Blind chain signature verification
- also adds serialisation, deserialisation and optional metadata
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77
src/pyelliptic/blindchain.py
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77
src/pyelliptic/blindchain.py
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@ -0,0 +1,77 @@
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"""
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Blind signature chain with a top level CA
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"""
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from eccblind import ECCBlind
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try:
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import msgpack
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except ImportError:
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try:
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import umsgpack as msgpack
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except ImportError:
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import fallback.umsgpack.umsgpack as msgpack
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from eccblind import ECCBlind
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def encode_datetime(obj):
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"""
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Method to format time
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"""
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return {'Time': int(obj.strftime("%s"))}
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class ECCBlindChain(object): # pylint: disable=too-many-instance-attributes
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"""
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# Class for ECC Blind Chain signature functionality
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"""
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chain = []
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ca = []
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def __init__(self, chain=None):
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if chain is not None:
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self.chain = chain
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def serialize(self):
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data = msgpack.packb(self.chain)
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return data
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@staticmethod
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def deserialize(self, chain):
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"""
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Deserialize the data using msgpack
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"""
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data = msgpack.unpackb(chain)
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return ECCBlindChain(data)
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def add_level(self, pubkey, metadata, signature):
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self.chain.append((pubkey, metadata, signature))
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def add_ca(self, ca):
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pubkey, metadata = ECCBlind.deserialize(ca)
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self.ca.append(pubkey)
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def verify(self, msg, value):
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lastpubkey = None
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retval = False
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for level in reversed(self.chain):
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pubkey, metadata, signature = level
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verifier_obj = ECCBlind(pubkey=pubkey, metadata)
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if not lastpubkey:
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retval = verifier_obj.verify(msg, signature, value)
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else:
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retval = verifier_obj.verify(lastpubkey, signature, value)
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if not reval:
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break
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lastpubkey = pubkey
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if retval:
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retval = False
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for ca in self.ca:
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match = True
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for i in range(4):
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if lastpubkey[i] != ca[i]:
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match = False
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break
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if match:
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return True
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return retval
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@ -10,9 +10,52 @@ http://www.isecure-journal.com/article_39171_47f9ec605dd3918c2793565ec21fcd7a.pd
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# variable names are based on the math in the paper, so they don't conform
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# to PEP8
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from hashlib import sha256
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import time
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try:
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import msgpack
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except ImportError:
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try:
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import umsgpack as msgpack
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except ImportError:
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import fallback.umsgpack.umsgpack as msgpack
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from .openssl import OpenSSL
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class Metadata(object):
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"""
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Pubkey metadata
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"""
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def __init__(self, exp=0, value=0):
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self.exp = 0
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self.value = 0
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if exp:
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self.exp = exp
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if value:
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self.value = value
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def serialize(self):
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if self.exp or self.value:
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return [self.exp, self.value]
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else:
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return []
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@staticmethod
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def deserialize(self, data):
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exp, value = data
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return Medatadata(exp, value)
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def verify(self, value):
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if self.value and value > self.value:
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return False
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if self.exp:
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if time.time() > self.exp:
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return False
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return True
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class ECCBlind(object): # pylint: disable=too-many-instance-attributes
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"""
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Class for ECC blind signature functionality
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@ -75,7 +118,21 @@ class ECCBlind(object): # pylint: disable=too-many-instance-attributes
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OpenSSL.EC_POINT_get_affine_coordinates_GFp(group, F, x0, y0, ctx)
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return x0
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def __init__(self, curve="secp256k1", pubkey=None):
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@staticmethod
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def deserialize(self, data):
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pubkey_deserialized, meta = msgpack.unpackb(data)
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if meta:
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obj = ECCBlind(pubkey=pubkey_deserialized, metadata=meta)
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else:
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obj = ECCBlind(pubkey=pubkey_deserialized)
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return obj
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def serialize(self):
