Read key from cose_key returned in signData()

Question

The following (await window.cardano['<wallet>'].enable()).signData('<addr>', '<payload>')

Returns an object { key: <key>, signature: <sig> }

I'm successfully parsing the key to a CoseKey with ermugo/message-signing in node.js, but struggling to pull the header which contains the key. Reading CIP-0030 I believe it is contained within the headers as x. Could someone explain how I read this in code, please? Thanks for your time.

edit: if there is documentation that explains how to do this please show me the way.

Answer 1

Since it's mentioned in CIP-0030 that the key for the header associated with the public key is -2, I spent some time in the debugger and managed to fetch it with this code.

const coseKey = MessageSigning.COSEKey.from_bytes(Buffer.from(key, 'hex'));

const keyHeaderBytes = coseKey.header(MessageSigning.Label.new_int(MessageSigning.Int.new_i32(-2))).as_bytes();

Not sure if this is the optimal solution but it seems to work. Open to feedback.