---

# Тест: GF(2^128) с R = 0x87 << 120
R = 0x87 << 120
MASK = (1 << 128) - 1

def gf_mul(x, y):
    z = 0
    v = x & MASK
    for i in range(128):
        if (y >> i) & 1:
            z ^= v
        msb = (v >> 127) & 1
        v = (v << 1) & MASK
        if msb:
            v ^= R
    return z & MASK

def gf_inv(x):
    result = 1
    base = x
    exp = (1 << 128) - 2
    while exp:
        if exp & 1:
            result = gf_mul(result, base)
        base = gf_mul(base, base)
        exp >>= 1
    return result

print("=== GF(2^128) с R = 0x87 << 120 ===")
for t in [1, 2, 3, 0x80, 0x123456789abcdef0123456789abcdef0]:
    inv_t = gf_inv(t)
    p = gf_mul(t, inv_t)
    print(f"inv({t:032x}) * {t:032x} = {p:032x} {'OK' if p == 1 else 'FAIL'}")