feat: add DER encoding methods and update key type alias in key_utils

Signed-off-by: MonaaEid <monaa_eid@hotmail.com>

Author: MonaaEid

src/hiero_sdk_python/utils/key_utils.py

@@ -7,47 +7,30 @@
 
 from __future__ import annotations
 
-from hiero_sdk_python.crypto.key import Key as SdkKey
-from hiero_sdk_python.crypto.private_key import PrivateKey
-from hiero_sdk_python.crypto.public_key import PublicKey
+from hiero_sdk_python.crypto.key import Key
 from hiero_sdk_python.hapi.services import basic_types_pb2
 
 
-# Type alias for keys that can be either PrivateKey or PublicKey
-Key = PrivateKey | PublicKey | SdkKey
-
-
 def key_to_proto(key: Key | None) -> basic_types_pb2.Key | None:
     """
-    Helper function to convert a key (PrivateKey or PublicKey) to protobuf Key format.
+    Helper function to convert an SDK key to protobuf Key format.
 
-    This function handles the conversion of SDK key types to protobuf format:
-    - If a PrivateKey is provided, its corresponding public key is extracted and converted.
-    - If a PublicKey is provided, it is converted directly to protobuf.
-    - If None is provided, None is returned.
+    This function handles any concrete subclass of Key by delegating to its
+    to_proto_key() implementation. If None is provided, None is returned.
 
     Args:
-        key (Optional[Key]): The key to convert (PrivateKey or PublicKey), or None
+        key (Optional[Key]): The key to convert, or None
 
     Returns:
         basic_types_pb2.Key (Optional): The protobuf key or None if key is None
 
     Raises:
-        TypeError: If the provided key is not a PrivateKey, PublicKey, or None.
+        TypeError: If the provided key is not a Key instance or None.
     """
     if key is None:
         return None
 
-    # If it's a PrivateKey, get the public key first, then convert to proto
-    if isinstance(key, PrivateKey):
-        return key.public_key()._to_proto()
-
-    # If it's a PublicKey, convert directly to proto
-    if isinstance(key, PublicKey):
-        return key._to_proto()
-
-    # Any other SDK Key implementation (e.g., KeyList / ThresholdKey wrapper)
-    if isinstance(key, SdkKey):
+    if isinstance(key, Key):
         return key.to_proto_key()
 
-    raise TypeError("Key must be of type PrivateKey or PublicKey, or another SDK Key implementation")
+    raise TypeError("Key must be of type PrivateKey or PublicKey")

tests/unit/token_create_transaction_test.py

@@ -64,6 +64,16 @@ def generate_transaction_id(account_id_proto):
     return TransactionId(valid_start=tx_timestamp, account_id=account_id_proto)
 
 
+def _mock_private_key(public_key_bytes: bytes, signature: bytes) -> MagicMock:
+    """Create a PrivateKey mock that returns a stable protobuf key representation."""
+    key = MagicMock(spec=PrivateKey)
+    key.sign.return_value = signature
+    key.public_key().to_bytes_raw.return_value = public_key_bytes
+    key.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=public_key_bytes)
+    key.to_proto_key.return_value = basic_types_pb2.Key(ed25519=public_key_bytes)
+    return key
+
+
 ########### Basic Tests for Building Transactions ###########
 
 
@@ -311,40 +321,14 @@ def test_sign_transaction(mock_account_ids, mock_client):
     private_key.sign.return_value = b"signature"
     private_key.public_key().to_bytes_raw.return_value = b"public_key"
 
