Secp256k1.py

# https://bitcoin.stackexchange.com/a/59806

def secp256k1(s):
    
    P = 2**256 - 2**32 - 2**9 - 2**8 - 2**7 - 2**6 - 2**4 - 1
    N = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141
    G = (0x79BE667EF9DCBBAC55A06295CE870B07029BFCDB2DCE28D959F2815B16F81798,
         0x483ADA7726A3C4655DA4FBFC0E1108A8FD17B448A68554199C47D08FFB10D4B8)

    def add(p, q):
        px, py = p
        qx, qy = q
        if p == q:
            lam = (3 * pow(px, 2)) * 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 int(s, 16) & (1 << i):
            ret = G if ret == None else add(ret, G)
        G = add(G, G)

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