def test_encrypt_simple_ballot_from_files_succeeds(self):
# Arrange
keypair = elgamal_keypair_from_secret(int_to_q(2))
election = election_factory.get_simple_election_from_file()
metadata, context = election_factory.get_fake_ciphertext_election(
election, keypair.public_key
)
data = ballot_factory.get_simple_ballot_from_file()
self.assertTrue(data.is_valid(metadata.ballot_styles[0].object_id))
device = EncryptionDevice("Location")
subject = EncryptionMediator(metadata, context, device)
# Act
result = subject.encrypt(data)
# Assert
self.assertIsNotNone(result)
self.assertEqual(data.object_id, result.object_id)
self.assertTrue(
result.is_valid_encryption(
metadata.description_hash,
keypair.public_key,
context.crypto_extended_base_hash,
)
)
def test_encrypt_ballot_with_stateful_composer_succeeds(self):
# Arrange
keypair = elgamal_keypair_from_secret(int_to_q(2))
manifest = election_factory.get_fake_manifest()
internal_manifest, context = election_factory.get_fake_ciphertext_election(
manifest, keypair.public_key)
data = election_factory.get_fake_ballot(internal_manifest)
self.assertTrue(
data.is_valid(internal_manifest.ballot_styles[0].object_id))
device = election_factory.get_encryption_device()
subject = EncryptionMediator(internal_manifest, context, device)
# Act
result = subject.encrypt(data)
# Assert
self.assertIsNotNone(result)
self.assertTrue(
result.is_valid_encryption(
internal_manifest.manifest_hash,
keypair.public_key,
context.crypto_extended_base_hash,
))
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 step_2_encrypt_votes(self) -> None:
"""
Using the `CiphertextElectionContext` encrypt ballots for the election
"""
# Configure the Encryption Device
self.device = ElectionFactory.get_encryption_device()
self.encrypter = EncryptionMediator(self.internal_manifest,
self.context, self.device)
self._assert_message(
EncryptionDevice.__qualname__,
f"Ready to encrypt at location: {self.device.location}",
)
# Load some Ballots
self.plaintext_ballots = BallotFactory().get_simple_ballots_from_file()
self._assert_message(
PlaintextBallot.__qualname__,
f"Loaded ballots: {len(self.plaintext_ballots)}",
len(self.plaintext_ballots) > 0,
)
# Encrypt the Ballots
for plaintext_ballot in self.plaintext_ballots:
encrypted_ballot = self.encrypter.encrypt(plaintext_ballot)
self._assert_message(
EncryptionMediator.encrypt.__qualname__,
f"Ballot Id: {plaintext_ballot.object_id}",
encrypted_ballot is not None,
)
self.ciphertext_ballots.append(get_optional(encrypted_ballot))
def test_decrypt_ballot_valid_input_missing_nonce_fails(
self, keypair: ElGamalKeyPair
):
# Arrange
election = election_factory.get_simple_election_from_file()
metadata, context = election_factory.get_fake_ciphertext_election(
election, keypair.public_key
)
data = ballot_factory.get_simple_ballot_from_file()
device = EncryptionDevice("Location")
operator = EncryptionMediator(metadata, context, device)
# Act
subject = operator.encrypt(data)
self.assertIsNotNone(subject)
subject.nonce = None
missing_nonce_value = None
result_from_nonce = decrypt_ballot_with_nonce(
subject, metadata, context.crypto_extended_base_hash, keypair.public_key,
)
result_from_nonce_seed = decrypt_ballot_with_nonce(
subject,
metadata,
context.crypto_extended_base_hash,
keypair.public_key,
missing_nonce_value,
)
# Assert
self.assertIsNone(result_from_nonce)
self.assertIsNone(result_from_nonce_seed)
def test_decrypt_ballot_valid_input_missing_nonce_fails(
self, keypair: ElGamalKeyPair
):
# Arrange
election = election_factory.get_simple_manifest_from_file()
internal_manifest, context = election_factory.get_fake_ciphertext_election(
election, keypair.public_key
)
data = ballot_factory.get_simple_ballot_from_file()
device = election_factory.get_encryption_device()
operator = EncryptionMediator(internal_manifest, context, device)
# Act
subject = operator.encrypt(data)
self.assertIsNotNone(subject)
subject.nonce = None
missing_nonce_value = None
result_from_nonce = decrypt_ballot_with_nonce(
subject,
internal_manifest,
context.crypto_extended_base_hash,
keypair.public_key,
)
# SUGGEST this test is the same as the one above
result_from_nonce_seed = decrypt_ballot_with_nonce(
subject,
internal_manifest,
context.crypto_extended_base_hash,
keypair.public_key,
missing_nonce_value,
)
# Assert
self.assertIsNone(result_from_nonce)
self.assertIsNone(result_from_nonce_seed)
def encrypt(ballot_as_dict: dict,
encrypter: EncryptionMediator) -> CiphertextBallot:
"""
The ballot gets encrypted and stored in the ballots_encrypted field for the
cast/spoil decision later.
