantage. By offering enhanced security, convenience, and privacy, marketplaces can attract users who prioritize these aspects. This can lead to increased user acquisition, retention, and overall marketplace growth. Decentralized governance Decentralized governance is a groundbreaking concept that has emerged within the realm of decentralized systems, such as blockchain networks and decentralized organizations (DAOs). It represents a shift away from centralized decision-making structures and empowers participants to collectively govern and shape the rules and direction of the system (Atzori, 2015; Bhambhwani, 2022; Zwitter, & Hazenberg, 2020) In traditional centralized governance models, decisions are made by a central authority or a select group of individuals who hold power and influence. This can often lead to issues such as a lack of transparency, potential for corruption, and limited participation from the broader community. Decentralized governance seeks to address these challenges by distributing decision-making authority among a network of participants. At the core of decentralized governance is the principle of consensus. Participants in a decentralized system come together to discuss and propose changes or improvements to the system. These proposals are typically made through a transparent and open process, allowing participants to voice their opinions and concerns. The decision-making process often involves mechanisms such as voting, signaling, or staking, where participants can express their preferences and collectively determine the outcome. Blockchain technology plays a vital role in enabling decentralized governance. By utilizing smart contracts and distributed ledgers, the decision-making process becomes transparent and verifiable. Smart contracts can automate the execution of governance rules, ensuring that decisions are implemented as intended. Additionally, the immutability and tamper-resistant nature of blockchain technology enhances the trust and security of the governance process. A key advantage of decentralized governance is that it encourages innovation and adaptability. Participants can propose and implement changes quickly, allowing the system to respond to evolving needs and challenges. Decentralized governance relies on trust and transparency among participants. Biometric verification strengthens this trust by providing a robust and tamper-resistant method of verifying individual identities. This helps ensure that decisions are made by legitimate stakeholders, fostering transparency and accountability within the governance system. Furthermore, biometric verification implemented in DAOs can enhance the security and integrity of voting processes in decentralized governance systems. By implementing biometric-based verification, participants can securely verify their identities, ensuring that only eligible individuals can cast votes or participate in decision-making. This reduces the risk of identity fraud, Sybil attacks, and manipulation of voting outcomes. Biometrics is able to protect decentralized governance systems against impersonation attempts, helping maintain the integrity and fairness of the governance system. Another benefit of biometrics for DAOs is that it can simplify access to governance functions and activities. Participants can securely access their governance accounts and perform actions such as voting, proposal submissions, or participation in discussions with a quick biometric scan. This user-friendly approach encourages greater engagement and participation in the decentralized governance process. To sum up, by leveraging biometric techniques, decentralized governance systems can enhance the security, trust, and efficiency of decision-making processes. Yield farming and staking Yield farming and staking are two popular concepts within the DeFi ecosystem that allow individuals to earn passive income by participating in various blockchain-based protocols. Yield farming, also known as liquidity mining, involves providing liquidity to DEXs or lending platforms. Users contribute their digital assets to liquidity pools, which are used to facilitate trading or lending activities. In return for providing liquidity, users are rewarded with additional tokens or fees generated by the protocol. These rewards can be in the form of the platform’s native tokens or other tokens associated with the protocol. Yield farming typically involves interacting with DApps that run on blockchain networks. Users can stake their tokens into specific liquidity pools or lending markets, where their assets are used to facilitate transactions or generate interest for borrowers. The more assets a user contributes and the longer they remain staked, the higher their potential yield or reward. Staking, on the other hand, involves holding and locking up a certain amount of tokens in a cryptocurrency network to support its operations. By staking tokens, users actively participate in the network’s consensus mechanism, helping to validate transactions and secure the blockchain. In return for their contribution, stakers are rewarded with additional tokens or fees generated by the network. Staking rewards vary depending on the specific blockchain network and its token economics. Some networks offer a fixed percentage return on staked tokens, while others utilize more complex mechanisms, such as inflationary rewards or variable rewards based on network activity. Staking can also provide governance rights, allowing token holders to participate in the decision-making process of the network by voting on proposals or protocol upgrades. Yield farming and staking platforms often face the risk of Sybil attacks, where malicious actors create multiple fake accounts to manipulate rewards or governance processes. Biometrics helps prevent fraud by ensuring that only authorized individuals can participate in these activities. Since biometric features are unique to each individual, it becomes extremely difficult for malicious actors to create fake accounts or manipulate the platform for personal gain and rewards. This enhances the overall security and integrity of the yield farming and staking ecosystem. By limiting each individual to a single account through biometric verification, the platform aims to ensure that the staking rewards are distributed accurately and fairly. It helps prevent users from creating multiple accounts to unfairly increase their chances of receiving rewards or manipulating the staking process. Additionally, having one account per person through biometric verification reduces the possibility of duplicate rewards. With multiple accounts, users could potentially stake their tokens across different accounts to earn rewards multiple times. Limiting users to a single account mitigates this issue and promotes a more equitable distribution of rewards among stakers. Also, biometrics provides a scalable solution for yield farming and staking platforms as they grow and attract a larger user base. Biometric traits can be efficiently verified and authenticated, even as the user count increases. This scalability enables platforms to accommodate a growing number of users without compromising security or user experience. It is crucial for yield farming and staking platforms to implement robust security measures, protect user privacy, and comply with relevant regulations when utilizing biometrics. This ensures that the benefits of biometrics are effectively harnessed while maintaining a secure, trusted, and user-friendly environment for yield farming and staking activities. Decentralized insurance Decentralized insurance protocols are an emerging concept within the DeFi universe. It aims to revolutionize the traditional insurance industry by leveraging decentralized tech to create transparent, efficient, and community-driven insurance solutions (Feng, 2023; Jha, 2021). Traditional insurance operates through centralized institutions that act as intermediaries between policyholders and insurers. These institutions often have significant control over policy terms, claim assessments, and premium pricing. In contrast, decentralized insurance aims to eliminate the need for intermediaries and empower individuals to directly participate in the insurance process. Decentralized insurance protocols are built on blockchains, enabling the creation of transparent and auditable systems. Smart contracts play a crucial role in automating various insurance processes, including policy issuance, premium payments, and claim settlements. In DeFi, policyholders can view and verify the terms of their insurance policies on the blockchain, ensuring that