WIP for ArbitraryKey reversion.

Signed-off-by: Daira-Emma Hopwood <[email protected]>

Author: daira

zcash_test_vectors/zip_0032.py

@@ -40,7 +40,7 @@ def CKDh(Context, sk_par, c_par, i, lead, tag):
 
 
 class RegisteredKey(object):
-    Context = HardenedOnlyContext(b'ZIPRegistered_KD', b'\xAC')
+    Registered = HardenedOnlyContext(b'ZIPRegistered_KD', b'\xAC')
 
     def __init__(self, IKM, path, sk, chaincode, full_width=None):
         self.IKM = IKM
@@ -58,16 +58,16 @@ def master(cls, ContextString, S):
         assert 32 <= length_S <= 252
 
         IKM = bytes([length_ContextString]) + ContextString + bytes([length_S]) + S
-        (sk, chaincode) = MKGh(cls.Context, IKM)
+        (sk, chaincode) = MKGh(cls.Registered, IKM)
         return cls(IKM, [], sk, chaincode)
 
     def child(self, i):
-        (sk_child, c_child) = CKDh(self.Context, self.sk, self.chaincode, i, 0, b"")
+        (sk_child, c_child) = CKDh(self.Registered, self.sk, self.chaincode, i, 0, b"")
         return self.__class__(None, self.path + [i], sk_child, c_child)
 
     def child_with_tag(self, i, tag):
-        (sk_child, c_child) = CKDh(self.Context, self.sk, self.chaincode, i, 0, tag)
-        (left, right) = CKDh(self.Context, self.sk, self.chaincode, i, 1, tag)
+        (sk_child, c_child) = CKDh(self.Registered, self.sk, self.chaincode, i, 0, tag)
+        (left, right) = CKDh(self.Registered, self.sk, self.chaincode, i, 1, tag)
         return self.__class__(None, self.path + [(i, tag)], sk_child, c_child, left + right)
 
 
@@ -112,8 +112,30 @@ def registered_key_derivation_tvs():
     )
 
 
-class ArbitraryKey(RegisteredKey):
-    Context = HardenedOnlyContext(b'ZcashArbitraryKD', b'\xAB')
+class ArbitraryKey(object):
+    Adhoc = HardenedOnlyContext(b'ZcashArbitraryKD', b'\xAB')
+
+    def __init__(self, IKM, path, sk, chaincode, full_width=None):
+        self.IKM = IKM
+        self.path = path
+        self.sk = sk
+        self.chaincode = chaincode
+
+    @classmethod
+    def master(cls, ContextString, S):
+        length_ContextString = len(ContextString)
+        length_S = len(S)
+
+        assert length_ContextString <= 252
+        assert 32 <= length_S <= 252
+
+        IKM = bytes([length_ContextString]) + ContextString + bytes([length_S]) + S
+        (sk, chaincode) = MKGh(cls.Adhoc, IKM)
+        return cls(IKM, [], sk, chaincode)
+
+    def child(self, i):
+        (sk_child, c_child) = CKDh(self.Adhoc, self.sk, self.chaincode, i, 0, b"")
+        return self.__class__(None, self.path + [i], sk_child, c_child)
 
 
 def arbitrary_key_derivation_tvs():