accounts/scwallet: fix public key confirmation regression

accounts/scwallet/wallet.go

@@ -982,12 +982,10 @@ func (s *Session) derive(path accounts.DerivationPath) (accounts.Account, error)
 	copy(sig[32-len(rbytes):32], rbytes)
 	copy(sig[64-len(sbytes):64], sbytes)
 
-	pubkey, err := determinePublicKey(sig, sigdata.PublicKey)
-	if err != nil {
+	if err := confirmPublicKey(sig, sigdata.PublicKey); err != nil {
 		return accounts.Account{}, err
 	}
-
-	pub, err := crypto.UnmarshalPubkey(pubkey)
+	pub, err := crypto.UnmarshalPubkey(sigdata.PublicKey)
 	if err != nil {
 		return accounts.Account{}, err
 	}
@@ -1057,10 +1055,10 @@ func (s *Session) sign(path accounts.DerivationPath, hash []byte) ([]byte, error
 	return sig, nil
 }
 
-// determinePublicKey uses a signature and the X component of a public key to
-// recover the entire public key.
-func determinePublicKey(sig, pubkeyX []byte) ([]byte, error) {
-	return makeRecoverableSignature(DerivationSignatureHash[:], sig, pubkeyX)
+// confirmPublicKey confirms that the given signature belongs to the specified key.
+func confirmPublicKey(sig, pubkey []byte) error {
+	_, err := makeRecoverableSignature(DerivationSignatureHash[:], sig, pubkey)
+	return err
 }
 
 // makeRecoverableSignature uses a signature and an expected public key to