fix(packet): PublicKey.KeyIdString must return a valid key id

PublicKey.KeyIdString previously did not compute the key ID correctly for v5 and v6 keys.
This commit fixes the issue by directly using the stored key ID from the struct.

Author: lubux

openpgp/packet/public_key.go

@@ -1048,12 +1048,17 @@ func (pk *PublicKey) VerifyDirectKeySignature(sig *Signature) (err error) {
 // KeyIdString returns the public key's fingerprint in capital hex
 // (e.g. "6C7EE1B8621CC013").
 func (pk *PublicKey) KeyIdString() string {
-	return fmt.Sprintf("%X", pk.Fingerprint[12:20])
+	return fmt.Sprintf("%016X", pk.KeyId)
 }
 
 // KeyIdShortString returns the short form of public key's fingerprint
 // in capital hex, as shown by gpg --list-keys (e.g. "621CC013").
+// This function will return the full key id for v5 and v6 keys
+// since the short key id is undefined for them.
 func (pk *PublicKey) KeyIdShortString() string {
+	if pk.Version >= 5 {
+		return pk.KeyIdString()
+	}
 	return fmt.Sprintf("%X", pk.Fingerprint[16:20])
 }