def test_G2_compress_and_decompress_flags(pt, on_curve, is_infinity):
if on_curve:
z1, z2 = compress_G2(pt)
x1 = z1 % POW_2_381
c_flag1 = (z1 % 2**384) // POW_2_383
b_flag1 = (z1 % POW_2_383) // POW_2_382
a_flag1 = (z1 % POW_2_382) // POW_2_381
x2 = z2 % POW_2_381
c_flag2 = (z2 % 2**384) // POW_2_383
b_flag2 = (z2 % POW_2_383) // POW_2_382
a_flag2 = (z2 % POW_2_382) // POW_2_381
assert x1 < q
assert x2 < q
assert c_flag2 == b_flag2 == a_flag2 == 0
assert c_flag1 == 1
if is_infinity:
assert b_flag1 == 1
assert a_flag1 == x1 == x2 == 0
else:
assert b_flag1 == 0
_, y = normalize(pt)
_, y_im = y.coeffs
# TODO: need a case for y_im == 0
assert a_flag1 == (y_im * 2) // q
# Correct flags should decompress correct x, y
normalize(decompress_G2((z1, z2))) == normalize(pt)
else:
with pytest.raises(ValueError):
compress_G2(pt)
def hash_message(message: bytes, DST: bytes = None) -> bytes:
from hashlib import sha256
from py_ecc.bls.hash import i2osp
from py_ecc.bls.hash_to_curve import hash_to_G2
from py_ecc.bls.point_compression import compress_G2
DST = DST or b'' # TODO: Use a valid DST
mapped_msg = hash_to_G2(message, DST, sha256)
z1, z2 = compress_G2(mapped_msg)
return i2osp(z1, 48) + i2osp(z2, 48)
def OpBLS_Compress_G2(arg):
op = json.loads(arg)
v = to_int(op['g2_v'])
w = to_int(op['g2_w'])
x = to_int(op['g2_x'])
y = to_int(op['g2_y'])
g2 = (FQ2((v, x)), FQ2((w, y)), FQ2.one())
try:
compressed = compress_G2(g2)
except ValueError:
return
point = [str(compressed[0]), str(compressed[1])]
r = json.dumps(point)
return bytes(r, 'utf-8')
assert b_flag1 == 1
assert a_flag1 == x1 == x2 == 0
else:
assert b_flag1 == 0
_, y = normalize(pt)
_, y_im = y.coeffs
# TODO: need a case for y_im == 0
assert a_flag1 == (y_im * 2) // q
# Correct flags should decompress correct x, y
normalize(decompress_G2((z1, z2))) == normalize(pt)
else:
with pytest.raises(ValueError):
compress_G2(pt)
compressed_g2 = compress_G2(G2)
compressed_z2 = compress_G2(Z2)
@pytest.mark.parametrize(
'z, error_message',
[
(compressed_g2, None), # baseline
((compressed_g2[0] & ~(1 << 383), compressed_g2[1]),
"c_flag should be 1"), # set c_flag1 to 0
((compressed_g2[0] | (1 << 382), compressed_g2[1]),
"b_flag should be 0"), # set b_flag1 to 1
((compressed_z2[0] & ~(1 << 382), compressed_z2[1]),
"b_flag should be 1"), # set b_flag1 to 0
((compressed_z2[0] | (1 << 381), compressed_z2[1]),
"a point at infinity should have a_flag == 0"), # set a_flag1 to 1