Table of contents
1. Notary mechanism
Introduce a trusted third party to automatically or request to monitor events on different chains, and reach a consensus on whether the event occurs through a specific consensus algorithm, and finally respond in time.
1.1 Single Signature Notary
Also known as a centralized notary, that is to designate an independent node or institution to act as a notary. The notary undertakes the tasks of data collection, verification, and transaction confirmation during the cross-chain interaction process, and acts as a conflict arbitrator, thereby realizing Replace technical reputation guarantees with trusted third parties.
Features: Strong compatibility and fast processing speed, but the scope of application is relatively single, and most of them are used for cross-chain asset exchange.
1.2 Multi-signature notary
In the multi-signature notary model, the notary is usually a group of independent nodes or organizations, and each node has a key. The transaction can only be confirmed.
Features: It weakens the risk of centralization and has higher security. When some nodes are maliciously attacked, it will not affect the operation of the entire cross-chain system.
1.3 Distributed multi-signature notary
The implementation process of the distributed signature notary mode is to split the unique key generated based on cryptography into multiple fragments, and distribute the processed fragments randomly to the drawn notaries, even if all the notaries put the fragments together The key cannot be obtained, and the complete key can only be pieced together after a certain percentage of notaries allowed to complete the signature together, thereby achieving a more decentralized cross-chain interaction. Features: higher security and
reliability
2. Sidechain/Relay
There is no strict distinction between side chains and relays. From a formal point of view, side chains focus on expressing the master-slave relationship between chains, and relays are technologies or solutions to achieve cross-chains.
2.1 Sidechain
The side chain is relative to the main chain. The main chain does not know the existence of the side chain, but the side chain knows the existence of the main chain. Assets are transferred to the side chain for processing, thereby reducing the pressure on the main chain and achieving the purpose of expanding the functions and performance of the main chain. The core principle of side chain implementation is the two-way peg technology.
2.2 Relay
The relay is a cross-chain operation layer abstracted from each main chain. It provides a unified language, and only collects the data status between the two chains through the middleman for self-verification, which can reduce the security risks of communication between the links. Suitable for linking 2 heterogeneous or homogeneous blockchains.
Difference: In terms of affiliation, the side chain is subordinate to the main chain, which mainly focuses on optimizing the scalability of the blockchain; the relay has no affiliation and focuses on the transmission of cross-chain data. From the point of view of the execution process, since the side chain needs to synchronize all block headers during the transaction processing process, the speed of the side chain is slower than that of the relay [29,31]. In terms of security, the security mechanisms of the side chain and the main chain are independent. Since the security of the side chain is based on the transaction consistency verification based on the incentive mechanism, the security of the main chain cannot be It works on the side chain; the relay is completely verified by the main chain itself, so it has higher security performance.
3. Hash locking
The full name of Hash lock is Hash time lock contract (Hash timelock contract), which is a cross-chain technical solution to complete inter-chain asset exchange through hash lock and time lock without the need for a trusted notary.
References:
[1] Shuai He, Xiangnian Xiang, Xiaoliang Chen. A Review of Blockchain Cross-Chain Technology Development and Application Research [J]. Journal of Xihua University (Natural Science Edition), 2021, 40(3): 1 − 14