there is no ambiguity or hidden clauses. Additionally, claim settlements can be executed automatically based on predefined conditions coded in smart contracts, reducing the potential for delays or disputes. Decentralized insurance also has the potential to provide coverage for risks that are traditionally underserved or excluded by traditional insurance providers. By removing centralized decision-making processes, decentralized insurance protocols can offer more flexible and customized coverage options. This inclusivity opens up opportunities for individuals and businesses that may have difficulty obtaining coverage through traditional channels. Moreover, decentralized insurance protocols often leverage the power of community consensus and governance. Participants in the protocol hold governance tokens that allow them to vote on important decisions, such as risk assessment methodologies, premium pricing, and claim dispute resolutions. This community-driven governance model promotes a sense of ownership and collective decision-making, aligning the interests of policyholders and ensuring the fairness and sustainability of the insurance system. While implemented in decentralized issuance protocols, biometrics offers several specific advantages on top of the common ones applied to DeFi platforms as a whole. Thus, it can simplify and expedite claims processing in decentralized insurance systems. Policyholders can securely authenticate themselves using biometric scans, eliminating the need for complex paperwork or manual verification processes. This streamlines the claims workflow, reduces administrative overhead, and speeds up the reimbursement or settlement process for policyholders. Biometric data can provide valuable insights for underwriting and risk assessment in decentralized insurance. By analyzing biometric information, insurers can gain a better understanding of policyholders’ health, lifestyle, or behavior patterns. This enables more accurate risk assessment, personalized premium pricing, and the potential for customized insurance products tailored to individuals’ specific needs. And last but not least, biometric authentication enhances the overall customer experience in decentralized insurance. Policyholders can easily access their insurance accounts, submit claims, or engage in policy management activities with a simple biometric scan. This user-friendly approach reduces friction, improves convenience, and increases customer satisfaction. Overall, biometrics simplifies the verification process for insurance claims in decentralized systems. Biometric traits can serve as a reliable and tamper-resistant means of verifying policyholders’ identities and authenticating claims. This reduces the manual effort and time required for claims verification, leading to more efficient and accurate claim processing. Decentralized derivatives and options In a nutshell, derivatives are financial contracts that derive their value from an underlying asset, such as cryptocurrencies, commodities, or traditional financial instruments. Options are a type of derivative that gives the holder the right, but not the obligation, to buy or sell the underlying asset at a predetermined price within a specific timeframe. Decentralized derivatives and options are innovative financial instruments within the DeFi landscape. They enable participants to engage in derivative trading, including option contracts, without the need for traditional intermediaries or centralized exchanges. They utilize the blockchain to enable peer-to-peer trading and settlement of these instruments. By leveraging smart contracts, the terms and conditions of the derivatives contracts are programmatically executed, removing the need for intermediaries to oversee the contract execution and settlement process. The key benefit of decentralized derivatives and options is increased accessibility. Traditional derivatives markets are often restricted to institutional investors or accredited individuals due to regulatory requirements and high entry barriers. Decentralized derivatives protocols, however, are generally open to anyone with an internet connection and a compatible digital wallet, democratizing access to these financial instruments. Decentralized derivatives platforms also offer increased transparency and security. Trading activities, contract terms, and settlement processes are recorded on the blockchain, providing a verifiable and auditable record of transactions. Furthermore, decentralized derivatives and options protocols often integrate liquidity pools, allowing participants to trade derivatives directly with other users in a peer-to-peer manner. This eliminates the need for a centralized order book and enhances liquidity, enabling users to find counterparties for their trades more easily. Biometrics adds an extra layer of security to decentralized derivatives and options trading platforms. By requiring biometric verification, it becomes significantly more challenging for unauthorized individuals to access or manipulate users’ trading positions or funds. This helps protect users’ assets and prevents unauthorized transactions or malicious activities. Biometric authentication ensures that only authorized individuals can access decentralized derivatives and options trading platforms, helping prevent unauthorized access and reducing the risk of account breaches or funds being compromised. By allowing only one account per person, the platform promotes fairness and prevents individuals from creating multiple accounts to gain an unfair advantage. This helps maintain a level playing field and ensures that everyone has an equal opportunity to participate and benefit from the platform’s offerings. Apart from creating a seamless user experience, the implementation of biometric verification into decentralized derivatives and options trading platforms significantly enhances the trust and confidence of traders. When users have an assurance that their accounts are well-protected, they are more inclined to actively participate in trading activities and explore the various offerings of the platform. This heightened trust not only leads to increased user adoption but also contributes to the overall growth and success of the platform. Decentralized crowdfunding and ICO Decentralized crowdfunding, often referred to as decentralized fundraising or token sales, leverages blockchain to enable direct peer-to-peer fundraising. Projects or individuals looking to raise funds create a token that represents their project or venture and offer it to the public through a crowdfunding campaign. Interested participants can contribute funds, typically in the form of cryptocurrencies, in exchange for the newly created tokens. The main advantage of decentralized crowdfunding is the removal of intermediaries, allowing projects to directly engage with their supporters and receive funding without the need for a centralized platform. Initial Coin Offerings (ICOs) are a specific type of decentralized crowdfunding where the tokens offered represent a digital asset or utility within a project’s ecosystem. ICOs gained significant popularity during the cryptocurrency boom in 2017, as they provided a new way for blockchain-based projects to raise funds. Participants in ICOs typically receive tokens that can be used within the project’s ecosystem or have the potential for future value appreciation. Decentralized crowdfunding and ICOs provide a global reach, allowing projects to attract investors from around the world and tap into a larger pool of potential supporters. The process is typically more accessible, enabling smaller investors to participate and contribute to projects they believe in. Additionally, decentralized crowdfunding can foster community engagement and incentivization by involving token holders in project governance or offering exclusive benefits to early supporters. Biometric verification offers several benefits for decentralized crowdfunding and ICO platforms, enhancing their security, trust, and efficiency. With it, unauthorized access to users’ funds is mitigated, protecting their contributions and investments. This reinforces trust and transparency among participants, promoting confidence in the platform and the projects being funded. Biometric verification also prevents duplicate contributions and identity fraud. It makes it difficult for individuals to create multiple accounts or impersonate others, ensuring fairness and maintaining the integrity of funding outcomes. Additionally, biometrics aids in complying with regulatory requirements, such as investor identification and anti-money laundering