def test_cheating_ursula_sends_garbage(N, M):
priv_key_alice = keys.UmbralPrivateKey.gen_key()
pub_key_alice = priv_key_alice.get_pubkey()
# Bob
priv_key_bob = keys.UmbralPrivateKey.gen_key()
pub_key_bob = priv_key_bob.get_pubkey()
sym_key, capsule_alice = pre._encapsulate(pub_key_alice.point_key)
kfrags = pre.split_rekey(priv_key_alice, pub_key_bob, M, N)
cfrags, challenges, metadata = [], [], []
for i, kfrag in enumerate(kfrags[:M]):
cfrag = pre.reencrypt(kfrag, capsule_alice)
# Example of potential metadata to describe the challenge request
metadata_i = {
'ursula_id': i,
'timestamp': time.time(),
'capsule': bytes(capsule_alice),
'cfrag': bytes(cfrag)
}
metadata_i = str(metadata_i).encode()
metadata.append(metadata_i)
challenge = pre._challenge(kfrag, capsule_alice, cfrag, metadata_i)
capsule_alice.attach_cfrag(cfrag)
assert pre._check_challenge(capsule_alice, cfrag, challenge,
pub_key_alice.point_key,
pub_key_bob.point_key, metadata_i)
cfrags.append(cfrag)
challenges.append(challenge)
# Let's put random garbage in one of the cfrags
cfrags[0].point_eph_e1 = Point.gen_rand()
cfrags[0].point_eph_v1 = Point.gen_rand()
capsule_alice._reconstruct_shamirs_secret(pub_key_alice,
priv_key_bob) # activate capsule
with pytest.raises(pre.GenericUmbralError):
sym_key2 = pre._decapsulate_reencrypted(pub_key_bob.point_key,
priv_key_bob.bn_key,
pub_key_alice.point_key,
capsule_alice)
assert not pre._check_challenge(capsule_alice, cfrags[0], challenges[0],
pub_key_alice.point_key,
pub_key_bob.point_key, metadata[0])
# The response of cheating Ursula is in capsules[0],
# so the rest of challenges chould be correct:
for i, challenge in enumerate(challenges[1:], 1):
cfrag = cfrags[i]
assert pre._check_challenge(capsule_alice, cfrag, challenge,
pub_key_alice.point_key,
pub_key_bob.point_key, metadata[i])
def test_cheating_ursula_replays_old_reencryption(N, M):
priv_key_alice = keys.UmbralPrivateKey.gen_key()
pub_key_alice = priv_key_alice.get_pubkey()
priv_key_bob = keys.UmbralPrivateKey.gen_key()
pub_key_bob = priv_key_bob.get_pubkey()
sym_key_alice1, capsule_alice1 = pre._encapsulate(pub_key_alice.point_key)
sym_key_alice2, capsule_alice2 = pre._encapsulate(pub_key_alice.point_key)
kfrags = pre.split_rekey(priv_key_alice, pub_key_bob, M, N)
cfrags, challenges = [], []
for index, kfrag in enumerate(kfrags):
if index == 0:
# Let's put the re-encryption of a different Alice ciphertext
cfrag = pre.reencrypt(kfrag, capsule_alice2)
else:
cfrag = pre.reencrypt(kfrag, capsule_alice1)
metadata = ("Challenge metadata: index {}".format(index)).encode()
challenge = pre._challenge(kfrag, capsule_alice1, cfrag, metadata)
capsule_alice1.attach_cfrag(cfrag)
challenges.append(challenge)
cfrags.append(cfrag)
# Let's activate the capsule
capsule_alice1._reconstruct_shamirs_secret(pub_key_alice, priv_key_bob)
with pytest.raises(pre.GenericUmbralError):
sym_key = pre._decapsulate_reencrypted(pub_key_bob.point_key,
priv_key_bob.bn_key,
pub_key_alice.point_key,
