Type Alias Justification

pub type Justification = (ConsensusEngineId, EncodedJustification);

An abstraction over justification for a block’s validity under a consensus algorithm.

Essentially a finality proof. The exact formulation will vary between consensus algorithms. In the case where there are multiple valid proofs, inclusion within the block itself would allow swapping justifications to change the block’s hash (and thus fork the chain). Sending a Justification alongside a block instead bypasses this problem.

Each justification is provided as an encoded blob, and is tagged with an ID to identify the consensus engine that generated the proof (we might have multiple justifications from different engines for the same block).