From a6e655e80ad93ee7f71fc77b1d0525174399b55c Mon Sep 17 00:00:00 2001
From: callebtc <93376500+callebtc@users.noreply.github.com>
Date: Sun, 2 Oct 2022 12:11:37 +0200
Subject: [PATCH] script

---
 cashu/core/script.py | 138 +++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 138 insertions(+)
 create mode 100644 cashu/core/script.py

diff --git a/cashu/core/script.py b/cashu/core/script.py
new file mode 100644
index 0000000..bdfd728
--- /dev/null
+++ b/cashu/core/script.py
@@ -0,0 +1,138 @@
+import hashlib
+import base64
+
+COIN = 100_000_000
+TXID = "bff785da9f8169f49be92fa95e31f0890c385bfb1bd24d6b94d7900057c617ae"
+
+from bitcoin.core import (
+    lx,
+    COutPoint,
+    CMutableTxOut,
+    CMutableTxIn,
+    CMutableTransaction,
+)
+from bitcoin.core.script import *
+from bitcoin.core.scripteval import VerifyScript
+from bitcoin.wallet import CBitcoinAddress, CBitcoinSecret
+
+
+def step0_carol_privkey():
+    """Private key"""
+    h = hashlib.sha256(b"correct horse battery staple").digest()
+    seckey = CBitcoinSecret.from_secret_bytes(h)
+    return seckey
+
+
+def step0_carolt_checksig_redeemscrip(carol_pubkey):
+    """Create script"""
+    txin_redeemScript = CScript([carol_pubkey, OP_CHECKSIG])
+    # txin_redeemScript = CScript(
+    #     [
+    #         3,
+    #         3,
+    #         OP_LESSTHANOREQUAL,
+    #         OP_VERIFY,
+    #     ]
+    # )
+    return txin_redeemScript
+
+
+def step1_carol_create_p2sh_address(txin_redeemScript):
+    """Create address (serialized scriptPubKey) to share with Alice"""
+    # print("Script:", b2x(txin_redeemScript))
+    # returns [OP_HASH160, bitcointx.core.Hash160(self), OP_EQUAL]
+    txin_scriptPubKey = txin_redeemScript.to_p2sh_scriptPubKey()
+    txin_p2sh_address = CBitcoinAddress.from_scriptPubKey(txin_scriptPubKey)
+    # print("Pay to:", str(txin_p2sh_address))
+    return txin_p2sh_address
+
+
+def step1_bob_carol_create_tx(txin_p2sh_address):
+    """Create transaction"""
+    txid = lx(TXID)
+    vout = 0
+    txin = CMutableTxIn(COutPoint(txid, vout))
+    txout = CMutableTxOut(
+        int(0.0005 * COIN),
+        CBitcoinAddress(str(txin_p2sh_address)).to_scriptPubKey(),
+    )
+    tx = CMutableTransaction([txin], [txout])
+    return tx, txin
+
+
+def step2_carol_sign_tx(txin_redeemScript):
+    """Sign transaction with private key"""
+    seckey = step0_carol_privkey()
+    txin_p2sh_address = step1_carol_create_p2sh_address(txin_redeemScript)
+    tx, txin = step1_bob_carol_create_tx(txin_p2sh_address)
+    sighash = SignatureHash(txin_redeemScript, tx, 0, SIGHASH_ALL)
+    sig = seckey.sign(sighash) + bytes([SIGHASH_ALL])
+    txin.scriptSig = CScript([sig, txin_redeemScript])
+    return txin
+
+
+def step3_bob_verify_script(txin_signature, txin_redeemScript):
+    txin_scriptPubKey = txin_redeemScript.to_p2sh_scriptPubKey()
+
+    try:
+        VerifyScript(txin_signature, txin_scriptPubKey, tx, 0)
+        return True
+    except Exception as e:
+        print(e)
+        return False
+
+
+if __name__ == "__main__":
+    # https://github.com/romanz/python-bitcointx/blob/master/examples/spend-p2sh-txout.py
+    # CAROL shares txin_p2sh_address with ALICE:
+
+    # ---------
+    # CAROL defines scripthash and ALICE mints them
+
+    txin_redeemScript = step0_carolt_checksig_redeemscrip(step0_carol_privkey().pub)
+    txin_p2sh_address = step1_carol_create_p2sh_address(txin_redeemScript)
+    print(f"Carol sends Alice secret = P2SH:{txin_p2sh_address}")
+    print("")
+
+    # ---------
+
+    # ALICE: mint tokens with secret SCRIPT:txin_p2sh_address
+    print(f"Alice mints tokens with secret = P2SH:{txin_p2sh_address}")
+    print("")
+    # ...
+
+    # ---------
+    # CAROL redeems with MINT
+
+    # CAROL PRODUCES txin_redeemScript and txin_signature to send to MINT
+    txin_redeemScript = step0_carolt_checksig_redeemscrip(step0_carol_privkey().pub)
+    txin_signature = step2_carol_sign_tx(txin_redeemScript).scriptSig
+
+    txin_redeemScript_b64 = base64.urlsafe_b64encode(txin_redeemScript).decode()
+    txin_signature_b64 = base64.urlsafe_b64encode(txin_signature).decode()
+    print(
+        f"Carol to Bob:\nscript: {txin_redeemScript_b64}\nsignature: {txin_signature_b64}\n"
+    )
+    print("")
+    # ---------
+    # MINT verifies SCRIPT and SIGNATURE and mints tokens
+
+    # MINT receives txin_redeemScript_b64 and txin_signature_b64 fom CAROL:
+    txin_redeemScript = CScript(base64.urlsafe_b64decode(txin_redeemScript_b64))
+    txin_signature = CScript(base64.urlsafe_b64decode(txin_signature_b64))
+
+    txin_p2sh_address = step1_carol_create_p2sh_address(txin_redeemScript)
+    print(f"Bob recreates secret: P2SH:{txin_p2sh_address}")
+    # MINT checks that SCRIPT:txin_p2sh_address has not been spent yet
+    # ...
+    tx, _ = step1_bob_carol_create_tx(txin_p2sh_address)
+
+    print(
+        f"Bob verifies:\nscript: {txin_redeemScript_b64}\nsignature: {txin_signature_b64}\n"
+    )
+    script_valid = step3_bob_verify_script(txin_signature, txin_redeemScript)
+    # MINT redeems tokens and stores SCRIPT:txin_p2sh_address
+    # ...
+
+    print("Successfull.")
+    # print("Transaction:", b2x(tx.serialize()))