Sidechains are emerging mechanisms that allow tokens and other digital assets from one blockchain to be securely used in a separate blockchain and then be moved back to the original blockchain if needed. Sidechain functionality holds tremendous potential to enhance the capabilities of existing blockchains. How do Sidechains work? A sidechain is a separate that is attached to its parent blockchain using a two-way peg. The two-way peg enables interchangeability of assets at a predetermined rate between the parent blockchain and the sidechain. The original blockchain is usually referred to as the ‘main chain’ and all additional blockchains are referred to as ‘sidechains’. The blockchain platform Ardor refers to its sidechains as ‘childchains’. blockchain A user on the parent chain first has to send their coins to an output address, where the coins become locked so the user is unable to spend them elsewhere. Once the transaction has been completed, a confirmation is communicated across the chains followed by a waiting period for extra security. After the waiting period, the equivalent number of coins is released on the sidechain, allowing the user to access and spend them there. The reverse happens when moving back from a sidechain to the main chain. Federations A federation is a group that serves as an intermediate point between a main chain and one of its sidechains. This group determines when the coins a user has used are locked up and released. The creators of the sidechain can choose the members of the federation. A problem with the federation structure is that it adds another layer between the main chain and the sidechain. Security Sidechains are responsible for their own security. If there isn’t enough mining power to secure a sidechain, it could be hacked. Since each sidechain is independent, if it is hacked or compromised, the damage will be contained within that chain and won’t affect the main chain. Conversely, should the main chain become compromised, the sidechain can still operate, but the peg will lose most of its value. Sidechains need their own miners. These miners can be incentivized through ‘merged mining’, whereby two separate cryptocurrencies, based on the same algorithm, are mined simultaneously. Current Sidechain Platforms 1. (short for Rootstock) has created an open source testnet called Ginger for its sidechains. It has a two-way peg with the Bitcoin blockchain and rewards Bitcoin miners via merged mining. RSK’s goal is to enable the Bitcoin blockchain to have smart contract capabilities and make payments much faster. RSK 2. as a service platform for business: Ardor uses the consensus mechanism. Ardor calls its sidechains ‘childchains’, and they are tightly integrated into the main chain. Security is enhanced because all transactions are processed and secured by parent chain forgers. Most transactions are pushed down to the childchain level, as the parent mainchain retains minimal features. Global entities such as assets and currencies across chains can be accessed through childchains. Ardor’s Blockchain Proof of Stake The Promise of Sidechains Sidechains allow cryptocurrencies to interact with one another. They add flexibility and allow developers to experiment with Beta releases of Altcoins or software updates before pushing them on to the main chain. Traditional banking functions like issuing and tracking ownership of shares can be tested on sidechains before moving them onto main chains. If the security mechanisms for sidechains can be bolstered, sidechain technology holds promise for massive blockchain scalability.