:param encrypter:
:param ballot_as_dict:
:return:
"""
ballot: PlaintextBallot = ballot_from_json(ballot_as_dict)
# Encrypt the ballot
encrypted_ballot: CiphertextBallot = encrypter.encrypt(ballot)
return encrypted_ballot
def create() -> Tuple:
"""
An election with only one guardian and random keys gets generated.
More configuration options and the ability to hold a key ceremony should be added later.
"""
# Open an election manifest file
with open(os.path.join(ELECTION_MANIFEST), "r") as manifest:
string_representation = manifest.read()
election_description = ElectionDescription.from_json(
string_representation)
# Create an election builder instance, and configure it for a single public-private keypair.
# in a real election, you would configure this for a group of guardians. See Key Ceremony for more information.
# TODO: Allow real key ceremony
builder = ElectionBuilder(
number_of_guardians=
1, # since we will generate a single public-private keypair, we set this to 1
quorum=
1, # since we will generate a single public-private keypair, we set this to 1
description=election_description)
# We simply generate a random keypair. For a real election this step should
# be replaced by the key ceremony
keypair = elgamal_keypair_random()
builder.set_public_key(keypair.public_key)
# get an `InternalElectionDescription` and `CiphertextElectionContext`
# that are used for the remainder of the election.
(metadata, context) = builder.build()
# Configure an encryption device
# In the docs the encrypter device gets defined when encrypting a ballot.
# I think for our usecase it makes more sense to define one encrypter and use for the whole election
device = EncryptionDevice("polling-place-one")
encrypter = EncryptionMediator(metadata, context, device)
store = BallotStore()
ballot_box = BallotBox(metadata, context, store)
return metadata, context, encrypter, ballot_box, store, keypair
class TestEndToEndElection(TestCase):
"""
Test a complete simple example of executing an End-to-End encrypted election.
In a real world scenario all of these steps would not be completed on the same machine.
"""
NUMBER_OF_GUARDIANS = 5
QUORUM = 3
REMOVE_OUTPUT = False
# Step 0 - Configure Election
description: ElectionDescription
election_builder: ElectionBuilder
metadata: InternalElectionDescription
context: CiphertextElectionContext
constants: ElectionConstants
# Step 1 - Key Ceremony
mediator: KeyCeremonyMediator
guardians: List[Guardian] = []
coefficient_validation_sets: List[CoefficientValidationSet] = []
# Step 2 - Encrypt Votes
device: EncryptionDevice
encrypter: EncryptionMediator
plaintext_ballots: List[PlaintextBallot]
ciphertext_ballots: List[CiphertextBallot] = []
# Step 3 - Cast and Spoil
ballot_store: BallotStore
ballot_box: BallotBox
# Step 4 - Decrypt Tally
ciphertext_tally: CiphertextTally
plaintext_tally: PlaintextTally
decrypter: DecryptionMediator
def test_end_to_end_election(self) -> None:
"""
Execute the simplified end-to-end test demonstrating each component of the system.
"""
self.step_0_configure_election()
self.step_1_key_ceremony()
self.step_2_encrypt_votes()
self.step_3_cast_and_spoil()
self.step_4_decrypt_tally()
self.step_5_publish_and_verify()
def step_0_configure_election(self) -> None:
"""
To conduct an election, load an `ElectionDescription` file
"""
# Load a pre-configured Election Description
# TODO: replace with complex election
self.description = ElectionFactory().get_simple_election_from_file()
print(f"""
{'-'*40}\n
# Election Summary:
# Scope: {self.description.election_scope_id}
# Geopolitical Units: {len(self.description.geopolitical_units)}
# Parties: {len(self.description.parties)}
# Candidates: {len(self.description.candidates)}
# Contests: {len(self.description.contests)}
# Ballot Styles: {len(self.description.ballot_styles)}\n
{'-'*40}\n
""")
self._assert_message(
ElectionDescription.is_valid.__qualname__,
"Verify that the input election meta-data is well-formed",
self.description.is_valid(),
)
# Create an Election Builder
self.election_builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS,
self.QUORUM, self.description)
self._assert_message(
ElectionBuilder.__qualname__,
f"Created with number_of_guardians: {self.NUMBER_OF_GUARDIANS} quorum: {self.QUORUM}",
)
# Move on to the Key Ceremony
def step_1_key_ceremony(self) -> None:
"""
Using the NUMBER_OF_GUARDIANS, generate public-private keypairs and share
representations of those keys with QUORUM of other Guardians. Then, combine
the public election keys to make a joint election key that is used to encrypt ballots
"""
# Setup Guardians
for i in range(self.NUMBER_OF_GUARDIANS):
self.guardians.append(
Guardian("guardian_" + str(i), i, self.NUMBER_OF_GUARDIANS,
self.QUORUM))
# Setup Mediator
self.mediator = KeyCeremonyMediator(self.guardians[0].ceremony_details)
# Attendance (Public Key Share)
for guardian in self.guardians:
self.mediator.announce(guardian)
self._assert_message(
KeyCeremonyMediator.all_guardians_in_attendance.__qualname__,
"Confirms all guardians have shared their public keys",
self.mediator.all_guardians_in_attendance(),
)
# Run the Key Ceremony process,
# Which shares the keys among the guardians
orchestrated = self.mediator.orchestrate()
self._assert_message(
KeyCeremonyMediator.orchestrate.__qualname__,
"Executes the key exchange between guardians",
orchestrated is not None,
)
self._assert_message(
KeyCeremonyMediator.all_election_partial_key_backups_available.