procedures, reducing legal risks for the platform. The contribution process becomes more efficient and streamlined with biometrics. Contributors can securely verify their identities through a quick biometric scan, eliminating manual procedures and paperwork. This simplifies the process, reduces friction, and enhances the user experience. Privacy concerns are addressed by implementing privacy-preserving measures, such as encryption or decentralized storage of biometric data. This ensures user privacy while maintaining the security of the authentication and verification processes. Decentralized prediction markets Decentralized prediction markets are innovative platforms that leverage blockchain to enable individuals to make predictions on a wide range of events and outcomes. These markets operate without a central authority, allowing participants to engage in peer-to-peer prediction trading, creating a decentralized ecosystem for forecasting (Peterson & Krug, 2015; Atanasov et al., 2017) At the core of decentralized prediction markets is the concept of smart contracts that define the rules and conditions of the prediction market, including the event or outcome being predicted, the duration of the market, and the payout structure. They also ensure the transparency and integrity of the market by automating the process of settling bets and distributing rewards. Participants in decentralized prediction markets can place bets by purchasing prediction tokens or shares associated with a particular outcome. The price of these tokens fluctuates based on the perceived likelihood of the outcome. For example, if the market predicts a 70% chance of an event occurring, the tokens associated with that outcome would be priced higher than those associated with a lower probability. The collective intelligence of participants drives the accuracy of predictions in these markets. By leveraging the wisdom of the crowd, decentralized prediction markets have the potential to provide more accurate forecasts compared to traditional forecasting methods. Participants can use their expertise and insights to make informed predictions, while also considering the predictions of others. Decentralized prediction markets can cover a wide range of topics, including politics, sports, finance, and even climate change. By allowing individuals to trade on the outcomes of events, these markets provide valuable insights into future events and create a mechanism for crowd-sourced forecasting. The essential merit of decentralized prediction markets is their ability to mitigate manipulation and tampering. Since the markets are built on blockchain, all transactions and predictions are recorded immutably on the distributed ledger, making it nearly impossible to alter or manipulate the results. Additionally, the decentralized nature of these markets reduces the risk of a single point of failure or control, enhancing their reliability and trustworthiness. With biometrics, decentralized prediction markets can enhance the security, trust, and accuracy of market outcomes. Since in decentralized prediction markets, reputation and credibility are crucial, by using biometrics to ensure uniqueness, these platforms can establish a reputation system that associates the individual’s predictions and actions with their verified identity. This can help build trust among participants and provide a reliable measure of the user’s track record and expertise. Biometric verification helps prevent insider trading in decentralized prediction markets. By tying specific biometric traits to user identities, it becomes easier to trace and verify the actions of individual participants. This enhances transparency and accountability, reducing the likelihood of market manipulation or unfair advantage. Privacy protection is also prioritized in biometric verification for decentralized prediction markets. Crypto-biometrics can safeguard sensitive user information and address privacy concerns. Adding an additional layer of accountability to decentralized prediction markets, biometric verification can deter fraudulent activities and promote responsible participation in the market. Since each user’s actions and predictions are tied to their verified identity, it becomes easier to hold individuals accountable for their behavior. On top of that, biometric authentication simplifies the participation process in decentralized prediction markets. Participants can securely verify their identities and engage in market activities with a quick biometric scan, streamlining the participation process, reducing friction, and enhancing the overall user experience. Decentralized oracles Decentralized oracles are an integral component of blockchain ecosystems that provide external data to smart contracts and DApps. Basically, they serve as bridges between the on-chain world of blockchain networks and the off-chain world of real-world data (Liu, et al., 2021; Caldarelli & Ellul, 2021). In blockchain systems, smart contracts are self-executing agreements that rely on predefined conditions. However, these contracts lack direct access to real-time data such as stock prices, weather conditions, sports scores, or other information from external sources. This is where decentralized oracles come into play. Decentralized oracles act as intermediaries between the blockchain and external data sources, ensuring that accurate and reliable information is fed into smart contracts. They fetch data from multiple sources, aggregate it, and deliver it to the blockchain for use by smart contracts and DApps. There are different types of decentralized oracles, each designed to serve specific purposes. First, there are simple oracles that provide basic data inputs to the blockchain, such as timestamps or random number generation. They are straightforward and don’t require complex data verification processes. Then, there are hardware oracles that focus on providing data from physical devices or IoT (Internet of Things) devices. They ensure that information from sensors, devices, or external hardware is securely transmitted to the blockchain. Software oracles extract data from external software systems, APIs (Application Programming Interfaces), or web services and are commonly used to fetch information like exchange rates, weather forecasts, or sports scores. And last but not least, consensus-based oracles rely on a decentralized network of data providers or validators to obtain and validate external data. They use consensus algorithms to ensure data accuracy and mitigate the risks of single points of failure or manipulation. Biometric-based identity verification enhances the security of data feeds by ensuring that only authorized individuals can submit data to the oracle. This helps prevent unauthorized manipulation or tampering of data, ensuring the integrity and accuracy of the information provided to smart contracts. It also enhances the accountability of data providers. By linking biometric data to the identities of data contributors, it becomes easier to trace and verify the actions of individual providers. This promotes responsibility and discourages malicious behavior, ensuring that data providers are accountable for the accuracy and reliability of the data they submit. Moreover, biometric solutions streamline the data validation process in decentralized oracles. Instead of relying on complex manual verification procedures or third-party intermediaries, biometrics enables quick and reliable validation of data sources. This improves the efficiency of the oracle, reduces delays in data verification, and enhances the overall performance of smart contracts relying on the oracle’s data. Mainly, biometric approaches reinforce the trustworthiness and transparency of decentralized oracles. By tying specific biometric traits to the identities of data providers, it becomes easier to verify and validate the authenticity of the data being fed into the oracle. This enhances trust among users of the oracle and promotes transparency in the data aggregation process. Decentralized identity Decentralized identity (DID) refers to the concept of individuals having control over their own digital identities without relying on central authorities or intermediaries (Avellaneda et al., 2019; Alizadeh et al., 2022; Dib & Toumi, 2020; Fdhila et al., 2021) It is known that traditional identity systems involve centralized databases or institutions that store and control individuals’ personal information. This can lead to privacy and security concerns, as well as a lack of control over one’s own identity. The decentralized identity aims to address these issues by