Signature verification

[coot]

We need to verify the signatures of messages. Mithril key certificates are explained in this blog post. We can use the cardano-crypt-class library for it, e.g. verifyKES using StandardCrypto.

To implement verification, we need to access raw bytes received from the network; this is enabled by input-output-hk/typed-protocols#74 and #4934. We must avoid re-serialisation.

[coot]

KES signature valiadation in ouroboros-consensus: ref.