def test_get_plaintext_tally_all_guardians_present(self, data,
parties: int,
contests: int):
# Arrange
description = data.draw(election_descriptions(parties, contests))
builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS, self.QUORUM,
description)
metadata, context = builder.set_public_key(
self.joint_public_key).build()
plaintext_ballots: List[PlaintextBallot] = data.draw(
plaintext_voted_ballots(metadata, randrange(3, 6)))
plaintext_tallies = accumulate_plaintext_ballots(plaintext_ballots)
encrypted_tally = self._generate_encrypted_tally(
metadata, context, plaintext_ballots)
subject = DecryptionMediator(metadata, context, encrypted_tally)
# act
for guardian in self.guardians:
self.assertIsNotNone(subject.announce(guardian))
decrypted_tallies = subject.get_plaintext_tally()
result = self._convert_to_selections(decrypted_tallies)
# assert
self.assertIsNotNone(result)
self.assertEqual(plaintext_tallies, result)
def generate(self, number_of_ballots: int = DEFAULT_NUMBER_OF_BALLOTS):
"""
Generate the sample data set
"""
rmtree(RESULTS_DIR, ignore_errors=True)
(
public_data,
private_data,
) = self.election_factory.get_hamilton_election_with_encryption_context()
plaintext_ballots = self.ballot_factory.generate_fake_plaintext_ballots_for_election(
public_data.metadata, number_of_ballots
)
self.encrypter = EncryptionMediator(
public_data.metadata, public_data.context, self.encryption_device
)
ciphertext_ballots: List[CiphertextBallot] = []
for plaintext_ballot in plaintext_ballots:
ciphertext_ballots.append(
get_optional(self.encrypter.encrypt(plaintext_ballot))
)
ballot_store = BallotStore()
ballot_box = BallotBox(public_data.metadata, public_data.context, ballot_store)
accepted_ballots: List[CiphertextAcceptedBallot] = []
for ballot in ciphertext_ballots:
if randint(0, 100) % 10 == 0:
accepted_ballots.append(ballot_box.spoil(ballot))
else:
accepted_ballots.append(ballot_box.cast(ballot))
ciphertext_tally = get_optional(
tally_ballots(ballot_store, public_data.metadata, public_data.context)
)
decrypter = DecryptionMediator(
public_data.metadata, public_data.context, ciphertext_tally
)
for guardian in private_data.guardians:
decrypter.announce(guardian)
plaintext_tally = get_optional(decrypter.get_plaintext_tally())
publish(
public_data.description,
public_data.context,
public_data.constants,
accepted_ballots,
ciphertext_tally,
plaintext_tally,
public_data.guardians,
)
publish_private_data(
plaintext_ballots, ciphertext_ballots, private_data.guardians
)
def test_get_plaintext_tally_with_all_guardians_present(
self, values, parties: int, contests: int):
# Arrange
description = values.draw(election_descriptions(parties, contests))
builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS, self.QUORUM,
description)
internal_manifest, context = (builder.set_public_key(
self.joint_public_key.joint_public_key).set_commitment_hash(
self.joint_public_key.commitment_hash).build())
plaintext_ballots: List[PlaintextBallot] = values.draw(
plaintext_voted_ballots(internal_manifest, randrange(3, 6)))
expected_plaintext_tally = accumulate_plaintext_ballots(
plaintext_ballots)
encrypted_tally = self._generate_encrypted_tally(
internal_manifest, context, plaintext_ballots)
mediator = DecryptionMediator(self.decryption_mediator_id, context)
available_guardians = self.guardians
DecryptionHelper.perform_decryption_setup(available_guardians,
mediator, context,
encrypted_tally, [])
# Act
plaintext_tally = mediator.get_plaintext_tally(encrypted_tally)
selections = _convert_to_selections(plaintext_tally)
# Assert
self.assertIsNotNone(plaintext_tally)
self.assertIsNotNone(selections)
self.assertEqual(expected_plaintext_tally, selections)
def test_announce(self):
# Arrange
mediator = DecryptionMediator(
self.decryption_mediator_id,
self.context,
)
guardian = self.guardians[0]
guardian_key = self.guardians[0].share_election_public_key()
tally_share = guardian.compute_tally_share(self.ciphertext_tally,
self.context)
ballot_shares = {}
# Act
mediator.announce(guardian_key, tally_share, ballot_shares)
# Assert
self.assertEqual(len(mediator.get_available_guardians()), 1)
# Act
# Announce again
mediator.announce(guardian_key, tally_share, ballot_shares)
# Assert
# Can only announce once
self.assertEqual(len(mediator.get_available_guardians()), 1)
# Cannot get plaintext tally or spoiled ballots without a quorum
self.assertIsNone(mediator.get_plaintext_tally(self.ciphertext_tally))
self.assertIsNone(
mediator.get_plaintext_ballots(self.ciphertext_ballots))
def test_get_plaintext_tally_all_guardians_present_simple(self):
# Arrange
subject = DecryptionMediator(self.metadata, self.context, self.ciphertext_tally)
# act
for guardian in self.guardians:
self.assertIsNotNone(subject.announce(guardian))
decrypted_tallies = subject.get_plaintext_tally()
result = self._convert_to_selections(decrypted_tallies)
# assert
self.assertIsNotNone(result)
self.assertEqual(self.expected_plaintext_tally, result)
def step_4_decrypt_tally(self) -> None:
"""
Homomorphically combine the selections made on all of the cast ballots
and use the Available Guardians to decrypt the combined tally.