capsule_alice1)
metadata = b"Challenge metadata: index 0"
assert not pre._check_challenge(capsule_alice1,
cfrags[0],
challenges[0],
pub_key_alice.point_key,
pub_key_bob.point_key,
metadata
)
# The response of cheating Ursula is in capsules[0],
# so the rest of challenges chould be correct:
for i, challenge in enumerate(challenges[1:], 1):
cfrag = cfrags[i]
metadata = ("Challenge metadata: index {}".format(i)).encode()
assert pre._check_challenge(capsule_alice1,
cfrag,
challenge,
pub_key_alice.point_key,
pub_key_bob.point_key,
metadata
)
def test_cheating_ursula_replays_old_reencryption(N, M):
priv_key_alice = keys.UmbralPrivateKey.gen_key()
pub_key_alice = priv_key_alice.get_pubkey()
priv_key_bob = keys.UmbralPrivateKey.gen_key()
pub_key_bob = priv_key_bob.get_pubkey()
sym_key_alice1, capsule_alice1 = pre._encapsulate(pub_key_alice.point_key)
sym_key_alice2, capsule_alice2 = pre._encapsulate(pub_key_alice.point_key)
kfrags = pre.split_rekey(priv_key_alice, pub_key_bob, M, N)
cfrags, challenges, metadata = [], [], []
for i, kfrag in enumerate(kfrags):
if i == 0:
# Let's put the re-encryption of a different Alice ciphertext
cfrag = pre.reencrypt(kfrag, capsule_alice2)
else:
cfrag = pre.reencrypt(kfrag, capsule_alice1)
# Example of potential metadata to describe the challenge request
metadata_i = {
'ursula_id': i,
'timestamp': time.time(),
'capsule': bytes(capsule_alice1),
'cfrag': bytes(cfrag)
}
metadata.append(str(metadata_i).encode())
challenge = pre._challenge(kfrag, capsule_alice1, cfrag, metadata[i])
capsule_alice1.attach_cfrag(cfrag)
challenges.append(challenge)
cfrags.append(cfrag)
# Let's activate the capsule
capsule_alice1._reconstruct_shamirs_secret(pub_key_alice, priv_key_bob)
with pytest.raises(pre.GenericUmbralError):
sym_key = pre._decapsulate_reencrypted(pub_key_bob.point_key,
priv_key_bob.bn_key,
pub_key_alice.point_key,
capsule_alice1)
assert not pre._check_challenge(capsule_alice1, cfrags[0], challenges[0],
pub_key_alice.point_key,
pub_key_bob.point_key, metadata[0])
# The response of cheating Ursula is in capsules[0],
# so the rest of challenges should be correct:
for i, challenge in enumerate(challenges[1:], 1):
cfrag = cfrags[i]
assert pre._check_challenge(capsule_alice1, cfrag, challenge,
pub_key_alice.point_key,
pub_key_bob.point_key, metadata[i])
def test_m_of_n(N, M, alices_keys, bobs_keys):
priv_key_alice, pub_key_alice = alices_keys
priv_key_bob, pub_key_bob = bobs_keys
sym_key, capsule = pre._encapsulate(pub_key_alice.point_key)
kfrags = pre.split_rekey(priv_key_alice, pub_key_bob, M, N)
for kfrag in kfrags:
assert kfrag.verify(pub_key_alice.point_key, pub_key_bob.point_key)
for i, kfrag in enumerate(kfrags[:M]):
cfrag = pre.reencrypt(kfrag, capsule)
capsule.attach_cfrag(cfrag)
metadata = ("Challenge metadata: index {}".format(i)).encode()
ch = pre._challenge(kfrag, capsule, cfrag, metadata)
assert pre._check_challenge(capsule,
cfrag,
ch,
pub_key_alice.point_key,
pub_key_bob.point_key,
metadata
)