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data = (self.pubkey, self.metadata.serialize)
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retval = msgpack.packb(data)
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return retval
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def __init__(self, curve="secp256k1", pubkey=None, metadata=None):
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self.ctx = OpenSSL.BN_CTX_new()
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if pubkey:
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@ -101,6 +158,14 @@ class ECCBlind(object): # pylint: disable=too-many-instance-attributes
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self.iO = OpenSSL.EC_POINT_new(self.group)
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OpenSSL.EC_POINT_set_to_infinity(self.group, self.iO)
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if metadata:
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self._set_metadata(self, metadata)
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else:
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self.metadata = Metadata()
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def _set_metadata(self, metadata):
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self.metadata = Metadata.deserialise(metadata)
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def signer_init(self):
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"""
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Init signer
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@ -119,6 +184,7 @@ class ECCBlind(object): # pylint: disable=too-many-instance-attributes
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Requester creates a new signing request
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"""
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self.R = R
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msghash = sha256(msg)
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# Requester: 3 random blinding factors
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self.F = OpenSSL.EC_POINT_new(self.group)
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@ -151,7 +217,7 @@ class ECCBlind(object): # pylint: disable=too-many-instance-attributes
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# Requester: Blinding (m' = br(m) + a)
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self.m = OpenSSL.BN_new()
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OpenSSL.BN_bin2bn(msg, len(msg), self.m)
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OpenSSL.BN_bin2bn(msghash, len(msghash), self.m)
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self.m_ = OpenSSL.BN_new()
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OpenSSL.BN_mod_mul(self.m_, self.b, self.r, self.n, self.ctx)
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@ -180,14 +246,15 @@ class ECCBlind(object): # pylint: disable=too-many-instance-attributes
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self.signature = (s, self.F)
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return self.signature
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def verify(self, msg, signature):
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def verify(self, msg, signature, value=0):
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"""
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Verify signature with certifier's pubkey
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"""
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# convert msg to BIGNUM
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self.m = OpenSSL.BN_new()
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OpenSSL.BN_bin2bn(msg, len(msg), self.m)
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msghash = sha256(msg)
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OpenSSL.BN_bin2bn(msghash, len(msghash), self.m)
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# init
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s, self.F = signature
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@ -206,5 +273,8 @@ class ECCBlind(object): # pylint: disable=too-many-instance-attributes
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retval = OpenSSL.EC_POINT_cmp(self.group, lhs, rhs, self.ctx)
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if retval == -1:
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raise RuntimeError("EC_POINT_cmp returned an error")
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else:
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return retval == 0
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elif retval != 0:
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return False
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elif self.metadata:
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return self.metadata.verify(value)
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return True
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@ -2,10 +2,12 @@
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Test for ECC blind signatures
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"""
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import os
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import time
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import unittest
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from ctypes import cast, c_char_p
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from pybitmessage.pyelliptic.eccblind import ECCBlind
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from pybitmessage.pyelliptic.eccblind import ECCBlind, Metadata
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from pybitmessage.pyelliptic.eccblindchain import ECCBlindChain
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from pybitmessage.pyelliptic.openssl import OpenSSL
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@ -50,3 +52,47 @@ class TestBlindSig(unittest.TestCase):
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# (5) Verification
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verifier_obj = ECCBlind(pubkey=signer_obj.pubkey)
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self.assertTrue(verifier_obj.verify(msg, signature))
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# Serialization and deserialisation
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pk = signer_obj.serialize()
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pko = ECCBlind.deserialize(pk)
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self.assertTrue(pko.verify(msg, signature))
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def test_blind_sig_chain(self):
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"""Test blind signature chain using a random certifier key and a random message"""
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test_levels = 5
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value = 1
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msg = os.urandom(1024)
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chain = ECCBlindChain()
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ca = ECCBlind()
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signer_obj = ca
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signer_pubkey = signer_obj.serialize()
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for level in range(test_levels):
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if level == 0:
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metadata = Metadata(exp=int(time.time()) + 100,
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value=value).serialize()
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requester_obj = ECCBlind(pubkey=signer_obj.pubkey,
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metadata=metadata)
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else:
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requester_obj = ECCBlind(pubkey=signer_obj.pubkey)
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point_r = signer_obj.signer_init()
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if level == test_levels - 1:
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msg_blinded = requester_obj.create_signing_request(point_r,
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msg)
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else:
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msg_blinded = requester.obj.create_signing_request(point_r,
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signer_pubkey)
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signature_blinded = signer_obj.blind_sign(msg_blinded)
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signature = requester_obj.unblind(signature_blinded)
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chain.add_level(signer_obj.pubkey,
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signer_obj.metadata.serialize,
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signature)
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signer_obj = requester_obj
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signer_pubkey = requester_obj.serialize()
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sigchain = chain.serialize()
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verifychain = ECCBlindChain.deserialize(sigchain)
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self.assertTrue(verifychain.verify(msg, value))
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