-    private_key_admin = MagicMock(spec=PrivateKey)
-    private_key_admin.sign.return_value = b"admin_signature"
-    private_key_admin.public_key().to_bytes_raw.return_value = b"admin_public_key"
-    private_key_admin.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"admin_public_key")
-
-    private_key_supply = MagicMock(spec=PrivateKey)
-    private_key_supply.sign.return_value = b"supply_signature"
-    private_key_supply.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"supply_public_key")
-
-    private_key_freeze = MagicMock(spec=PrivateKey)
-    private_key_freeze.sign.return_value = b"freeze_signature"
-    private_key_freeze.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"freeze_public_key")
-
-    private_key_wipe = MagicMock(spec=PrivateKey)
-    private_key_wipe.sign.return_value = b"wipe_signature"
-    private_key_wipe.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"wipe_public_key")
-
-    private_key_metadata = MagicMock(spec=PrivateKey)
-    private_key_metadata.sign.return_value = b"metadata_signature"
-    private_key_metadata.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"metadata_public_key")
-
-    private_key_pause = MagicMock(spec=PrivateKey)
-    private_key_pause.sign.return_value = b"pause_signature"
-    private_key_pause.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"pause_public_key")
-
-    private_key_kyc = MagicMock(spec=PrivateKey)
-    private_key_kyc.sign.return_value = b"kyc_signature"
-    private_key_kyc.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"kyc_public_key")
-
-    private_key_fee_schedule = MagicMock(spec=PrivateKey)
-    private_key_fee_schedule.sign.return_value = b"fee_schedule_signature"
-    private_key_fee_schedule.public_key()._to_proto.return_value = basic_types_pb2.Key(
-        ed25519=b"fee_schedule_public_key"
-    )
+    private_key_admin = _mock_private_key(b"admin_public_key", b"admin_signature")
+    private_key_supply = _mock_private_key(b"supply_public_key", b"supply_signature")
+    private_key_freeze = _mock_private_key(b"freeze_public_key", b"freeze_signature")
+    private_key_wipe = _mock_private_key(b"wipe_public_key", b"wipe_signature")
+    private_key_metadata = _mock_private_key(b"metadata_public_key", b"metadata_signature")
+    private_key_pause = _mock_private_key(b"pause_public_key", b"pause_signature")
+    private_key_kyc = _mock_private_key(b"kyc_public_key", b"kyc_signature")
+    private_key_fee_schedule = _mock_private_key(b"fee_schedule_public_key", b"fee_schedule_signature")
 
     token_tx = TokenCreateTransaction()
     token_tx.set_token_name("MyToken")
@@ -778,40 +762,14 @@ def test_build_and_sign_nft_transaction_to_proto(mock_account_ids, mock_client):
     private_key_private.sign.return_value = b"private_signature"
     private_key_private.public_key().to_bytes_raw.return_value = b"private_public_key"
 
-    private_key_admin = MagicMock(spec=PrivateKey)
-    private_key_admin.sign.return_value = b"admin_signature"
-    private_key_admin.public_key().to_bytes_raw.return_value = b"admin_public_key"
-    private_key_admin.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"admin_public_key")
-
-    private_key_supply = MagicMock(spec=PrivateKey)
-    private_key_supply.sign.return_value = b"supply_signature"
-    private_key_supply.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"supply_public_key")
-
-    private_key_freeze = MagicMock(spec=PrivateKey)
-    private_key_freeze.sign.return_value = b"freeze_signature"
-    private_key_freeze.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"freeze_public_key")
-
-    private_key_wipe = MagicMock(spec=PrivateKey)
-    private_key_wipe.sign.return_value = b"wipe_signature"
-    private_key_wipe.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"wipe_public_key")
-
-    private_key_metadata = MagicMock(spec=PrivateKey)
-    private_key_metadata.sign.return_value = b"metadata_signature"
-    private_key_metadata.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"metadata_public_key")
-
-    private_key_pause = MagicMock(spec=PrivateKey)
-    private_key_pause.sign.return_value = b"pause_signature"
-    private_key_pause.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"pause_public_key")
-
-    private_key_kyc = MagicMock(spec=PrivateKey)
-    private_key_kyc.sign.return_value = b"kyc_signature"
-    private_key_kyc.public_key()._to_proto.return_value = basic_types_pb2.Key(ed25519=b"kyc_public_key")
-
-    private_key_fee_schedule = MagicMock(spec=PrivateKey)
-    private_key_fee_schedule.sign.return_value = b"fee_schedule_signature"
-    private_key_fee_schedule.public_key()._to_proto.return_value = basic_types_pb2.Key(
-        ed25519=b"fee_schedule_public_key"
-    )
+    private_key_admin = _mock_private_key(b"admin_public_key", b"admin_signature")
+    private_key_supply = _mock_private_key(b"supply_public_key", b"supply_signature")
+    private_key_freeze = _mock_private_key(b"freeze_public_key", b"freeze_signature")
+    private_key_wipe = _mock_private_key(b"wipe_public_key", b"wipe_signature")
+    private_key_metadata = _mock_private_key(b"metadata_public_key", b"metadata_signature")
+    private_key_pause = _mock_private_key(b"pause_public_key", b"pause_signature")
+    private_key_kyc = _mock_private_key(b"kyc_public_key", b"kyc_signature")
+    private_key_fee_schedule = _mock_private_key(b"fee_schedule_public_key", b"fee_schedule_signature")
 
     # Build the transaction
     token_tx = TokenCreateTransaction()