providing a user-centric model where individuals have sovereignty over their digital identities. In decentralized identity systems, individuals create unique identifiers, known as DIDs, which are stored on a blockchain or a distributed ledger. These DIDs serve as digital representations of their identities and can be associated with various attributes, such as personal information, credentials, or reputation scores. Importantly, individuals retain control over their DIDs and the associated data. The main feature of decentralized identity is the ability to selectively share personal information (PII) with different entities while maintaining privacy. Individuals can choose to disclose specific attributes or credentials without revealing their entire identity or data. This granular control over data sharing helps protect privacy and prevents unnecessary exposure of sensitive information. Biometric-based identity verification can help resolve several issues related to DID systems. First, it provides a universal and standardized method for identity verification across different platforms and applications. By utilizing biometric traits, decentralized identity systems can establish a common mechanism that transcends individual platforms and enables interoperability. Biometric standards, such as those for fingerprint or facial recognition, are widely recognized and implemented by various technologies, facilitating seamless integration and interoperability within the DID ecosystem. Second, biometrics enhances the reliability of identity verification in DID systems. Biometric traits are unique to each individual and difficult to forge, making them highly reliable for confirming the authenticity of an individual’s identity. By utilizing biometric-based verification, decentralized identity systems can establish a robust and trusted verification mechanism, ensuring that identities are accurately verified and reducing the risk of fraudulent or impersonated credentials. Biometric traits, once enrolled, remain relatively constant over time and are difficult to change. This immutability of biometric data helps address the challenges associated with the revocation and updating of credentials in DID systems. When a user needs to update their credentials or revoke access, the underlying biometric data associated with their identity remains unchanged, allowing for seamless transitions without compromising the security or integrity of the identity system. Biometrics offers the potential for granular revocation of credentials in DID systems. Since biometric traits are unique to each individual, revoking access for a specific biometric identifier can be selectively done without affecting other credentials associated with the user. This allows for more fine-grained control over revocation and minimizes disruption to the user’s overall identity and access privileges. Additionally, biometric-based techniques enable real-time updates of credentials in decentralized identity systems. For example, if a user’s biometric data changes due to aging or a physical injury, the verification system can be updated accordingly to accommodate the new biometric traits. This ensures that the user’s identity remains valid and up to date, without requiring extensive manual updates or reissuing of credentials. Moreover, biometric-based authentication simplifies the management of credentials in decentralized identity systems. Traditional password-based systems often require frequent updates, changes, and revocations, which can be cumbersome for both users and service providers. By replacing passwords with biometric authentication, the need for regular credential updates is significantly reduced, streamlining the management process and reducing administrative overhead. To sum up, by leveraging biometrics, decentralized identity systems can establish standardized interoperability, address the challenges of revocation and updating of credentials, and provide a robust and reliable identity verification mechanism. Decentralized invoices Decentralized invoices refer to a system or process that leverages decentralized technologies to create, manage, and settle invoices in a trustless and transparent manner. Utilizing the principles of decentralization, these systems aim to streamline and enhance the efficiency of invoicing processes while maintaining data integrity and security. In traditional invoicing systems, invoices are typically generated, managed, and validated by centralized entities, such as companies or financial institutions. This centralized approach can lead to inefficiencies, delays, and potential disputes due to manual processes, data silos, and the need for intermediaries. Decentralized invoice systems, on the other hand, enable the direct creation and issuance of invoices on the blockchain by relevant parties. These invoices include all necessary details and are transparent, immutable, and accessible to authorized parties. This reduces the risk of fraudulent or tampered invoices. And smart contracts facilitate automatic payment calculations, due date reminders, and trigger payments based on predefined conditions, reducing manual intervention and minimizing human error. Transparency and immutability of blockchain records in decentralized invoice systems create an auditable trail for invoice-related activities. This aids in streamlining dispute resolution by providing an accurate and verifiable record of invoice issuance, revisions, and payments. By eliminating intermediaries and optimizing manual processes, decentralized invoice systems reduce administrative costs and save time for all parties involved. Automation and transparency offered by smart contracts and blockchain enhance efficiency and accelerate the invoicing lifecycle. Furthermore, decentralized invoice systems can ensure transparency while selectively disclosing information on a need-to-know basis. Confidential information can be encrypted and shared only with authorized parties, ensuring data security and privacy compliance. Biometrics provides a high level of user identity verification for decentralized invoices. Leveraging biometric traits such as fingerprints, irises or faces, users can securely access their invoice accounts or authorize transactions. This eliminates the risk of unauthorized access to invoice data or fraudulent activities, enhancing the overall security of the decentralized invoicing system. Biometric authentication offers a seamless and user-friendly experience for decentralized invoices. Users can easily authenticate themselves using their biometric traits, eliminating the need to remember and enter complex passwords or PINs. This streamlines the login process, reduces friction, and enhances the overall user experience, leading to increased user adoption and satisfaction. In addition, biometric authentication eliminates the reliance on passwords, reducing the risk of password-related issues in decentralized invoicing systems. Users no longer need to create and remember passwords, resulting in a more secure and convenient authentication process. Implemented in invoice systems biometric verification provides non-repudiation and accountability in them. Each interaction or transaction can be linked to a specific biometric identifier, ensuring that the actions of users are uniquely tied to their identity. This strengthens the auditability of invoice-related activities and establishes a clear chain of accountability, reducing the risk of disputes or fraudulent claims. On top of that, biometrics can be combined with other factors, such as passwords or tokens, to create multi-factor authentication (MFA) in decentralized invoicing systems. This further enhances the security of user accounts by requiring multiple independent forms of authentication. The combination of biometrics with other factors adds an extra layer of protection and reduces the likelihood of unauthorized access or fraudulent activities. Also, biometric verification can assist in meeting regulatory requirements related to data security and privacy. In some jurisdictions, certain industries, or for specific types of transactions, the use of strong verification measures, including biometrics, may be mandated. By implementing biometrics in decentralized invoicing systems, businesses can ensure compliance with applicable regulations and demonstrate their commitment to protecting sensitive data. Basically, biometrics provides a robust and reliable verification mechanism that aligns with the decentralized nature of the invoicing process, ensuring that only unique authorized users can access and interact with their invoice