def test_encrypt_selection_valid_input_tampered_encryption_fails(
self,
selection_description: Tuple[str, SelectionDescription],
keypair: ElGamalKeyPair,
seed: ElementModQ,
random_seed: int,
):
# Arrange
_, description = selection_description
random = Random(random_seed)
subject = ballot_factory.get_random_selection_from(description, random)
# Act
result = encrypt_selection(
subject,
description,
keypair.public_key,
ONE_MOD_Q,
seed,
should_verify_proofs=False,
)
self.assertTrue(
result.is_valid_encryption(description.crypto_hash(),
keypair.public_key, ONE_MOD_Q))
# tamper with the encryption
malformed_encryption = deepcopy(result)
malformed_message = malformed_encryption.ciphertext._replace(
pad=mult_p(result.ciphertext.pad, TWO_MOD_P))
malformed_encryption.ciphertext = malformed_message
# tamper with the proof
malformed_proof = deepcopy(result)
altered_a0 = mult_p(result.proof.proof_zero_pad, TWO_MOD_P)
malformed_disjunctive = DisjunctiveChaumPedersenProof(
altered_a0,
malformed_proof.proof.proof_zero_data,
malformed_proof.proof.proof_one_pad,
malformed_proof.proof.proof_one_data,
malformed_proof.proof.proof_zero_challenge,
malformed_proof.proof.proof_one_challenge,
malformed_proof.proof.challenge,
malformed_proof.proof.proof_zero_response,
malformed_proof.proof.proof_one_response,
)
malformed_proof.proof = malformed_disjunctive
# Assert
self.assertFalse(
malformed_encryption.is_valid_encryption(description.crypto_hash(),
keypair.public_key,
ONE_MOD_Q))
self.assertFalse(
malformed_proof.is_valid_encryption(description.crypto_hash(),
keypair.public_key, ONE_MOD_Q))
def test_decrypt_selection_valid_input_tampered_fails(
self,
selection_description: Tuple[str, SelectionDescription],
keypair: ElGamalKeyPair,
seed: ElementModQ,
random_seed: int,
):
# Arrange
_, description = selection_description
random = Random(random_seed)
data = ballot_factory.get_random_selection_from(description, random)
# Act
subject = encrypt_selection(data, description, keypair.public_key,
seed)
# tamper with the encryption
malformed_encryption = deepcopy(subject)
malformed_message = malformed_encryption.ciphertext._replace(
pad=mult_p(subject.ciphertext.pad, TWO_MOD_P))
malformed_encryption.ciphertext = malformed_message
# tamper with the proof
malformed_proof = deepcopy(subject)
altered_a0 = mult_p(subject.proof.a0, TWO_MOD_P)
malformed_disjunctive = DisjunctiveChaumPedersenProof(
altered_a0,
malformed_proof.proof.b0,
malformed_proof.proof.a1,
malformed_proof.proof.b1,
malformed_proof.proof.c0,
malformed_proof.proof.c1,
malformed_proof.proof.v0,
malformed_proof.proof.v1,
)
malformed_proof.proof = malformed_disjunctive
result_from_key_malformed_encryption = decrypt_selection_with_secret(
malformed_encryption, description, keypair.public_key,
keypair.secret_key)
result_from_key_malformed_proof = decrypt_selection_with_secret(
malformed_proof, description, keypair.public_key,
keypair.secret_key)
result_from_nonce_malformed_encryption = decrypt_selection_with_nonce(
malformed_encryption, description, keypair.public_key)
result_from_nonce_malformed_proof = decrypt_selection_with_nonce(
malformed_proof, description, keypair.public_key)
# Assert
self.assertIsNone(result_from_key_malformed_encryption)
self.assertIsNone(result_from_key_malformed_proof)
self.assertIsNone(result_from_nonce_malformed_encryption)
self.assertIsNone(result_from_nonce_malformed_proof)