From d28967cf54c4095bdfa39e13a7f42d1455b42221 Mon Sep 17 00:00:00 2001
From: Alex Barnsley <8069294+alexbarnsley@users.noreply.github.com>
Date: Thu, 21 May 2026 16:12:40 +0100
Subject: [PATCH] feat: add legacy address handling

---
 crypto/identity/legacy_address.py     | 35 +++++++++++++++++++++++++++
 tests/identity/conftest.py            | 12 +++++++++
 tests/identity/test_legacy_address.py | 32 ++++++++++++++++++++++++
 3 files changed, 79 insertions(+)
 create mode 100644 crypto/identity/legacy_address.py
 create mode 100644 tests/identity/test_legacy_address.py

diff --git a/crypto/identity/legacy_address.py b/crypto/identity/legacy_address.py
new file mode 100644
index 0000000..28b8633
--- /dev/null
+++ b/crypto/identity/legacy_address.py
@@ -0,0 +1,35 @@
+import hashlib
+
+from base58 import b58decode_check, b58encode_check
+
+from Cryptodome.Hash import RIPEMD160
+
+from crypto.identity.private_key import PrivateKey
+
+
+class LegacyAddress:
+    @classmethod
+    def from_public_key(cls, public_key: str, pub_key_hash: int) -> str:
+        ripemd160 = RIPEMD160.new(bytes.fromhex(public_key))
+        payload = bytes([pub_key_hash]) + ripemd160.digest()
+        return b58encode_check(payload).decode()
+
+    @classmethod
+    def from_private_key(cls, private_key: str, pub_key_hash: int) -> str:
+        public_key = PrivateKey.from_hex(private_key).public_key
+        return cls.from_public_key(public_key, pub_key_hash)
+
+    @classmethod
+    def from_passphrase(cls, passphrase: str, pub_key_hash: int) -> str:
+        private_key = hashlib.sha256(passphrase.encode()).hexdigest()
+        return cls.from_private_key(private_key, pub_key_hash)
+
+    @classmethod
+    def validate(cls, address: str, pub_key_hash: int) -> bool:
+        try:
+            decoded = b58decode_check(address)
+            if len(decoded) != 21:
+                return False
+            return decoded[0] == pub_key_hash
+        except Exception:
+            return False
diff --git a/tests/identity/conftest.py b/tests/identity/conftest.py
index df8a6fb..12bb19e 100644
--- a/tests/identity/conftest.py
+++ b/tests/identity/conftest.py
@@ -17,6 +17,18 @@ def identity():
     }
     return data
 
+@pytest.fixture
+def legacy_identity():
+    return {
+        'data': {
+            'public_key': '02a7c5ca78f6abbced169cb883aec3ffc0a0950affc0de575fb211873b5846e668',
+            'private_key': 'c7a0df6e1c42268946af49af28c49c6da64419f0203fa970b6e9be9f85a44875',
+            'address': 'D6WFwqYDRiFkSf4ezzWRt3jCsUp2sRmDMi',
+        },
+        'passphrase': 'enact busy minimum fantasy endless shoot reduce few inject ostrich snow promote',
+        'pub_key_hash': 30,
+    }
+
 @pytest.fixture
 def sign_compact():
     """Identity fixture
diff --git a/tests/identity/test_legacy_address.py b/tests/identity/test_legacy_address.py
new file mode 100644
index 0000000..f3507fd
--- /dev/null
+++ b/tests/identity/test_legacy_address.py
@@ -0,0 +1,32 @@
+from crypto.identity.legacy_address import LegacyAddress
+
+
+def test_from_passphrase(legacy_identity):
+    address = LegacyAddress.from_passphrase(legacy_identity['passphrase'], legacy_identity['pub_key_hash'])
+    assert address == legacy_identity['data']['address']
+
+
+def test_from_public_key(legacy_identity):
+    address = LegacyAddress.from_public_key(legacy_identity['data']['public_key'], legacy_identity['pub_key_hash'])
+    assert address == legacy_identity['data']['address']
+
+
+def test_from_private_key(legacy_identity):
+    address = LegacyAddress.from_private_key(legacy_identity['data']['private_key'], legacy_identity['pub_key_hash'])
+    assert address == legacy_identity['data']['address']
+
+
+def test_validate(legacy_identity):
+    assert LegacyAddress.validate(legacy_identity['data']['address'], legacy_identity['pub_key_hash']) is True
+
+
+def test_validate_incorrect_pub_key_hash(legacy_identity):
+    assert LegacyAddress.validate(legacy_identity['data']['address'], 32) is False
+
+
+def test_validate_invalid_address(legacy_identity):
+    assert LegacyAddress.validate('D2WFnqYDRiFkSf4ezzWRt3jCsUp2sRmDMifwd', legacy_identity['pub_key_hash']) is False
+
+
+def test_validate_decoding_error(legacy_identity):
+    assert LegacyAddress.validate('invalid', legacy_identity['pub_key_hash']) is False