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Message for validating KFrag is now bytes of constituents instead of a BigNum. Fixes #148.

pull/145/head
jMyles 2018-05-25 14:41:13 -07:00
parent 90240be847
commit 8394cf6e44
3 changed files with 19 additions and 30 deletions
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16
umbral/_pre.py
View File

@ -73,21 +73,14 @@ def assess_cfrag_correctness(cfrag,
if cfrag.proof.metadata is not None:
hash_input += (cfrag.proof.metadata,)
h = CurveBN.hash(*hash_input, params=params)
kfrag_signature = cfrag.proof.kfrag_signature
########
ni = cfrag._point_noninteractive
xcoord = cfrag._point_xcoord
kfrag_id = cfrag._kfrag_id
g = params.g
signature_input = (kfrag_id, pubkey_a_deleg_point, pubkey_b_point, u1, ni, xcoord)
kfrag_signed_message = CurveBN.hash(*signature_input, params=params)
valid_kfrag_signature = cfrag.proof.kfrag_signature.verify(kfrag_signed_message.to_bytes(),
pubkey_a_sig)
kfrag_validity_message = bytes().join(bytes(material) for material in (kfrag_id, pubkey_a_deleg_point, pubkey_b_point, u1, ni, xcoord))
valid_kfrag_signature = cfrag.proof.kfrag_signature.verify(kfrag_validity_message, pubkey_a_sig)
z3 = cfrag.proof.bn_sig
correct_reencryption_of_e = z3 * e == e2 + (h * e1)
@ -121,8 +114,7 @@ def verify_kfrag(kfrag,
#  We check that the commitment u1 is well-formed
correct_commitment = u1 == key * u
signature_input = (id, pubkey_a_deleg_point, pubkey_b_point, u1, ni, xcoord)
message = CurveBN.hash(*signature_input, params=params)
valid_kfrag_signature = kfrag.signature.verify(message.to_bytes(), pubkey_a_sig)
kfrag_validity_message = bytes().join(bytes(material) for material in (kfrag_id, pubkey_a_deleg_point, pubkey_b_point, u1, ni, xcoord))
valid_kfrag_signature = kfrag.signature.verify(kfrag_validity_message, pubkey_a_sig)
return correct_commitment & valid_kfrag_signature

3
umbral/point.py
View File

@ -224,6 +224,9 @@ class Point(object):
backend.openssl_assert(res == 1)
return Point(inv, self.curve_nid, self.group)
def __bytes__(self):
return self.to_bytes()
def unsafe_hash_to_point(data, params, label=None):
"""

30
umbral/pre.py
View File

@ -14,10 +14,7 @@ from umbral.keys import UmbralPrivateKey, UmbralPublicKey
from umbral.params import UmbralParameters
from umbral.point import Point
from umbral.signing import Signer
from umbral.utils import poly_eval, lambda_coeff, kdf, get_curve_keysize_bytes
from io import BytesIO
from umbral.utils import poly_eval, lambda_coeff, kdf
import os
CHACHA20_KEY_SIZE = 32
@ -64,7 +61,7 @@ class Capsule(object):
self._attached_cfrags = list()
@classmethod
def get_size(cls, curve: ec.EllipticCurve=None, activated=False):
def get_size(cls, curve: ec.EllipticCurve = None, activated=False):
"""
Returns the size (in bytes) of a Capsule given the curve.
If no curve is provided, it will use the default curve.
@ -94,24 +91,23 @@ class Capsule(object):
if len(capsule_bytes) == cls.get_size(curve, activated=True):
splitter = BytestringSplitter(
(Point, point_size), # point_e
(Point, point_size), # point_v
(Point, point_size), # point_e
(Point, point_size), # point_v
(CurveBN, bn_size), # bn_sig
(Point, point_size), # point_e_prime
(Point, point_size), # point_v_prime
(Point, point_size), # point_e_prime
(Point, point_size), # point_v_prime
(Point, point_size) # point_noninteractive
)
else:
splitter = BytestringSplitter(
(Point, point_size), # point_e
(Point, point_size), # point_v
(CurveBN, bn_size) # bn_sig
(Point, point_size), # point_e
(Point, point_size), # point_v
(CurveBN, bn_size) # bn_sig
)
components = splitter(capsule_bytes)
return cls(*components)
def _original_to_bytes(self) -> bytes:
return bytes().join(c.to_bytes() for c in self.original_components())
@ -291,11 +287,9 @@ def split_rekey(privkey_a_bn: Union[UmbralPrivateKey, CurveBN],
u1 = rk * u
# TODO: change this Schnorr signature for Ed25519 or ECDSA (#97)
signature_input = (id, pubkey_a_point, pubkey_b_point, u1, ni, xcoord)
z1 = CurveBN.hash(*signature_input, params=params)
signature = signer_a(z1.to_bytes())
kfrag_validity_message = bytes().join(
bytes(material) for material in (id, pubkey_a_point, pubkey_b_point, u1, ni, xcoord))
signature = signer_a(kfrag_validity_message)
kfrag = KFrag(id=id, bn_key=rk,
point_noninteractive=ni, point_commitment=u1,