accounts securely. Automated market-making Automated market-making (AMM) is a mechanism used in DEXs to facilitate the trading of digital assets in a decentralized and automated manner. AMM relies on algorithms and smart contracts to create and manage liquidity pools, determine asset prices, and enable trading without relying on traditional order books or intermediaries (Mohan, 2022; Park, 2022). In traditional centralized exchanges, the order book model matches buy and sell orders based on predefined prices and quantities. However, in decentralized exchanges, AMM replaces the order book with liquidity pools that hold reserves of different tokens. These pools enable users to trade assets directly against the reserves without needing a counterparty. The core concept of AMM is based on the constant product formula, often referred to as the “xy=k” formula. It states that the product of the reserve balances of two tokens in a liquidity pool remains constant. For example, if Token A and Token B are in a pool with reserves of 100 and 200 respectively, the product (xy) would be 20,000. As trades occur, the reserve balances adjust while keeping the product constant. When a user wants to trade a specific token, they interact with the liquidity pool by swapping one token for another. The algorithm calculates the number of tokens to be exchanged based on the pool’s current reserves and the constant product formula. This means that the price of a token in relation to another token is determined by the ratio of their reserves in the pool. As trades occur, the liquidity pool rebalances itself to reflect the new reserve ratios. If a trade increases the supply of Token A, it will decrease the supply of Token B to maintain the constant product. This mechanism ensures that liquidity is always available for trading, and the price of assets adjusts based on supply and demand. AMM systems often incentivize users to provide liquidity to the pools by offering them fees generated from trades. These fees are distributed proportionally to liquidity providers based on their contribution to the pool. This model encourages users to contribute to liquidity and ensures the continuous availability of trading pairs. Biometrics adds a level of user accountability to AMM systems. Each transaction or action can be tied to a specific biometric identifier, ensuring that users are uniquely identified and their activities are traceable. This strengthens the auditability of transactions and provides a clear chain of accountability, making it easier to identify any suspicious or fraudulent behavior. Another layer added by biometrics is an extra layer of protection as it reduces the risk of unauthorized access or fraudulent activities within the market-making platform. Biometric traits are unique to each individual and difficult to forge, making it significantly more challenging for malicious actors to impersonate someone’s identity or manipulate transactions. In addition, biometrics can help reduce operational costs associated with password management and user support, resulting in lower operational expenses and improved efficiency for the platform operators. Seamless cross-platform authentication in AMM ecosystems can also be facilitated. Users can authenticate themselves using their biometric traits across multiple platforms and services within the ecosystem, eliminating the need for separate login credentials for each platform. This experience simplifies user interactions, promotes interoperability, and encourages greater participation in the ecosystem as a whole. Needless to say, biometrics provides a future-proof verification method. As technology advances, traditional methods may become outdated or vulnerable to new threats. Biometrics, on the other hand, offers a long-term solution that can adapt to evolving security requirements. This future-proof nature ensures that the AMM platform remains secure and resilient against emerging identity risks. Summing up, by leveraging biometrics, AMMs can enhance security, streamline the user experience, prevent fraud, and build trust among users. Tokenization of assets Tokenization is the process of representing real-world assets, such as real estate, artworks, commodities, or financial instruments, as digital tokens on a blockchain (Freni et al., 2020; Gupta et al., 2020; Lotti, 2019). These assets can then be bought, sold, and traded on various decentralized platforms, providing increased liquidity, fractional ownership, and new investment opportunities. Biometrics offers a robust and reliable method of user verification for tokenized assets. Biometric traits are unique, making it significantly more difficult for unauthorized users to impersonate someone’s identity. By leveraging biometrics, tokenized asset platforms can ensure that only legitimate owners or authorized users have control over their assets, reducing the risk of unauthorized transactions. Furthermore, biometric authentication streamlines the process of transferring tokenized assets. This simplifies reduces the risk of human error or key theft, and improves the overall user experience when managing tokenized assets. Biometrics combined with blockchain is able to create an immutable audit trail for tokenized assets. Every transaction or interaction involving the assets can be linked to a specific biometric identifier, creating a transparent and traceable record of ownership and asset movements. This enhances accountability, simplifies auditing processes, and provides a clear chain of custody for tokenized assets. Accessibility, adoption, and inclusion in the tokenization of assets can also be streamlined. Biometric traits are inherently tied to individuals, removing the need for complex passwords or cryptographic keys that may be challenging for some users. Biometrics makes it easier for a broader range of individuals to participate in the crypto ecosystem, including those who may have limited technical knowledge or physical disabilities. The aforementioned advantages contribute to a more secure, efficient, and inclusive ecosystem for managing and transferring tokenized assets, unlocking new opportunities for asset ownership and investment. Decentralized cross-border payments Decentralized cross-border payments refer to a payment system that operates in a decentralized manner and leverages blockchain to facilitate secure and efficient transactions between parties located in different countries. These payment systems aim to overcome the challenges and limitations of traditional cross-border payment methods, such as slow processing times, high fees, and intermediaries. In decentralized cross-border payment systems, transactions are conducted directly between the involved parties without the need for intermediaries like banks or payment processors. Instead, the transactions are validated and recorded on a distributed ledger, which is maintained by a network of participants. This decentralized infrastructure ensures transparency, security, and immutability of payment records. Biometrics can aid in improving several issues in decentralized cross-border payments, including regulatory considerations, interoperability, liquidity management, and compliance with AML and KYC regulations. Many jurisdictions have regulations in place to prevent illicit activities, ensure customer protection, and promote compliance with AML and KYC standards. Biometrics provides a robust method for verifying the identity of individuals involved in cross-border transactions, helping decentralized payment systems adhere to regulatory guidelines. Furthermore, biometrics can facilitate interoperability among different blockchain networks. Such methods can be standardized across various platforms, enabling seamless integration and communication between different networks. This interoperability allows participants to transact across different blockchains, improving liquidity and expanding the reach of decentralized cross-border payments. Biometrics can assist in liquidity management since with it participants can securely and quickly access their funds. This reduces liquidity constraints by enabling timely access to assets, improving the efficiency and liquidity of cross-border payment transactions. As for compliance requirements for AML and KYC regulations in decentralized cross-border payments, biometric traits provide a strong means of verifying the identity of individuals, ensuring compliance with regulatory obligations. By linking biometric data with user identities, decentralized payment systems can establish robust KYC procedures and perform enhanced due diligence to prevent money