Experimental: Add a function to verify a signature for an address

[mcintyre94]

Motivation

In the deserialize-transanction example, we demonstrate how to verify the signature for a transaction

const signedByAddress = 'ED1WqT2hWJLSZtj4TtTdoovmpMrr7zpkUdbfxmcJR1Fq' as Address;
const signedBySignature = decodedTransaction.signatures[signedByAddress]!;
// We encode the source address to bytes
const sourceAddressBytes = getAddressEncoder().encode(signedByAddress);
// Then we create a public Ed25519 key with those bytes
const signedByPublicKey = await crypto.subtle.importKey('raw', sourceAddressBytes, 'Ed25519', true, ['verify']);
// Now we can verify the signature using that key
const verifiedSignature = await verifySignature(signedByPublicKey, signedBySignature, decodedTransaction.messageBytes);

We could write a helper function that takes as input the bytes purported to have been signed, signature to verify and address, and performs the verification for you.

Example use case

const signedByAddress = 'ED1WqT2hWJLSZtj4TtTdoovmpMrr7zpkUdbfxmcJR1Fq' as Address;
const signedBySignature = decodedTransaction.signatures[signedByAddress]!;
const verifiedSignature = await verifySignatureForAddress(signedByAddress, signedBySignature, decodedTransaction.messageBytes)

Details

• This should just be the code from my example - address to bytes, verify-only public key from bytes, verifySignature call
• We may want to note in documentation that you shouldn't do this if you're going to re-use the key for multiple verifications since it'll re-create the same key multiple times

Alternatively, perhaps we could create a function eg createVerifyPublicKeyForAddress that just gives you the public key for an address, to avoid that potential performance issue?

[steveluscher]

I agree that we shouldn't create a method that internally constructs the public key only to throw it out, lest that be called more than once for the same address. Creating an address-to-public key helper sounds fine though. No need to use ‘verify’ in that function name, since all Ed25519 CryptoKeys have only ['verify'] usage.

[andiz2]

I can take care of this