In this way, no individual voter's cast ballot is ever decrypted drectly.
"""
# Generate a Homomorphically Accumulated Tally of the ballots
self.ciphertext_tally = get_optional(
tally_ballots(self.ballot_store, self.metadata, self.context)
)
self._assert_message(
tally_ballots.__qualname__,
f"""
- cast: {self.ciphertext_tally.count()}
- spoiled: {len(self.ciphertext_tally.spoiled_ballots)}
Total: {len(self.ciphertext_tally)}
""",
self.ciphertext_tally is not None,
)
# Configure the Decryption
self.decrypter = DecryptionMediator(
self.metadata, self.context, self.ciphertext_tally
)
# Announce each guardian as present
for guardian in self.guardians:
decryption_share = self.decrypter.announce(guardian)
self._assert_message(
DecryptionMediator.announce.__qualname__,
f"Guardian Present: {guardian.object_id}",
decryption_share is not None,
)
# Get the Plain Text Tally
self.plaintext_tally = get_optional(self.decrypter.get_plaintext_tally())
self._assert_message(
DecryptionMediator.get_plaintext_tally.__qualname__,
"Tally Decrypted",
self.plaintext_tally is not None,
)
# Now, compare the results
self.compare_results()
def test_get_plaintext_with_a_missing_guardian(self):
# Arrange
mediator = DecryptionMediator(
self.decryption_mediator_id,
self.context,
)
available_guardians = self.guardians[0:2]
all_guardian_keys = [
guardian.share_election_public_key() for guardian in self.guardians
]
DecryptionHelper.perform_compensated_decryption_setup(
available_guardians,
all_guardian_keys,
mediator,
self.context,
self.ciphertext_tally,
self.ciphertext_ballots,
)
# Act
plaintext_tally = mediator.get_plaintext_tally(self.ciphertext_tally)
plaintext_ballots = mediator.get_plaintext_ballots(
self.ciphertext_ballots)
# Convert to selections to check for the same tally
selections = _convert_to_selections(plaintext_tally)
# Verify we get the same tally back if we call again
another_plaintext_tally = mediator.get_plaintext_tally(
self.ciphertext_tally)
# Assert
self.assertIsNotNone(plaintext_tally)
self.assertIsNotNone(plaintext_ballots)
self.assertEqual(len(self.ciphertext_ballots), len(plaintext_ballots))
self.assertIsNotNone(selections)
self.assertEqual(self.expected_plaintext_tally, selections)
self.assertEqual(plaintext_tally, another_plaintext_tally)
def test_decrypt_spoiled_ballots_all_guardians_present(self):
# Arrange
# precompute decryption shares for the guardians
first_share = compute_decryption_share(self.guardians[0],
self.ciphertext_tally,
self.context)
second_share = compute_decryption_share(self.guardians[1],
self.ciphertext_tally,
self.context)
third_share = compute_decryption_share(self.guardians[2],
self.ciphertext_tally,
self.context)
shares = {
self.guardians[0].object_id: first_share,
self.guardians[1].object_id: second_share,
self.guardians[2].object_id: third_share,
}
subject = DecryptionMediator(self.metadata, self.context,
self.ciphertext_tally)
# act
result = decrypt_spoiled_ballots(
self.ciphertext_tally.spoiled_ballots,
shares,
self.context.crypto_extended_base_hash,
)
# assert
self.assertIsNotNone(result)
self.assertTrue(self.fake_spoiled_ballot.object_id in result)
spoiled_ballot = result[self.fake_spoiled_ballot.object_id]
for contest in self.fake_spoiled_ballot.contests:
for selection in contest.ballot_selections:
self.assertEqual(
spoiled_ballot[contest.object_id].selections[
selection.object_id].plaintext,
result[self.fake_spoiled_ballot.object_id][
contest.object_id].selections[
selection.object_id].plaintext,
)
def test_announce(self):
# Arrange
subject = DecryptionMediator(self.metadata, self.context,
self.ciphertext_tally)
# act
result = subject.announce(self.guardians[0])
# assert
self.assertIsNotNone(result)
# Can only announce once
self.assertIsNotNone(subject.announce(self.guardians[0]))
# Cannot submit another share internally
self.assertFalse(
subject._submit_decryption_share(
TallyDecryptionShare(self.guardians[0].object_id, ZERO_MOD_P,
{}, {})))