laundering and illicit financial activities. Needless to say, biometrics fosters trust and confidence among participants in decentralized cross-border payments, reducing concerns about fraudulent activities and unauthorized access. This increased trust and confidence encourage more individuals and businesses to participate in decentralized cross-border payments, leading to a more robust and vibrant ecosystem. Decentralized savings and retirement plans Decentralized savings and retirement plans are financial solutions built on blockchain networks that enable individuals to save, invest, and plan for their retirement in a decentralized and self-sovereign manner. Traditional savings and retirement plans often rely on centralized financial institutions, such as banks, investment firms, or pension funds, to manage and administer funds. However, decentralized savings and retirement plans aim to provide individuals with more control, transparency, and potentially higher returns on their savings through the use of decentralized technologies. Biometrics facilitates efficient and secure account management in decentralized savings and retirement plans. Participants can securely access their accounts, view their balances, track their investments, and perform transactions by using their biometric traits. This eliminates the need for cumbersome verification procedures and enhances the overall user experience, making it easier and more efficient to manage savings and retirement funds. Again, biometrics offers convenient and user-friendly access DeFi platforms. Participants can authenticate themselves by using their biometric traits. It improves accessibility for elderly or disabled individuals participating in decentralized savings and retirement plans. Biometric traits, such as fingerprints or facial recognition, are often more accessible and user-friendly for individuals with limited dexterity or visual impairments. This ensures that a wider range of individuals can actively engage in managing their savings and retirement funds. Moreover, due to biometrics’ implementation, DeFi platforms can seamlessly integrate with other financial services and applications. Users can use their biometrics across different platforms and services, ensuring a consistent and unified experience. This integration enhances interoperability and makes it easier to access a range of financial products and services, such as loans, insurance, or investment opportunities, within the decentralized ecosystem. In summary, biometrics brings enhanced security, protection against identity theft, convenience, improved trust and confidence, efficient account management, seamless integration with financial services, and personalized services to decentralized savings and retirement plans. These benefits contribute to a more secure, user-friendly, and personalized approach to managing savings and planning for retirement. Decentralized fundraising for social impact Decentralized fundraising for social goods leverages the principles of decentralization, smart contracts, and community participation to enable individuals and organizations to support social initiatives and make a positive impact. Such a mechanism has the potential to revolutionize philanthropy and social initiatives by increasing transparency, inclusivity, and efficiency. It allows individuals and organizations to directly support causes they care about and fosters community collaboration. The good thing is, decentralized fundraising platforms provide the opportunity to reach a global audience, allowing individuals from anywhere in the world to contribute to social impact projects. Cryptocurrencies and blockchain-based systems can help address financial inclusion barriers by reducing transaction costs and enabling micropayments, making it easier for individuals with limited access to traditional financial systems to participate. Biometric verification fosters trust and transparency in decentralized fundraising for social impact. Philanthropes and donors can have increased confidence that their contributions are going to legitimate causes and that the recipients are genuinely in need. Biometrics provides a strong and reliable means of verifying the identities of beneficiaries, ensuring that funds are directed to the right individuals or projects. It also enhances accountability in decentralized fundraising as by linking biometric traits to individual identities, it becomes easier to track and verify participation and contributions. This ensures that funds are allocated and used transparently, reducing the risk of fraud or mismanagement. Biometrics adds a layer of trust and confidence, making people more willing to contribute to social impact initiatives. On top of that, such a type of authentication facilitates efficient and timely fund disbursement in decentralized fundraising for social impact. By securely verifying the biometric traits of beneficiaries, funds can be disbursed directly to the intended recipients without the need for intermediaries or complex verification processes. This improves the speed and efficiency of delivering funds to those in need, ensuring that social impact initiatives can be implemented more effectively. Mainly, biometrics brings benefits such as enhanced accountability, reduced fraud and identity theft, trust and transparency, simplified user experience, privacy protection, inclusion and accessibility, and efficient fund disbursement to decentralized fundraising for social impact. Part V. Challenges of Sybil-resistant biometrics for DeFi While biometric verification offers promising solutions to combat Sybil attacks in DeFi, several challenges exist that must be carefully considered to ensure its effective implementation. This part will discuss these challenges in more detail. Sybil-resistant biometrics in DeFi is accompanied by several challenges that revolve around the diversity of biometric traits, security and vulnerabilities, user acceptance and privacy concerns, regulatory and legal compliance, infrastructure requirements, and usability. One of the primary challenges lies in ensuring the security of biometric data. Biometric information, being inherently unique and personally identifiable, is highly sensitive. Safeguarding biometric data from unauthorized access, tampering, or theft is essential to maintain user trust and prevent potential attacks. Humanode is implementing advanced cryptography and robust anti-spoofing measures, such as liveness detection, enhancing the reliability of biometric identity verification in DeFi. Deploying Sybil-resistant biometrics in DeFi platforms also requires compliance with various privacy and data protection regulations. Biometric data is subject to stringent regulatory frameworks that govern its collection, storage, and usage. Platforms must ensure appropriate consent mechanisms, secure data storage practices, and compliance with relevant legal requirements to protect user privacy and mitigate legal risks. Complying with regulatory obligations, such as the GDPR’s principles of data minimization, purpose limitation, and accountability, necessitates robust data governance practices and ongoing monitoring of compliance measures. The adoption of biometrics in DeFi platforms is another critical concern in deploying biometrics. Mainly, adoption relies on user acceptance and confidence in the technology. However, individuals may have concerns regarding the privacy and security of their biometric information. It is imperative to address these concerns through transparent communication, educating users about the robust privacy measures and encryption protocols implemented in biometric systems, and providing clear consent mechanisms for data collection and usage. Respecting user privacy and ensuring compliance with relevant privacy regulations, are paramount to fostering user trust and widespread acceptance of biometric-based systems. Usability and user experience also play a vital role in the successful adoption of biometric methods in DeFi. If the enrollment process is user-friendly, ensuring ease of capturing biometric data while maintaining accuracy and reliability, the users are most likely to be satisfied. Continual user testing, feedback collection, and iterative improvements are necessary to enhance the usability and user experience of biometric-based Sybil-resistant systems in DeFi. Continual user testing, feedback collection, and iterative improvements are necessary to enhance the usability and user experience of biometric-based DeFi systems. Also, DeFi platforms often experience rapid growth in user base and transaction volume. Scalability