base64 keysets detection

Author: lollerfirst

cashu/core/crypto/keys.py

@@ -121,10 +121,49 @@ def derive_keyset_short_id(keyset_id: str) -> str:
     raise ValueError(f"Unsupported keyset version in ID: {keyset_id}")
 
 
+def is_base64_keyset_id(keyset_id: str) -> bool:
+    """
+    Check if a keyset ID is a legacy base64 format (pre-0.15.0).
+    
+    Base64 keyset IDs:
+    - Don't start with "00" or "01" version prefix
+    - Are typically 12 characters long
+    - Are valid base64 strings
+    
+    Args:
+        keyset_id: The keyset ID to check
+        
+    Returns:
+        True if the keyset ID is base64 format, False otherwise
+    """
+    # If it starts with a known version prefix, it's not base64
+    if keyset_id.startswith("00") or keyset_id.startswith("01"):
+        return False
+    
+    # Try to decode as base64 to confirm
+    try:
+        base64.b64decode(keyset_id)
+        return True
+    except Exception:
+        return False
+
+
 def get_keyset_id_version(keyset_id: str) -> str:
-    """Extract the version from a keyset ID."""
+    """
+    Extract the version from a keyset ID.
+    
+    Returns:
+        - "00" for version 0 (hex keyset IDs with 00 prefix)
+        - "01" for version 1 (v2 keyset IDs with 01 prefix)
+        - "base64" for legacy base64 keyset IDs (pre-0.15.0)
+    """
     if len(keyset_id) < 2:
         raise ValueError("Invalid keyset ID: too short")
+    
+    # Check if it's a legacy base64 keyset ID
+    if is_base64_keyset_id(keyset_id):
+        return "base64"
+    
     return keyset_id[:2]
 
 

cashu/wallet/secrets.py

@@ -114,6 +114,7 @@ async def generate_determinstic_secret(
         one as the blinding factor) using versioned derivation.
         
         NUT-13: Uses keyset version to determine derivation method:
+        - Version "base64" (ancient, pre-0.15.0): BIP32 derivation
         - Version "00" (legacy): BIP32 derivation 
         - Version "01" (v2): HMAC-SHA256 derivation
         """
@@ -123,8 +124,8 @@ async def generate_determinstic_secret(
         version = get_keyset_id_version(keyset_id)
         logger.trace(f"Keyset {keyset_id} version: {version}")
 
-        if version == "00":
-            # Legacy BIP32 derivation for version 00 keysets
+        if version == "base64" or version == "00":
+            # BIP32 derivation for base64 (ancient) and version 00 keysets
             return await self._derive_secret_bip32(counter, keyset_id)
         elif version == "01":
             # HMAC-SHA256 derivation for version 01 keysets (per NUT-13 test vectors)

tests/wallet/test_wallet_keysets_v2.py

@@ -16,6 +16,7 @@
 from cashu.core.crypto.keys import (
     derive_keyset_short_id,
     get_keyset_id_version,
+    is_base64_keyset_id,
     is_keyset_id_v2,
 )
 from cashu.wallet.keyset_manager import KeysetManager
@@ -26,6 +27,7 @@
 MNEMONIC = "half depart obvious quality work element tank gorilla view sugar picture humble"
 LEGACY_V1_KEYSET_ID = "009a1f293253e41e"
 V2_KEYSET_ID = "016d1ce32977b2d8a340479336a77dc18db8da3e782c5083a6f33d70bc158056d1"
+BASE64_KEYSET_ID = "yjzQhxghPdrr"
 
 
 @pytest.mark.asyncio
@@ -370,3 +372,44 @@ async def test_error_handling():
 
     with pytest.raises(ValueError, match="Unsupported keyset version"):
         await secrets.generate_determinstic_secret(1)
+
+
+def test_base64_keyset_id_detection():
+    """Test detection of base64 keyset IDs (ancient API v0 format)."""
+    # Test base64 keyset ID is detected correctly
+    assert is_base64_keyset_id(BASE64_KEYSET_ID)
+    assert get_keyset_id_version(BASE64_KEYSET_ID) == "base64"
+    
+    # Test v1 keyset is not detected as base64
+    assert not is_base64_keyset_id(LEGACY_V1_KEYSET_ID)
+    assert get_keyset_id_version(LEGACY_V1_KEYSET_ID) == "00"
+    
+    # Test v2 keyset is not detected as base64
+    assert not is_base64_keyset_id(V2_KEYSET_ID)
+    assert get_keyset_id_version(V2_KEYSET_ID) == "01"
+    
+    # Test that base64 ID is not considered v2
+    assert not is_keyset_id_v2(BASE64_KEYSET_ID)
+
+
+@pytest.mark.asyncio
+async def test_base64_keyset_secret_derivation():
+    """Test that base64 keyset IDs use BIP32 derivation (legacy method)."""
+    secrets = WalletSecrets()
+    secrets.keyset_id = BASE64_KEYSET_ID
+    secrets.seed = b"test_seed_for_base64"
+    secrets.bip32 = BIP32.from_seed(secrets.seed)
+    
+    # Test secret derivation
+    secret, r, path = await secrets.generate_determinstic_secret(1)
+    
+    # Should use BIP32 derivation for base64 keysets
+    assert "m/129372'" in path
+    assert len(secret) == 32
+    assert len(r) == 32
+    
+    # Verify the base64 keyset ID gets converted to integer correctly
+    import base64
+    keyset_id_int = int.from_bytes(base64.b64decode(BASE64_KEYSET_ID), "big") % (2**31 - 1)
+    expected_path = f"m/129372'/0'/{keyset_id_int}'/1'"
+    assert expected_path in path