Generación de dirección MultiSig N-of-M

multisig.py

from binascii import a2b_hex
from hashlib import new
from collections import deque
from os import urandom
from argparse import ArgumentParser

# opcode
OP_CHECKMULTISIG = 'ae'

# Arguments
p = ArgumentParser(description='Creación de dirección MultiSig N-of-M')
p.add_argument('N', help='N: Firmas necesarias', type=int)
p.add_argument('M', help='M: Número de llaves privadas a generar', type=int)
args = p.parse_args()

# SHA256(SHA256(string))
def doubleSHA256(s):
    return new('sha256', new('sha256', a2b_hex(s)).digest()).hexdigest()

# RIPEMD160(SHA256(string))
def hash160(s):
    return new('ripemd160', new('sha256', a2b_hex(s)).digest()).hexdigest()

# https://github.com/joeblackwaslike/base58chec
def b58check(val):
    charset = b'123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz'
    output = b''
    p, acc = 1, 0

    base = len(charset)

    if base == 58:
        pad_len = len(val)
        val = val.lstrip(b'\0')
        pad_len -= len(val)

        for char in deque(reversed(val)):
            acc += p * char
            p = p << 8

        while acc:
            acc, idx = divmod(acc, base)
            output = charset[idx:idx+1] + output

        prefix = bytes([charset[0]]) * pad_len
        return prefix + output

# https://bitcoin.stackexchange.com/a/59806
def secp256k1(s):
    G = (55066263022277343669578718895168534326250603453777594175500187360389116729240,
         32670510020758816978083085130507043184471273380659243275938904335757337482424)
    N = 115792089237316195423570985008687907852837564279074904382605163141518161494337
    P = 2**256 - 2**32 - 2**9 - 2**8 - 2**7 - 2**6 - 2**4 - 1

    sk = int(s, 16)

    def add(p, q):
        px, py = p
        qx, qy = q
        if p == q:
            lam = (3 * px * px) * pow(2 * py, P - 2, P)
        else:
            lam = (qy - py) * pow(qx - px, P - 2, P)
        rx = lam**2 - px - qx
        ry = lam * (px - rx) - py
        return rx % P, ry % P

    ret = None
    for i in range(256):
        if sk & (1 << i):
            if ret is None:
                ret = G
            else:
                ret = add(ret, G)
        G = add(G, G)

    return '04' + '{:064x}'.format(ret[0]) + '{:064x}'.format(ret[1])

# create opcode OP_1 to OP_16
def get_OP(n):
    if 0 < n <= 16:
        return hex(80 + n)[2:]

# create opcode OP_PUSHDATA
def get_hexlen(string):
    # fixed-length hex(len(string))
    return '{:02x}'.format(int(len(string)/2))

# P2SH address
def get_P2SH_addr(s):
    # Chaucha SCRIPT_PREFIX = 50 (0x32)
    p2sh_prefix = '32'

    # base58check(prefix + sha160(redeemscript) + checksum)
    scripthash = hash160(s)
    checksum = doubleSHA256(p2sh_prefix + scripthash)[:8]
    p2sh_addr = b58check(a2b_hex(p2sh_prefix + scripthash + checksum))
    return p2sh_addr.decode('utf-8')

def main():
    # N of M multisig Address
    N = args.N
    M = args.M
    print('> GENERATING %s-TO-%s MULTISIG ADDRESS !!' % (N, M))

    # create private keys
    privkeys = []
    for i in range(M):
        privkey = new('sha256', urandom(N*M*i)).hexdigest()
        privkeys.append(privkey)

    # get P2SH redeem script
    # (OP_N + OP_PUSHDATA + <pubkeys> + OP_M + OP_CHECKMULTISIG)
    redeemScript = get_OP(N)
    for i in privkeys:
        pubkey = secp256k1(i)
        redeemScript += get_hexlen(pubkey) + pubkey
    redeemScript += get_OP(M) + OP_CHECKMULTISIG

    # get P2SH address
    addr = get_P2SH_addr(redeemScript)

    # logger
    print('> MULTISIG ADDRESS: %s' % addr)
    print('> REDEEM SCRIPT: %s' % redeemScript)
    for i in range(len(privkeys)):
        print('> PRIVKEY #%i: %s' % (i+1, privkeys[i]))

if __name__ == '__main__':
    main()