# Cannot get plaintext tally without a quorum
self.assertIsNone(subject.get_plaintext_tally())
def test_get_plaintext_with_all_guardians_present(self):
# Arrange
mediator = DecryptionMediator(
self.decryption_mediator_id,
self.context,
)
available_guardians = self.guardians
DecryptionHelper.perform_decryption_setup(
available_guardians,
mediator,
self.context,
self.ciphertext_tally,
self.ciphertext_ballots,
)
# Act
plaintext_tally = mediator.get_plaintext_tally(self.ciphertext_tally)
plaintext_ballots = mediator.get_plaintext_ballots(
self.ciphertext_ballots)
# Convert to selections to check for the same tally
selections = _convert_to_selections(plaintext_tally)
# Verify we get the same tally back if we call again
another_plaintext_tally = mediator.get_plaintext_tally(
self.ciphertext_tally)
# Assert
self.assertIsNotNone(plaintext_tally)
self.assertIsNotNone(plaintext_ballots)
self.assertEqual(len(self.ciphertext_ballots), len(plaintext_ballots))
self.assertIsNotNone(selections)
self.assertEqual(self.expected_plaintext_tally, selections)
self.assertEqual(plaintext_tally, another_plaintext_tally)
def test_get_plaintext_tally_compensate_missing_guardian_simple(self):
# Arrange
subject = DecryptionMediator(self.metadata, self.context, self.ciphertext_tally)
# Act
self.assertIsNotNone(subject.announce(self.guardians[0]))
self.assertIsNotNone(subject.announce(self.guardians[1]))
# explicitly compensate to demonstrate that this is possible, but not required
self.assertIsNotNone(
subject.compensate(self.guardians[2].object_id, identity_auxiliary_decrypt)
)
decrypted_tallies = subject.get_plaintext_tally()
self.assertIsNotNone(decrypted_tallies)
result = self._convert_to_selections(decrypted_tallies)
# assert
self.assertIsNotNone(result)
print(result)
self.assertEqual(self.expected_plaintext_tally, result)
def step_4_decrypt_tally(self) -> None:
"""
Homomorphically combine the selections made on all of the cast ballots
and use the Available Guardians to decrypt the combined tally.
In this way, no individual voter's cast ballot is ever decrypted drectly.
"""
# Generate a Homomorphically Accumulated Tally of the ballots
self.ciphertext_tally = get_optional(
tally_ballots(self.ballot_store, self.internal_manifest,
self.context))
self.ciphertext_ballots = get_ballots(self.ballot_store,
BallotBoxState.SPOILED)
self._assert_message(
tally_ballots.__qualname__,
f"""
- cast: {self.ciphertext_tally.cast()}
- spoiled: {self.ciphertext_tally.spoiled()}
Total: {len(self.ciphertext_tally)}
""",
self.ciphertext_tally is not None,
)
# Configure the Decryption
ciphertext_ballots = list(self.ciphertext_ballots.values())
self.decryption_mediator = DecryptionMediator(
"decryption-mediator",
self.context,
)
# Announce each guardian as present
count = 0
for guardian in self.guardians:
guardian_key = guardian.share_election_public_key()
tally_share = guardian.compute_tally_share(self.ciphertext_tally,
self.context)
ballot_shares = guardian.compute_ballot_shares(
ciphertext_ballots, self.context)
self.decryption_mediator.announce(guardian_key, tally_share,
ballot_shares)
count += 1
self._assert_message(
DecryptionMediator.announce.__qualname__,
f"Guardian Present: {guardian.id}",
len(self.decryption_mediator.get_available_guardians()) ==
count,
)
# Get the plaintext Tally
self.plaintext_tally = get_optional(
self.decryption_mediator.get_plaintext_tally(
self.ciphertext_tally))
self._assert_message(
DecryptionMediator.get_plaintext_tally.__qualname__,
"Tally Decrypted",
self.plaintext_tally is not None,
)
# Get the plaintext Spoiled Ballots
self.plaintext_spoiled_ballots = get_optional(
self.decryption_mediator.get_plaintext_ballots(ciphertext_ballots))
self._assert_message(
DecryptionMediator.get_plaintext_ballots.__qualname__,
"Spoiled Ballots Decrypted",
self.plaintext_tally is not None,
)
# Now, compare the results
self.compare_results()
def generate(
self,
number_of_ballots: int = DEFAULT_NUMBER_OF_BALLOTS,
cast_spoil_ratio: int = CAST_SPOIL_RATIO,
):
"""
Generate the sample data set
