Question concerning verifying a transaction signer.

[JuergenSimon]

HI there. This is not an issue report but I have a question around verifying if a transaction was signed by a certain person using steem.js code and I'm having trouble finding someone who can help. Assuming I have an blockchain transaction, signed with a private posting key. I had success getting the signature using this code:

const Signature = require('steem/lib/auth/ecc/src/signature');
const signature = Signature.fromHex(signedTransaction.signatures[0]);

Now I pull the public key from the get_accounts operation and can construct an object like so:

const PublicKey = require('steem/lib/auth/ecc/src/key_public');
const publicKey = PublicKey.fromString(profile['posting'].key_auths[0][0]);

So far so good. But now I want to figure out if the transaction was signed by the private posting key belonging to the public posting key. I try the following code:

const Operations = require('steem/lib/auth/serializer/src/operations');
const buffer = Operations.signed_transaction.toBuffer(signedTransaction);
const isValid = signature.verifyHex(buffer.toString('hex'), publicKey);

Since the transaction was signed with the user's private posting key, I would expect the signature to verify that. However, the result is always false. What am I overlooking?