fix/identical_to_bitcoin_cores_signature

fixed issue for identical to Bitcoin Core's signature

Author: saikiran57

bitcoinutils/keys.py

@@ -307,6 +307,7 @@ def sign_taproot_input(
         tapleaf_scripts: Optional[Script | list[Script] | list[list[Script]]] | bytes = None,
         sighash: int = TAPROOT_SIGHASH_ALL,
         tweak: bool = True,
+        rand_aux: bytes = None,
     ):
         # get the digest from the transaction object and sign
         # note that when signing a tapleaf we typically won't use tweaked
@@ -324,7 +325,7 @@ def sign_taproot_input(
             tx_digest = tx.get_transaction_taproot_digest(
                 txin_index, utxo_scripts, amounts, 0, sighash=sighash
             )
-        return self._sign_taproot_input(tx_digest, sighash, tapleaf_scripts, tweak)
+        return self._sign_taproot_input(tx_digest, sighash, tapleaf_scripts, tweak, rand_aux)
 
     def _sign_input(self, tx_digest: bytes, sighash: int = SIGHASH_ALL) -> str:
         """Signs a transaction input with the private key
@@ -441,6 +442,7 @@ def _sign_taproot_input(
         sighash: int = SIGHASH_ALL,
         scripts: Optional[Script | list[Script] | list[list[Script]]] = None,
         tweak: bool = True,
+        rand_aux: bytes = None,
     ) -> str:
         """Signs a taproot transaction input with the private key
 
@@ -470,7 +472,8 @@ def _sign_taproot_input(
         # it is the hash of the tx_digest and private key
         # TODO not identical to Bitcoin Core's signature, rand_aux
         # needs to change if we want identical signatures!
-        rand_aux = hashlib.sha256(tx_digest + byte_key).digest()
+        if rand_aux is None:
+            rand_aux = hashlib.sha256(tx_digest + byte_key).digest()
 
         # use BIP-340 python's reference implementation for signing
         sig = schnorr_sign(tx_digest, byte_key, rand_aux)
@@ -534,7 +537,7 @@ def __init__(self, hex_str: str = None, message: str = None, signature: bytes =
         ----------
         hex_str : str, optional
             the public key in hex string
-        
+
         In case of generating public key from message and signature:-
         message : str, optional
             The original message that was signed
@@ -611,7 +614,7 @@ def __init__(self, hex_str: str = None, message: str = None, signature: bytes =
         elif message or signature:
             if not message:
                 raise ValueError("Empty message provided for public key recovery.")
-            
+
             if(len(signature) != 65):
                 raise ValueError("Invalid signature length, must be exactly 65 bytes")
 
@@ -620,9 +623,9 @@ def __init__(self, hex_str: str = None, message: str = None, signature: bytes =
             recovery_id = signature[0] - 31
             if not (0 <= recovery_id <= 3): # A valid recovery ID is between 0 and 3
                 raise ValueError(f"Invalid recovery ID: expected 31-34, got {signature[0]}")
-            
+
             signature = signature[1:] #Remove recovery id from signature
-            
+
             # All bitcoin signatures include the magic prefix. It is just a string
             # added to the message to distinguish Bitcoin-specific messages.
             message_magic = add_magic_prefix(message)
@@ -687,7 +690,7 @@ def to_taproot_hex(
         tweak_int = calculate_tweak(self, scripts)
 
         # keep x-only coordinate
-        tweak_and_odd = tweak_taproot_pubkey(self.key.to_string(), tweak_int) 
+        tweak_and_odd = tweak_taproot_pubkey(self.key.to_string(), tweak_int)
         pubkey = tweak_and_odd[0][:32]
         is_odd = tweak_and_odd[1]