New returns a new Signer that validates blocks with c and signs them with k.

ErrConsensusChange is returned from ValidateAndSignBlock when a new consensus program is detected.

ErrInvalidKey is returned from SignBlock when the key specified on the Signer is invalid.

BlockSigner validates and signs blocks.

EnclaveClient implements the Signer interface by calling Chain Enclave to sign blocks.

Signer provides the interface for computing the block signature.