def gen_ec_keypair(curve="secp112r1"):
# this function generates EC key pair
try:
curve = OpenSSL.curves[curve]
key = OpenSSL.EC_KEY_new_by_curve_name(curve)
OpenSSL.EC_KEY_generate_key(key)
_pubkey_x = OpenSSL.BN_new()
_pubkey_y = OpenSSL.BN_new()
_privkey = OpenSSL.EC_KEY_get0_private_key(key)
_pubkey = OpenSSL.EC_KEY_get0_public_key(key)
_group = OpenSSL.EC_KEY_get0_group(key)
OpenSSL.EC_POINT_get_affine_coordinates_GFp(_group, _pubkey, _pubkey_x, _pubkey_y, 0)
privkey = OpenSSL.malloc(0, OpenSSL.BN_num_bytes(_privkey))
pubkeyx = OpenSSL.malloc(0, OpenSSL.BN_num_bytes(_pubkey_x))
pubkeyy = OpenSSL.malloc(0, OpenSSL.BN_num_bytes(_pubkey_y))
OpenSSL.BN_bn2bin(_privkey, privkey)
privkey = privkey.raw
OpenSSL.BN_bn2bin(_pubkey_x, pubkeyx)
pubkeyx = pubkeyx.raw
OpenSSL.BN_bn2bin(_pubkey_y, pubkeyy)
pubkeyy = pubkeyy.raw
# self.raw_check_key(privkey, pubkeyx, pubkeyy)
full_privkey = pack("!H", curve) + pack("!H", len(privkey)) + privkey
full_pubkey = pack("!H", curve) + pack("!H", len(pubkeyx)) + pubkeyx + pack("!H", len(pubkeyy)) + pubkeyy
return full_privkey, full_pubkey
finally:
# release c pointers
OpenSSL.EC_KEY_free(key)
OpenSSL.BN_free(_pubkey_x)
OpenSSL.BN_free(_pubkey_y)
def ecdh_key(a_privkey, b_pubkey):
# keys should be in binary format
a_curve = int(a_privkey[0:2].encode("hex"), 16)
b_curve = int(b_pubkey[0:2].encode("hex"), 16)
if a_curve != b_curve:
raise Exception("ECDH Error: Both key must have the save curve type.")
sx = int(b_pubkey[2:4].encode("hex"), 16)
sy = int(b_pubkey[4 + sx : sx + 6].encode("hex"), 16)
pub_x, pub_y = b_pubkey[4 : 4 + sx], b_pubkey[6 + sx : 6 + sx + sy]
b_key = OpenSSL.EC_KEY_new_by_curve_name(b_curve)
_pub_x = OpenSSL.BN_bin2bn(pub_x, sx, 0)
_pub_y = OpenSSL.BN_bin2bn(pub_y, sy, 0)
_group = OpenSSL.EC_KEY_get0_group(b_key)
_pubkey = OpenSSL.EC_POINT_new(_group)
OpenSSL.EC_POINT_set_affine_coordinates_GFp(_group, _pubkey, _pub_x, _pub_y, 0)
OpenSSL.EC_KEY_set_public_key(b_key, _pubkey)
# OpenSSL.EC_KEY_check_key(b_key)
s = int(a_privkey[2:4].encode("hex"), 16)
priv = a_privkey[4 : 4 + s]
a_key = OpenSSL.EC_KEY_new_by_curve_name(a_curve)
_privkey = OpenSSL.BN_bin2bn(priv, len(priv), 0)
OpenSSL.EC_KEY_set_private_key(a_key, _privkey)
# ECDH
OpenSSL.ECDH_set_method(a_key, OpenSSL.ECDH_OpenSSL())
ecdh_buf = OpenSSL.malloc(0, s) # computed buffer size should the same as key length
ecdh_keylen = OpenSSL.ECDH_compute_key(ecdh_buf, s, _pubkey, a_key, 0)
return ecdh_buf.raw