Consensus for Crosschain Communications
Crosschain communications allows information to be communicated between blockchains. Consensus, in the context of crosschain communications, relates to how participants are able to agree on the state of one blockchain and communicate that information to another blockchain such that the information is trusted. This chapter reviews the usage scenarios of crosschain communications: value transfer and atomic swaps, reading, writing, and state pinning. It analyses what attributes must be maintained for permissionless and permissioned blockchains using a crosschain consensus mechanism such that the properties of each blockchain are not compromised. Finally, this chapter reviews the main categories of crosschain communications techniques: Hash Time Locked Contracts, block header relaying (BTC Relay, Pegged Sidechains and Ion), relay chains (Polkadot and Cosmos), and coordination chains with threshold schemes (Atomic Crosschain Transaction).
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