becomes a critical challenge for biometric systems, as they need to handle a large number of concurrent verification requests efficiently. Ensuring that the biometric infrastructure can scale seamlessly to accommodate the growing user demands while maintaining high performance and response times is essential. Addressing these challenges requires a multidimensional approach involving advancements in biometric technology, robust system architecture, user education, privacy measures, and collaboration with regulatory bodies. Overcoming these challenges is crucial to harness the full potential of Sybil-resistant biometrics in defending against identity attacks and promoting a secure and trustworthy DeFi ecosystem. Discussion The rapid growth of DeFi platforms apart from numerous benefits has introduced various security challenges, with identity attacks being one of the significant concerns. In this paper, we explored a novel approach to mitigate Sybil attacks in DeFi through biometric-based verification mechanisms. The research analyzed the potential advantages of integrating biometrics into the existing identity verification schemes of DeFi frameworks. By incorporating biometric verification at various stages of user onboarding, such as account creation, asset transfers, or interaction with smart contracts, we can significantly enhance the security posture of DeFi platforms. The main thing is, biometric verification mechanisms can prevent Sybil attacks by establishing a link between an individual and a single account, limiting the ability of attackers to manipulate the network through multiple identities. This strengthens the integrity of DeFi platforms, ensuring that genuine users have more control and influence over the network. However, it is important to acknowledge the potential limitations and challenges associated with the implementation of biometric-based Sybil resistance in DeFi. Privacy concerns and the storage of sensitive biometric data pose significant ethical and security challenges. Safeguarding biometric information is of utmost importance to prevent potential misuse or unauthorized access. Robust encryption and crypto-biometric practices, as one proposed by the Humanode initiative, must be implemented to protect user privacy and prevent unauthorized access to biometric data. Another potential challenge is the scalability of biometric-based Sybil resistance solutions. As DeFi platforms continue to attract a larger user base, the computational resources required for biometric verification may increase significantly. Addressing scalability concerns and optimizing the performance of biometric algorithms will be crucial to ensure the seamless operation of DeFi platforms. Careful consideration must be given to privacy, security, accuracy, and scalability concerns during the implementation of biometric-based Sybil resistance solutions. Future research should focus on addressing these challenges to ensure the widespread adoption of this approach in DeFi platforms. Conclusion As explored in this paper, Sybil-resistant biometrics for DeFi has the potential to foster greater trust among DeFi platforms’ users, encourage broader adoption, and enable the realization of the full potential of decentralized finance. It holds great promise in mitigating identity attacks and enhancing security within the ecosystem. Biometric-based Sybil resistance mechanism offers a robust solution to the challenges posed by fraudulent identities, impersonation, and malicious activities in DeFi protocols. By leveraging biometric verification, DeFi platforms can introduce an additional layer of security that is difficult to replicate or bypass. The uniqueness and individuality of biometric traits make it significantly harder for attackers to create multiple fake accounts or manipulate identities for malicious purposes. Looking ahead, the future of Sybil-resistant biometrics in DeFi relies on user adoption, advancements in biometric technology, standardization of protocols, and collaboration among industry participants. Continued research and development efforts are necessary to refine and optimize biometric verification methods, making them more reliable, secure, and accessible for widespread adoption in the DeFi space. References Abdulhakeem, S. A., & Hu, Q. (2021). Powered by Blockchain technology, DeFi (Decentralized Finance) strives to increase financial inclusion of the unbanked by reshaping the world financial system. Modern Economy, 12(01), 1. Al-Qurishi M., M. Al-Rakhami, A. Alamri, M. Alrubaian, S. M. M. Rahman, and M. S. Hossain (2017) Sybil defense techniques in online social networks: A survey,” IEEE Access, vol. 5, pp. 1200–1219. Amler, H., Eckey, L., Faust, S., Kaiser, M., Sandner, P., & Schlosser, B. (2021, September). Defi-ning defi: Challenges & pathway. In 2021 3rd Conference on Blockchain Research & Applications for Innovative Networks and Services (BRAINS) (pp. 181–184). IEEE. Aramonte, Sirio, Wenqian Huang, and Andreas Schrimpf (2021) DeFi Risks and the Decentralisation Illusion. Basel: Bank for International Settlements (BIS), pp. 1–36. Atzei, Nicola & Bartoletti, Massimo & Cimoli, Tiziana. (2017). A Survey of Attacks on Ethereum Smart Contracts (SoK). 164–186. 10.1007/978–3–662–54455–6_8. Ayaz, F.; Sheng, Z.; Tian, D.; Liang, G.Y.; Leung, V. A Voting Blockchain based Message Dissemination in Vehicular Ad-Hoc Networks (VANETs). In Proceedings of the ICC 2020–2020 IEEE International Conference on Communications (ICC), Dublin, Ireland, 7–11 June 2020; pp. 1–6. Azbeg, K.; Ouchetto, O.; Jai Andaloussi, S.; Fetjah, L. An Overview of Blockchain Consensus Algorithms: Comparison, Challenges and Future Directions. In Advances on Smart and Soft Computing; Springer: Berlin/Heidelberg, Germany, 2021; pp. 357–369. Atzori, M. (2015). Blockchain technology and decentralized governance: Is the state still necessary?. Available at SSRN 2709713. Bartoletti, Massimo, James Hsin-yu Chiang, and Alberto Lluch Lafuente (2021) Towards a Theory of Decentralized Finance. Paper persented at International Conference on Financial Cryptography and Data Security, Berlin/Heidelberg, Germany, March 1–5. Barbereau, T., Smethurst, R., Papageorgiou, O., Rieger, A., & Fridgen, G. (2022). Defi, not so decentralized: The measured distribution of voting rights. Bekemeier, Felix. (2021) Deceptive Assurance? A Conceptual View on Systemic Risk in Decentralized Finance (DeFi). Paper persented at 2021 4th International Conference on Blockchain Technology and Applications, Xi’an, China, December 17–19. Bhambhwani, S. M. (2022). Governing Decentralized Finance (Defi). Available at SSRN 4225775. Bolle, R. M., Connell, J. H., Pankanti, S., Ratha, N. K., & Senior, A. W. (2013). Guide to biometrics. Springer Science & Business Media. Buterin, V. (2014) A Next-Generation Smart Contract and Decentralized Application Platform. https://ethereum.org/669c9e2e2027310b6b3cdce6e1c52962/Ethereum_Whitepaper_-_Buterin_2014.pdf Calcaterra, Craig, and Wulf A. Kaal. (2021) Decentralized Finance (DeFi). Decentralization-Technology’s Impact On Organizational and Societal Structure. Berlin: Degruyter Publishers. Caldarelli, G., & Ellul, J. (2021). The blockchain oracle problem in decentralized finance — a multivocal approach. Applied Sciences, 11(16), 7572. Carter, N., & Jeng, L. (2021). DeFi protocol risks: The paradox of DeFi. Regtech, Suptech and Beyond: Innovation and Technology in Financial Services” RiskBooks–Forthcoming Q, 3. Caronni, G. (2000). Walking the web of trust. In Proceedings IEEE 9th International Workshops on Enabling Technologies: Infrastructure for Collaborative Enterprises (WET ICE 2000) (pp. 153–158). IEEE. Cao, Qiang & Sirivianos, Michael & Yang, Xiaowei & Pregueiro, Tiago. (2012). Aiding the detection of fake accounts in large scale social online services. 15–15. Chen, Y., & Bellavitis, C. (2020). Blockchain disruption and decentralized finance: The rise of decentralized business models. Journal of Business Venturing Insights, 13, e00151. Chohan, Usman W. (2021) Decentralized Finance (DeFi): An Emergent Alternative Financial Architecture. Islamabad: Critical Blockchain Research Initiative (CBRI). Choudhury B., P. Then, B. Issac, V. Raman, and M. Haldar (2018) A survey on biometrics and cancelable biometrics systems. International Journal of Image and Graphics, vol. 18. Cong, L. W., & He, Z. (2019). Blockchain disruption and smart contracts. The Review of Financial Studies, 32(5), 1754–1797. De Hert, P. (2005). Biometrics: legal issues and implications. Background Paper for the Institute of Prospective Technological Studies, DG JRC–Sevilla, European Commission. Down, M. P., & Sands, R. J. (2004). Biometrics: An overview of the technology, challenges and control considerations. Information Systems Control Journal, 4, 53–56. Douceur, J. R. (2002) The Sybil Attack. 