Cross-chain is one of the problems that the public chain field is trying to solve. Different projects have their own technical implementation methods, and the cross-chain project that Odaily has recently contactedASCH Chain (ASCH)Said that it mainly adopts the scheme based on the side chain.
Shan Qingfeng, the founder of Ashchain, said that when the sidechain was first proposed, it was mainly a one-way docking of the main chain assets, and the transfer of Bitcoin assets to the sidechain was used. This is the most primitive concept of the sidechain. Afterwards, the meaning has been expanded. In theory, any chain can have its own side chain, and then transfer its own assets to other chains; since a side chain can connect to one type of asset, it can also connect to multiple assets. When a "side chain" links many main chains, it becomes a relay chain.
Ashchain was born in 2016. It was originally a Bitcoin sidechain application development platform, hoping to increase the transfer speed of Bitcoin, reduce transaction costs and expand usage scenarios. With the development of the above concepts, its current positioning is a blockchain application development platform based on a multi-chain architecture. For example, when a side chain supports both BTC and BCH, both BTC and BCH can be "recharged" to this chain, exchanged or circulated on this chain, and of course can also be "withdrawal" back to the original chain. This chain is like an asset exchange place, supporting various public chain currencies; applications developed on this chain can support payment in various currencies. Small games developed on the ASCH chain can be paid with the token XAS of the ASCH chain, or can be played with BTC and BCH.
It can be seen that the ASCH chain is like an intermediary between chains. In this process, the key is how to ensure that the information transmission between Bitcoin and other chains and the ASCH chain is correct. Ashchain uses a decentralized cross-chain gateway as a processing mechanism.
The cross-chain gateway is a relay network and multi-signature account jointly maintained by multiple nodes elected by the proposal system. The cross-chain gateway is mainly responsible for reading the account information on their respective public chains; jointly locking and unlocking the digital assets to be cross-chained under an account; passing the situation of the cross-chain digital assets that can be controlled to another public chain. The reason why the gateway can do this is mainly because its nodes have installed the node clients of the two chains, and at the same time assume the role of the full node of the other main chain and the super node of the ASCH chain, so they can read the data of the two chains. Information, it can monitor the account on the Bitcoin chain, and let the corresponding account on the ASCH chain increase Bitcoin assets; and vice versa. The correspondence between accounts is recorded on the ASCH chain.
The consensus mechanism used by the ASCH chain is DPOS+PBFT, the validator election uses the DPOS mechanism, and the block generation uses PBFT to reach a consensus. In order to ensure the reliability of the information, a single node can be responsible for the operation of the gateway. The general gateway is composed of multiple nodes. The current design is 5-21. It is hoped to find a more authoritative subject operation in the corresponding project (such as the BCH project party), through the district The openness and transparency of the block chain and the economic reward and punishment mechanism regulate the behavior of nodes. To sum it up, it is a trusted institution + mortgage mechanism. Shan Qingfeng said that account management generally uses technologies such as multi-signature and zero-knowledge proof, plus a fault-tolerant model. At present, the ASCH chain uses a multi-signature mechanism.
According to the description of ASCH chain, users need to "recharge" BTC to the ASCH chain, and they need to transfer BTC to the gateway account on the Bitcoin chain first; after the cross-chain gateway receives the information, it locks the gateway account and verifies it. After most After the node is verified; the gateway will unlock equivalent digital assets for the user on the ASCH chain, and the user can use BTC on the ASCH chain. BTC and XAS seem to be merchants in two countries. The two parties cannot trust each other and use different currencies, so they cannot trade directly. Therefore, the two parties negotiated a set of rules (equivalent to the cross-chain gateway protocol) and set up a special trading place to process transactions, jointly managed by the country's prestigious businessmen (equivalent to gateway nodes) as representatives. Need to have a sufficient amount of assets as collateral.
The ASCH chain mainnet has been in operation for 2 years, and has realized cross-chain assets of ASCH (XAS), Bitcoin (BTC) and Bitcoin Cash (BCH) respectively, and plans to support ETH in the third quarter of this year. At present, Ashchain has released its own wallet DAPP; dozens of DAPPs including CCTime, Kong Mingwu, and Virtual Earth have been developed and are waiting to be launched.
In September 2016, V God proposed three cross-chain solutions in a cross-chain technical report provided to R3: notary mode, side chain/relay mode and hash lock mode. According to the report, the notary model is actually through a group of individuals or alliances who are responsible for the nodes of the two chains at the same time, telling the B chain what happened on the A chain, such as Interledger, an open protocol for cross-ledger value transmission developed by Ripple, but it is not a chain. , is just a set of gateway protocols; the side chain is that the B chain "directly" verifies the transactions on the A chain through information such as verifying the block header of the A chain and the Merkle tree, such as the BTC Relay on the Ethereum. It can only achieve one-way anchoring (because the Bitcoin scripting language does not support it). On the one hand, a Relayer in the Ethereum network is required to continuously submit information to the contract to earn user fees. Shan Qingfeng believes that packaging the block headers on the chain "is relatively expensive and has no versatility. It solves the problem of Bitcoin but cannot solve the problem of Ethereum."
The more well-known cross-chain projects include Cosmos and Polkadot, but neither of them has landed. In Cosmos, different spaces (Zones, independent blockchains) communicate with the "hub" (Hub, which manages many zones) through the IBC (blockchain communication) protocol, and information packages in different spaces are transmitted through the center. In order to ensure that the transmission is correct, a proof (Merkle-proof) needs to be published on the receiver's blockchain. In order to verify this proof, the receiver needs to know the block header of the sender at all times, similar to the mechanism adopted by the side chain. The blocks of the Polkadot relay chain contain the block header of the parachain, and some confirmation information to avoid double spending. Validators operate relay chain nodes and validate blocks on parachains; there may also be a collator running full nodes of a particular parachain responsible for submitting new blocks.
Odaily has also previously reported on Wanchain and Bitcoin sidechain RSK. According to different technical solutions and main directions of attack, Shan Qingfeng said that hash locking is for asset transfer, and the biggest feature of ASCH chain is that asset transfer is for application. "Smart contract is a very advanced technology. Many usage scenarios are in a centralized environment. Decentralized asset trading is just an application that can become a supplement to centralized exchanges. However, smart contracts have many application scenarios." He said that Ethereum's smart contract has the largest developer community, but it does not support cross-chain, and Bitcoin does not support smart contracts. Ashchain plans to support Ethereum's smart contracts in the future, and the application scenarios of BTC and ETH can be expanded.
August this yearReference article:
Reference article:
Download the cross-chain technical report provided by Vitalik to R3: Chain Interoperability（Simple Chinese translation of the report）
In-depth analysis of streaming cross-chain technology
In-depth understanding of cross-chain technology
Cross-chain combing of side chains and a brief review of OneLedger
Detailed explanation of the cross-chain technology Interledger Protocol (ILP) proposed by Ripple
