bls.py

#!/usr/bin/python

import bn256

"""
Demonstrate the bn256 module using the BLS short signature scheme
"""

def bls_keygen():
    k,g = bn256.g2_random()
    return (k,g)

def bls_sign(privkey, msg):
    pt = bn256.g1_hash_to_point(msg)
    assert pt.is_on_curve()

    return bn256.g1_compress(pt.scalar_mul(privkey))

def bls_verify(pubkey, msg, csig):
    sig = bn256.g1_uncompress(csig)

    assert type(pubkey) == bn256.curve_twist
    assert type(sig) == bn256.curve_point

    msg_pt = bn256.g1_hash_to_point(msg)

    assert msg_pt.is_on_curve()

    v1 = bn256.optimal_ate(pubkey, msg_pt)
    v2 = bn256.optimal_ate(bn256.twist_G, sig)

    return v1 == v2

def test():
    (priv,pub) = bls_keygen()

    import time

    for i in range(1000):
        msg = ("message @ %f" % time.time()).encode("utf-8")

        print(msg)
        sig = bls_sign(priv, msg)

        print("sig",sig)

        ok = bls_verify(pub, msg, sig)
        assert ok

test()