2002. https://www.microsoft.com/en-us/research/wpcontent/uploads/2002/01/IPTPS2002.pdf, Ford, Bryan. (2020). Identity and Personhood in Digital Democracy: Evaluating Inclusion, Equality, Security, and Privacy in Pseudonym Parties and Other Proofs of Personhood. Ford B. and J. Strauss, (2008) An offline foundation for online accountable pseudonyms”, Proceedings of the 1st Workshop on Social Network Systems, pp. 31–36. van Flymen, D. Proof of Work (2020) In Learn Blockchain by Building One; Apress: Berkeley, CA, USA, pp. 39–53. Gent, E. (2023). A Cryptocurrency for the Masses or a Universal ID?: Worldcoin Aims to Scan all the World’s Eyeballs. IEEE Spectrum, 60(1), 42–57. Grassi, Laura, Davide Lanfranchi, Alessandro Faes, and Filippo Maria Renga (2022) Do we still need financial intermediation? The case of decentralized finance–DeFi. Qualitative Research in Accounting & Management 19: 323–47. Grech A. et al. (2022) Blockchain, Self-Sovereign Identity and Digital Credentials: Promise Versus Praxis in Education. Volume 4–2021 | https://doi.org/10.3389/fbloc.2021.616779 Green, Aaron, Christopher Cammilleri, John S. Erickson, Oshani Seneviratne, and Kristin P. Bennett (2022) DeFi Survival Analysis: Insights into Risks and User Behaviors. Troy: The Rensselaer Institute for Data Exploration and Applications, Rensselaer Polytechnic Institute, pp. 1–15. Ghaffari F. (2022) Identity and access management using distributed ledger technology: A survey. https://hal.science/hal-03315497/document Gudgeon, L., Perez, D., Harz, D., Livshits, B., & Gervais, A. (2020). The decentralized financial crisis. In 2020 crypto valley conference on blockchain technology (CVCBT) (pp. 1–15). IEEE. Harnad, S. (2000). Minds, machines and Turing: The indistinguishability of indistinguishables. Journal of Logic, Language, and Information, 9(4), 425–445. Harvey, C. R., Ramachandran, A., & Santoro, J. (2021). DeFi and the Future of Finance. John Wiley & Sons. Jain, A. K., & Kumar, A. (2010). Biometrics of next generation: An overview. Second generation biometrics, 12(1), 2–3. Jain, A. K., Ross, A., & Pankanti, S. (2006). Biometrics: a tool for information security. IEEE transactions on information forensics and security, 1(2), 125–143. Karantias, K., Kiayias, A., & Zindros, D. (2020). Proof-of-burn. In Financial Cryptography and Data Security: 24th International Conference, FC 2020, Kota Kinabalu, Malaysia, February 10–14, 2020 Revised Selected Papers 24 (pp. 523–540). Springer International Publishing. Kavazi D., V.Smirnov, S. Shilina, MD Li, R. Contreras, H. Gajera, D. Lavrenov (2021) Humanode whitepaper: You are [not] a bot. arXiv preprint arXiv:2111.13189 Kaur G. and C. K. Verma (2014) Comparative analysis of biometric modalities, International Journal of Advanced Research in Computer Science. Kemmoe, V. Y., Stone, W., Kim, J., Kim, D., & Son, J. (2020). Recent advances in smart contracts: A technical overview and state of the art. IEEE Access, 8, 117782–117801. Khare Rohit and Adam Rifkin (1997) Weaving a Web of Trust. World Wide Web Journal. Volume 2, Number 3, Pages 77–112. Lesaege, C., Ast, F., & George, W. (2019). Kleros Short Paper v1.0.7. https://kleros.io/static/whitepaper_en-8bd3a0480b45c39899787e17049ded26.pdf Li, W., Bu, J., Li, X., & Chen, X. (2022). Security analysis of DeFi: Vulnerabilities, attacks and advances. In 2022 IEEE International Conference on Blockchain (Blockchain) (pp. 488–493). IEEE. Liu, B., Szalachowski, P., & Zhou, J. (2021). A first look into defi oracles. In 2021 IEEE International Conference on Decentralized Applications and Infrastructures (DAPPS) (pp. 39–48). IEEE. Ma, X.; Ge, C.; Liu, Z. (2019 )Blockchain-Enabled Privacy-Preserving Internet of Vehicles: Decentralized and Reputation-Based Network Architecture; Springer: Berlin/Heidelberg, Germany; pp. 336–351. Maymounkov, P., & Mazieres, D. (2002). Kademlia: A peer-to-peer information system based on the xor metric. In International Workshop on Peer-to-Peer Systems (pp. 53–65). Berlin, Heidelberg: Springer Berlin Heidelberg. Maskey, S.R.; Badsha, S.; Sengupta, S.; Khalil, I. (2021) Reputation-Based Miner Node Selection in Blockchain-Based Vehicular Edge Computing. IEEE Consum. Electron. Mag, 10, 14–22. Meyer, Eva, Isabell Welpe, and Philipp Sandner (2021) Decentralized finance — A systematic literature review and research directions. SSRN Electronic Journal 2021: 4016497. Mohan, Vijay (2022) Automated market makers and decentralized exchanges: A DeFi primer. Financial Innovation 8: 1–48. Momtaz, Paul P. (2022) How efficient is Decentralized Finance (DeFi)? SSRN Electronic Journal 2022: 4063670. Mohan, V. (2022). Automated market makers and decentralized exchanges: A DeFi primer. Financial Innovation, 8(1), 20. Platt, Moritz, and Peter McBurney (2023) Sybil in the Haystack: A Comprehensive Review of Blockchain Consensus Mechanisms in Search of Strong Sybil Attack Resistance. Algorithms 16, no. 1: 34. https://doi.org/10.3390/a16010034 Popescu, A. D. (2020). Decentralized finance (defi)–the lego of finance. Social Sciences and Education Research Review, 7(1), 321–349. Raju A. and V. Udayashankara (2018) A survey on unimodal, multimodal biometrics and its fusion techniques,” International Journal of Engineering and Technology(UAE), vol. 7, pp. 689–695. Raheem, E. A., Ahmad, S. M. S., & Adnan, W. A. W. (2019). Insight on face liveness detection: A systematic literature review. International Journal of Electrical and Computer Engineering, 9(6), 5865. Ross, A., Banerjee, S., Chen, C., Chowdhury, A., Mirjalili, V., Sharma, R., & Yadav, S. (2019). Some research problems in biometrics: The future beckons. In 2019 International Conference on Biometrics (ICB) (pp. 1–8). IEEE. Qin, Kaihua, Liyi Zhou, Yaroslav Afonin, Ludovico Lazzaretti, and Arthur Gervais. (2021) CeFi vs. DeFi — Comparing Centralized to Decentralized Finance. arXiv arXiv:2106.08157. Schär, F. (2021). Decentralized finance: On blockchain-and smart contract-based financial markets. FRB of St. Louis Review. Schueffel, P. (2021). DeFi: Decentralized Finance-An Introduction and Overview. Journal of Innovation Management, 9(3), I-XI. Sun, X., & Stasinakis, C. (2021). Decentralization illusion in DeFi: Evidence from MakerDAO. Available at SSRN 3971791. Sun, Xinyuan, Shaokai Lin, Vilhelm Sjöberg, and Jay Jie. (2021) How to Exploit a DeFi Project. Berlin/Heidelberg: Springer, pp. 162–67. Siddarth, D., Ivliev, S., Siri, S., & Berman, P. (2020). Who Watches the Watchmen? A Review of Subjective Approaches for Sybil-Resistance in Proof of Personhood Protocols. Frontiers in Blockchain. https://doi.org/10.3389/fbloc.2020.590171 Shilina, S. (2023) Revolutionizing identity verification: An introduction to Proof of Personhood (PoP) protocols. Turing, A. M. (1950). Computing machinery and intelligence. Mind, 59(236), 433–460. Von Ahn, L., Maurer, B., McMillen, C., Abraham, D., & Blum, M. (2008). reCAPTCHA: Human-Based Character Recognition via Web Security Measures. Science, 321(5895), 1465–1468. Wang, Y., Zuest, P., Yao, Y., Lu, Z., & Wattenhofer, R. (2022). Impact and user perception of sandwich attacks in the defi ecosystem. In Proceedings of the 2022 CHI Conference on Human Factors in Computing Systems (pp. 1–15). Woodward, J. D. (1997). Biometrics: Privacy’s foe or privacy’s friend?. Proceedings of the IEEE, 85(9), 1480–1492. Xu, X. Weber, I. Staples, M. (2019) Architecture for Blockchain Applications; Springer International Publishing: Cham, Switzerland. Yu, H., Gibbons, P. B., Kaminsky, M., & Xiao, F. (2008). Sybillimit: A near-optimal social network defense against Sybil attacks. In 2008 IEEE Symposium on Security and Privacy (sp 2008) (pp. 3–17). IEEE. Zetzsche, D. A., Arner, D. W., & Buckley, R. P. (2020). Decentralized finance (defi). Journal of Financial Regulation, 6, 172–203. Zetzsche, Dirk Andreas, and Linn Anker-Sorensen (2021) From Centralized to Decentralized Finance: The Issue of Fake-DeFi. SSRN Electronic Journal 2021: 3978815. Zmaznev, E. (2021) Measuring Decentralized Finance Regulatory Uncertainty. Bergen: Norwegian School of Economics, pp. 1–43. Zheng, Z., Xie, S., Dai, H. N., Chen, W., Chen, X., Weng, J., & Imran, M. (2020). An overview on smart contracts: Challenges, advances and platforms. Future Generation Computer Systems, 105, 475–491. Zwitter, A., & Hazenberg, J. (2020). Decentralized network governance: blockchain technology and the future of regulation. Frontiers in Blockchain, 3, 12. Also published . here