it's been years and nobody's implemented this! right now i have a draft 'irc format' proposal that looks like:
sv.satoshi.io t s-sha256.f43a3b0fe7be10206074a8cf565671a4960f61 in the the code, a 'features' dict is used. i recall the protocol might send 'features' around, although they might be flags rather than strings. anyway the nearness to a little normativeness gives me enough reason to glance through ssl norms and see if there's a standard condensed way to list fingerprints of a cert associated with their digests