# assert capsule.is_openable_by_bob() # TODO: Is it possible to check here if >= m cFrags have been attached?
# capsule.open(pub_bob, priv_bob, pub_alice)
capsule._reconstruct_shamirs_secret(pub_key_alice, priv_key_bob)
sym_key_from_capsule = pre._decapsulate_reencrypted(pub_key_bob.point_key,
priv_key_bob.bn_key,
pub_key_alice.point_key,
capsule)
assert sym_key == sym_key_from_capsule
def test_m_of_n(N, M, alices_keys, bobs_keys):
priv_key_alice, pub_key_alice = alices_keys
priv_key_bob, pub_key_bob = bobs_keys
sym_key, capsule = pre._encapsulate(pub_key_alice.point_key)
kfrags = pre.split_rekey(priv_key_alice, pub_key_bob, M, N)
for kfrag in kfrags:
assert kfrag.verify(pub_key_alice.point_key, pub_key_bob.point_key)
for i, kfrag in enumerate(kfrags[:M]):
cfrag = pre.reencrypt(kfrag, capsule)
capsule.attach_cfrag(cfrag)
# Example of potential metadata to describe the challenge request
metadata = {
'ursula_id': i,
'timestamp': time.time(),
'capsule': bytes(capsule),
'cfrag': bytes(cfrag)
}
metadata = str(metadata).encode()
ch = pre._challenge(kfrag, capsule, cfrag, metadata)
assert pre._check_challenge(capsule, cfrag, ch,
pub_key_alice.point_key,
pub_key_bob.point_key, metadata)
# assert capsule.is_openable_by_bob() # TODO: Is it possible to check here if >= m cFrags have been attached?
# capsule.open(pub_bob, priv_bob, pub_alice)
capsule._reconstruct_shamirs_secret(pub_key_alice, priv_key_bob)
sym_key_from_capsule = pre._decapsulate_reencrypted(
pub_key_bob.point_key, priv_key_bob.bn_key, pub_key_alice.point_key,
capsule)
assert sym_key == sym_key_from_capsule
def test_cheating_ursula_sends_garbage(N, M):
priv_key_alice = keys.UmbralPrivateKey.gen_key()
pub_key_alice = priv_key_alice.get_pubkey()
# Bob
priv_key_bob = keys.UmbralPrivateKey.gen_key()
pub_key_bob = priv_key_bob.get_pubkey()
sym_key, capsule_alice = pre._encapsulate(pub_key_alice.point_key)
kfrags = pre.split_rekey(priv_key_alice, pub_key_bob, M, N)
cfrags, challenges = [], []
for i, kfrag in enumerate(kfrags[:M]):
cfrag = pre.reencrypt(kfrag, capsule_alice)
metadata = ("Challenge metadata: index {}".format(i)).encode()
challenge = pre._challenge(kfrag, capsule_alice, cfrag, metadata)
capsule_alice.attach_cfrag(cfrag)
assert pre._check_challenge(capsule_alice,
cfrag,
challenge,
pub_key_alice.point_key,
pub_key_bob.point_key,
metadata
)
cfrags.append(cfrag)
challenges.append(challenge)
# Let's put random garbage in one of the cfrags
cfrags[0].point_eph_e1 = Point.gen_rand()
cfrags[0].point_eph_v1 = Point.gen_rand()
capsule_alice._reconstruct_shamirs_secret(pub_key_alice, priv_key_bob) # activate capsule
with pytest.raises(pre.GenericUmbralError):
sym_key2 = pre._decapsulate_reencrypted(pub_key_bob.point_key,
priv_key_bob.bn_key,
pub_key_alice.point_key,
capsule_alice)
metadata = b"Challenge metadata: index 0"
assert not pre._check_challenge(capsule_alice,
cfrags[0],
challenges[0],
pub_key_alice.point_key,
pub_key_bob.point_key,
metadata
)
# The response of cheating Ursula is in capsules[0],
# so the rest of challenges chould be correct:
for i, challenge in enumerate(challenges[1:], 1):
cfrag = cfrags[i]
metadata = ("Challenge metadata: index {}".format(i)).encode()
assert pre._check_challenge(capsule_alice,
cfrag,
challenge,
pub_key_alice.point_key,
pub_key_bob.point_key,
metadata
)