"""
# Clear the results directory
rmtree(RESULTS_DIR, ignore_errors=True)
# Configure the election
(
public_data,
private_data,
) = self.election_factory.get_hamilton_election_with_encryption_context(
)
plaintext_ballots = self.ballot_factory.generate_fake_plaintext_ballots_for_election(
public_data.metadata, number_of_ballots)
self.encrypter = EncryptionMediator(public_data.metadata,
public_data.context,
self.encryption_device)
# Encrypt some ballots
ciphertext_ballots: List[CiphertextBallot] = []
for plaintext_ballot in plaintext_ballots:
ciphertext_ballots.append(
get_optional(self.encrypter.encrypt(plaintext_ballot)))
ballot_store = BallotStore()
ballot_box = BallotBox(public_data.metadata, public_data.context,
ballot_store)
# Randomly cast/spoil the ballots
accepted_ballots: List[CiphertextAcceptedBallot] = []
for ballot in ciphertext_ballots:
if randint(0, 100) % cast_spoil_ratio == 0:
accepted_ballots.append(ballot_box.spoil(ballot))
else:
accepted_ballots.append(ballot_box.cast(ballot))
# Tally
ciphertext_tally = get_optional(
tally_ballots(ballot_store, public_data.metadata,
public_data.context))
# Decrypt
decrypter = DecryptionMediator(public_data.metadata,
public_data.context, ciphertext_tally)
for i, guardian in enumerate(private_data.guardians):
if i < QUORUM or not THRESHOLD_ONLY:
decrypter.announce(guardian)
plaintext_tally = get_optional(decrypter.get_plaintext_tally())
# Publish
publish(
public_data.description,
public_data.context,
public_data.constants,
[self.encryption_device],
accepted_ballots,
ciphertext_tally.spoiled_ballots.values(),
publish_ciphertext_tally(ciphertext_tally),
plaintext_tally,
public_data.guardians,
)
publish_private_data(plaintext_ballots, ciphertext_ballots,
private_data.guardians)
def generate(
self,
number_of_ballots: int = DEFAULT_NUMBER_OF_BALLOTS,
spoil_rate: int = DEFAULT_SPOIL_RATE,
use_all_guardians: bool = DEFAULT_USE_ALL_GUARDIANS,
):
"""
Generate the sample data set
"""
# Clear the results directory
rmtree(RESULTS_DIR, ignore_errors=True)
# Configure the election
(
manifest,
private_data,
) = self.election_factory.get_hamilton_manifest_with_encryption_context()
plaintext_ballots = (
self.ballot_factory.generate_fake_plaintext_ballots_for_election(
manifest.internal_manifest, number_of_ballots
)
)
self.encrypter = EncryptionMediator(
manifest.internal_manifest, manifest.context, self.encryption_device
)
# Encrypt some ballots
ciphertext_ballots: List[CiphertextBallot] = []
for plaintext_ballot in plaintext_ballots:
ciphertext_ballots.append(
get_optional(self.encrypter.encrypt(plaintext_ballot))
)
ballot_store = DataStore()
ballot_box = BallotBox(
manifest.internal_manifest, manifest.context, ballot_store
)
# Randomly cast/spoil the ballots
submitted_ballots: List[SubmittedBallot] = []
for ballot in ciphertext_ballots:
if randint(0, 100) < spoil_rate:
submitted_ballots.append(ballot_box.spoil(ballot))
else:
submitted_ballots.append(ballot_box.cast(ballot))
# Tally
spoiled_ciphertext_ballots = get_ballots(ballot_store, BallotBoxState.SPOILED)
ciphertext_tally = get_optional(
tally_ballots(ballot_store, manifest.internal_manifest, manifest.context)
)
# Decrypt
mediator = DecryptionMediator("sample-manifest-decrypter", manifest.context)
available_guardians = (
private_data.guardians
if use_all_guardians
else private_data.guardians[0:QUORUM]
)
DecryptionHelper.perform_decryption_setup(
available_guardians,
mediator,
manifest.context,
ciphertext_tally,
spoiled_ciphertext_ballots,
)
plaintext_tally = get_optional(mediator.get_plaintext_tally(ciphertext_tally))
plaintext_spoiled_ballots = get_optional(
mediator.get_plaintext_ballots(spoiled_ciphertext_ballots)
)
# Publish
publish(
manifest.manifest,
manifest.context,
manifest.constants,
[self.encryption_device],
submitted_ballots,
plaintext_spoiled_ballots.values(),
ciphertext_tally.publish(),
plaintext_tally,
manifest.guardians,
)
publish_private_data(
plaintext_ballots, ciphertext_ballots, private_data.guardians
)