IOTA Tangle Graph from http://www.tangleblog.com Welcome Hello blockchainer! Today’s topic is an enhanced mutation of — The Tangle of IOTA. blockchain This post serves as a very beginner-level overview of the crypto with , . All the graphs and contents are fully credit to . 9th largest market cap IOTA IOTA’s white paper Update: A speech with topic of delivered by two friends of mine (Alan Yip and Martin Shin) and me, is ready on Youtube: IOTA Tangle and Cryptographic Vulnerabilities, IOTA Tangle and Cryptographic Vulnerabilities Why IOTA? Due to the rapid growth of , the demand for inevitably lifted off. As you might recall, Bitcoin was devised toward the goal of solving the needs of micropayment, but it turned out to be infeasible in two reasons: IoT (Internet of Things) micropayment : As the amount of payment reduces, the relative fee rate rises. Heavy fee Bitcoin requires two types of users: transaction verifier (miners) and transaction issuers (normal users). Lacking the homogeneity among roles, the chance of conflicts remains high, wasting everyone’s resources to solve the conflicts. Separation of roles: Whereas, IOTA Tangle puts forward a better solution. It replaces Blockchain with a , called Tangle. Figure 1 shows a typical DAG. DAG (directed acyclic graph) Figure 1: Directed Acyclic Graph (from ) http://ericsink.com/ What’s Tangle? Tangle is made of sites and nodes: Transactions represented on the graph. Sites: Issuers of transactions. Nodes: Sites are a part of the Tangle graph, containing one or some transactions that relate together. Nodes are the users of IOTA who are eligible to issue transactions. A newly issued transaction is obligated to approve old transactions. Yes, two. Key Rule: TWO The responsibility of approving the new transactions belongs to everyone, specifically, the transaction issuers. It removes the special role of miners and brings equality back to all users. NO MORE MINERs! Relationship between transactions There are two ways that transaction A can be approved by transaction B. One way is that transaction A is approved by transaction B. directly Figure 2: Direct Approval of Transaction Second way allows some transactions (e.g. X, Y) to be placed in between, linking up the relationship of A and B as followed: indirect Figure 3: Indirect Approval of Transaction Who started up Tangle? is the first transaction in Tangle: Genesis transaction It is directly/indirectly approved by all other transactions. It sends tokens from “an address containing all tokens” to other “founder addresses”. How to choose transactions to approve? In the early stage, there is NO such rule for choosing transactions to approve. Nodes are assumed to follow some reference rules since they are usually local devices that belong to the same regions. What is Tip? is a newly issued transaction that has not received any approval. An algorithm called is used to solve conflicts. It runs many times to check which transaction, of the two conflict transactions, is more likely to be approved by a selected tip. Tip tip selection algorithm Tangle is Asynchronous Tangle can tolerate conflicting transactions that popped up asynchronously. It believes that any incorrect transaction would be automatically orphaned, or erased, as Tangle keeps on growing. Propagation incentive for nodes A node will be dropped by its neighbor, when it shows laziness toward propagating transactions. The incentive keeps all nodes working, though they don’t issue transactions that frequent. Terms that matter All the following terms are defined as essential attributes of a transaction. Let’s call it . transaction A The weight of is proportional to the effort put in by its issuer, which can be assumed to be 3^n. Weight (Own weight): transaction A ’s own weight + the sum of own weights of all the followed transactions that directly/indirectly approve . (E.g. In figure 4, transaction D has own weight as 1, and cumulative weight as 6 = D’s own weight + A’s own weight + B’ own weight + C’s own weight = 1 + 1 + 3 + 1.) Cumulative weight: Transaction A transaction A Figure 4: Weights (from IOTA white paper). Own weights at right-bottom. Cumulative weights at left-top, as bold. ’s own weight + the sum of own weights of all previous transactions approved by . (E.g. In figure 5, transaction A has score as 9 = A’s own weight + B’s own weight + D’s own weight + F’s own weight + G’s own weight = 1 + 3 + 1 + 3 + 1.) Score: Transaction A transaction A Figure 5: Score (from IOTA white paper). Score at left-top, in the circle. The length of the longest oriented path to the genesis. Height: The length of the longest reverse-oriented path to certain tips. Depth: For instance, in figure 5, the height of D is 3 (D → F → G → genesis), and the depth of D is 2 (D ← B ← A). What is Cutset? Let’s assume the average time of issuing a transaction is time H. is a group of tips alive at timespan between and , with the following definition: Cutset time t time t + time H Any path from a new transaction to genesis MUST go through the cutset. The smaller the size, the higher the chance that a new transaction can be approved. In the other word, a new transaction has fewer competitors. It used as a checkpoint for DAG pruning and other actions taken to control the growth of Tangle. Strategy of choosing transaction Not good, for it does not encourage approving tips. Random: Good. Tips have a much higher probability to be selected and approved. Random among the top section (section near tips): Low load and high load The load of Tangle determines its efficiency, feasibility, and . security Low load: A small number of tips, usually 1 or 2. A weak inflow of transactions. low network latency and great computational power. Happened when: High load: A large number of tips. Depends on the strategy of choosing transaction. A strong inflow of transaction. high network latency and low computational power, forcing several new transactions to turn to approve the same tips. Happened when: Some transactions might need to wait for a long while before being approved. Disadvantage: Figure 6: Low Load and High Load (from IOTA white paper). Problem of High Load In high load, an unapproved transaction can be missed out, and no longer have the chance to be approved. The owner of transaction can reattach or rebroadcast the transaction, knowing that the tokens will not be sent until the transaction is approved. Any duplicate copies via reattach/rebroadcast will be discarded later. [ 2.6] Great solution ( white paper v1.2 ): source The owner of transaction issues a new empty transaction referencing the missed transaction, so as to help it get approved. Great solution ( white paper v0.6 ): Pick some random tips and approve the top ones, leaving a better chance that the missed transaction might be approved soon. OK solution: How fast the Tangle grow? The speed of growth of the cumulative weight of a given transaction can be examined in two different load contexts: Grow at constant speed. Low load: Grow with increasing speed during adaptation period, and return to a constant speed after the period. For the reason that all new transactions will be guaranteed to indirectly approve this transaction. Shown in figure 7. High load: Figure 7: Growth speed of cumulative weight for a transaction in high load environment (From IOTA white paper). Attacks and Countermeasures Stay tuned! This section is to be discussed in the next post soon. :) Conclusion From the white paper, it can be seen that IOTA Tangle deviates from blockchain and creates its own way of selecting and approving transactions. There is no more miners, and no more blocks. As a DAG implementation, lots of interesting statistics can be computed by nodes to have more insights of its neighbors and the network itself. Aside from the benefits and drawbacks of IOTA, there are far more to be discussed about the potential threats that might overthrow the rosy prospect, and the possible countermeasures that could save it from ruins. Nevertheless, the invention of IOTA still proves its worth. To delve into the details and mathematics, IOTA is here to help! white paper Thanks!! Thanks for your time! Please leave some applauses if you like the post. ;p Feel free to correct me if I got anything wrong. Leave your comments~

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