Implementing the ConsensusState interface

A ConsensusState is the snapshot of the counterparty chain, that an IBC client uses to verify proofs (e.g. a block).

The further development of multiple types of IBC light clients and the difficulties presented by this generalization problem (see ADR-006 for more information about this historical context) led to the design decision of each client keeping track of and set its own ClientState and ConsensusState, as well as the simplification of client ConsensusState updates through the generalized ClientMessage interface.

The below ConsensusState interface is a generalized interface for the types of information a ConsensusState could contain. For a reference ConsensusState implementation, please see the Tendermint light client ConsensusState.

ClientType method

This is the type of client consensus. It should be the same as the ClientType return value for the corresponding ClientState implementation.

GetTimestamp method

GetTimestamp should return the timestamp (in nanoseconds) of the consensus state snapshot. This function has been deprecated and will be removed in a future release.

ValidateBasic method

ValidateBasic should validate every consensus state field and should return an error if any value is invalid. The light client implementer is in charge of determining which checks are required.