refactor(core/cardano): introduce derive_public_key to simplify pub key derivation

core/src/apps/cardano/address.py

@@ -2,12 +2,10 @@ from trezor import wire
 from trezor.crypto import base58, hashlib
 from trezor.messages import CardanoAddressType
 
-from apps.common.seed import remove_ed25519_prefix
-
 from .byron_address import derive_byron_address, validate_byron_address
 from .helpers import INVALID_ADDRESS, NETWORK_MISMATCH, bech32, network_ids
 from .helpers.paths import SCHEMA_STAKING_ANY_ACCOUNT
-from .helpers.utils import variable_length_encode
+from .helpers.utils import derive_public_key, variable_length_encode
 from .seed import is_byron_path, is_shelley_path
 
 if False:
@@ -146,8 +144,7 @@ def _get_address_network_id(address: bytes) -> int:
 
 
 def get_public_key_hash(keychain: seed.Keychain, path: list[int]) -> bytes:
-    node = keychain.derive(path)
-    public_key = remove_ed25519_prefix(node.public_key())
+    public_key = derive_public_key(keychain, path)
     return hashlib.blake2b(data=public_key, outlen=28).digest()
 
 

core/src/apps/cardano/auxiliary_data.py

@@ -4,11 +4,11 @@ from trezor.messages import CardanoAddressType
 
 from apps.common import cbor
 
-from ..common.seed import remove_ed25519_prefix
 from .address import derive_address_bytes, derive_human_readable_address
 from .helpers import INVALID_AUXILIARY_DATA, bech32
 from .helpers.bech32 import HRP_JORMUN_PUBLIC_KEY
 from .helpers.paths import SCHEMA_STAKING_ANY_ACCOUNT
+from .helpers.utils import derive_public_key
 from .layout import confirm_catalyst_registration, show_auxiliary_data_hash
 
 if False:
@@ -172,8 +172,9 @@ def _cborize_catalyst_registration(
     protocol_magic: int,
     network_id: int,
 ) -> CatalystRegistration:
-    staking_node = keychain.derive(catalyst_registration_parameters.staking_path)
-    staking_key = remove_ed25519_prefix(staking_node.public_key())
+    staking_key = derive_public_key(
+        keychain, catalyst_registration_parameters.staking_path
+    )
 
     catalyst_registration_payload: CatalystRegistrationPayload = {
         1: catalyst_registration_parameters.voting_public_key,

core/src/apps/cardano/byron_address.py

@@ -2,12 +2,11 @@ from trezor import log
 from trezor.crypto import crc, hashlib
 
 from apps.common import cbor
-from apps.common.seed import remove_ed25519_prefix
 
 from .helpers import INVALID_ADDRESS, NETWORK_MISMATCH, protocol_magics
+from .helpers.utils import derive_public_key
 
 if False:
-    from trezor.crypto import bip32
     from . import seed
 
 PROTOCOL_MAGIC_KEY = 2
@@ -30,11 +29,9 @@ def _encode_address_raw(address_data_encoded: bytes) -> bytes:
 def derive_byron_address(
     keychain: seed.Keychain, path: list, protocol_magic: int
 ) -> bytes:
-    node = keychain.derive(path)
-
     address_attributes = get_address_attributes(protocol_magic)
 
-    address_root = _get_address_root(node, address_attributes)
+    address_root = _get_address_root(keychain, path, address_attributes)
     address_type = 0
     address_data = [address_root, address_attributes, address_type]
     address_data_encoded = cbor.encode(address_data)
@@ -119,6 +116,8 @@ def _address_hash(data: list) -> bytes:
     return res
 
 
-def _get_address_root(node: bip32.HDNode, address_attributes: dict) -> bytes:
-    extpubkey = remove_ed25519_prefix(node.public_key()) + node.chain_code()
+def _get_address_root(
+    keychain: seed.Keychain, path: list[int], address_attributes: dict
+) -> bytes:
+    extpubkey = derive_public_key(keychain, path, extended=True)
     return _address_hash([0, [0, extpubkey], address_attributes])

core/src/apps/cardano/get_public_key.py

@@ -6,10 +6,10 @@ from trezor.messages.HDNodeType import HDNodeType
 from trezor.ui.layouts import show_pubkey
 
 from apps.common import paths
-from apps.common.seed import remove_ed25519_prefix
 
 from . import seed
 from .helpers.paths import SCHEMA_PUBKEY
+from .helpers.utils import derive_public_key
 
 if False:
     from trezor.messages.CardanoGetPublicKey import CardanoGetPublicKey
@@ -44,7 +44,7 @@ def _get_public_key(
 ) -> CardanoPublicKey:
     node = keychain.derive(derivation_path)
 
-    public_key = hexlify(remove_ed25519_prefix(node.public_key())).decode()
+    public_key = hexlify(derive_public_key(keychain, derivation_path)).decode()
     chain_code = hexlify(node.chain_code()).decode()
     xpub_key = public_key + chain_code
 
@@ -53,7 +53,7 @@ def _get_public_key(
         child_num=node.child_num(),
         fingerprint=node.fingerprint(),
         chain_code=node.chain_code(),
-        public_key=remove_ed25519_prefix(node.public_key()),
+        public_key=derive_public_key(keychain, derivation_path),
     )
 
     return CardanoPublicKey(node=node_type, xpub=xpub_key)

core/src/apps/cardano/helpers/utils.py

@@ -1,9 +1,13 @@
 from trezor.crypto import hashlib
 
 from apps.cardano.helpers.paths import ACCOUNT_PATH_INDEX, unharden
+from apps.common.seed import remove_ed25519_prefix
 
 from . import bech32
 
+if False:
+    from .. import seed
+
 
 def variable_length_encode(number: int) -> bytes:
     """
@@ -58,3 +62,11 @@ def format_asset_fingerprint(policy_id: bytes, asset_name_bytes: bytes) -> str:
     ).digest()
 
     return bech32.encode("asset", fingerprint)
+
+
+def derive_public_key(
+    keychain: seed.Keychain, path: list[int], extended: bool = False
+) -> bytes:
+    node = keychain.derive(path)
+    public_key = remove_ed25519_prefix(node.public_key())
+    return public_key if not extended else public_key + node.chain_code()

core/src/apps/cardano/sign_tx.py

@@ -9,7 +9,6 @@ from trezor.messages.CardanoSignedTxChunkAck import CardanoSignedTxChunkAck
 
 from apps.common import cbor, safety_checks
 from apps.common.paths import validate_path
-from apps.common.seed import remove_ed25519_prefix
 
 from . import seed
 from .address import (
@@ -49,7 +48,7 @@ from .helpers.paths import (
     SCHEMA_STAKING,
     SCHEMA_STAKING_ANY_ACCOUNT,
 )
-from .helpers.utils import to_account_path
+from .helpers.utils import derive_public_key, to_account_path
 from .layout import (
     confirm_certificate,
     confirm_sending,
@@ -510,7 +509,7 @@ def _cborize_shelley_witness(
     signature = ed25519.sign_ext(
         node.private_key(), node.private_key_ext(), tx_body_hash
     )
-    public_key = remove_ed25519_prefix(node.public_key())
+    public_key = derive_public_key(keychain, path)
 
     return public_key, signature
 
@@ -532,7 +531,7 @@ def _cborize_byron_witnesses(
     for path in paths:
         node = keychain.derive(list(path))
 
-        public_key = remove_ed25519_prefix(node.public_key())
+        public_key = derive_public_key(keychain, list(path))
         signature = ed25519.sign_ext(
             node.private_key(), node.private_key_ext(), tx_body_hash
         )