__qualname__,
"Confirm sall guardians have shared their partial key backups",
self.mediator.all_election_partial_key_backups_available(),
)
# Verification
verified = self.mediator.verify()
self._assert_message(
KeyCeremonyMediator.verify.__qualname__,
"Confirms all guardians truthfully executed the ceremony",
verified,
)
self._assert_message(
KeyCeremonyMediator.
all_election_partial_key_verifications_received.__qualname__,
"Confirms all guardians have submitted a verification of the backups of all other guardians",
self.mediator.all_election_partial_key_verifications_received(),
)
self._assert_message(
KeyCeremonyMediator.all_election_partial_key_backups_verified.
__qualname__,
"Confirms all guardians have verified the backups of all other guardians",
self.mediator.all_election_partial_key_backups_verified(),
)
# Joint Key
joint_key = self.mediator.publish_joint_key()
self._assert_message(
KeyCeremonyMediator.publish_joint_key.__qualname__,
"Publishes the Joint Election Key",
joint_key is not None,
)
# Save Validation Keys
for guardian in self.guardians:
self.coefficient_validation_sets.append(
guardian.share_coefficient_validation_set())
# Build the Election
self.election_builder.set_public_key(get_optional(joint_key))
self.metadata, self.context = get_optional(
self.election_builder.build())
self.constants = ElectionConstants()
# Move on to encrypting ballots
def step_2_encrypt_votes(self) -> None:
"""
Using the `CiphertextElectionContext` encrypt ballots for the election
"""
# Configure the Encryption Device
self.device = EncryptionDevice("polling-place-one")
self.encrypter = EncryptionMediator(self.metadata, self.context,
self.device)
self._assert_message(
EncryptionDevice.__qualname__,
f"Ready to encrypt at location: {self.device.location}",
)
# Load some Ballots
self.plaintext_ballots = BallotFactory().get_simple_ballots_from_file()
self._assert_message(
PlaintextBallot.__qualname__,
f"Loaded ballots: {len(self.plaintext_ballots)}",
len(self.plaintext_ballots) > 0,
)
# Encrypt the Ballots
for plaintext_ballot in self.plaintext_ballots:
encrypted_ballot = self.encrypter.encrypt(plaintext_ballot)
self._assert_message(
EncryptionMediator.encrypt.__qualname__,
f"Ballot Id: {plaintext_ballot.object_id}",
encrypted_ballot is not None,
)
self.ciphertext_ballots.append(get_optional(encrypted_ballot))
# Next, we cast or spoil the ballots
def step_3_cast_and_spoil(self) -> None:
"""
Accept each ballot by marking it as either cast or spoiled.
This example demonstrates one way to accept ballots using the `BallotBox` class
"""
# Configure the Ballot Box
self.ballot_store = BallotStore()
self.ballot_box = BallotBox(self.metadata, self.context,
self.ballot_store)
# Randomly cast or spoil the ballots
for ballot in self.ciphertext_ballots:
# if randint(0, 1):
# accepted_ballot = self.ballot_box.cast(ballot)
# else:
# accepted_ballot = self.ballot_box.spoil(ballot)
accepted_ballot = self.ballot_box.cast(ballot)
self._assert_message(
BallotBox.__qualname__,
f"Accepted Ballot Id: {ballot.object_id} state: {get_optional(accepted_ballot).state}",
accepted_ballot is not None,
)
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 compare_results(self) -> None:
"""
Compare the results to ensure the decryption was done correctly
"""
print(f"""
{'-'*40}
# Election Results:
""")
# Create a representation of each contest's tally
selection_ids = [
selection.object_id for contest in self.metadata.contests
for selection in contest.ballot_selections
]
expected_plaintext_tally: Dict[str, int] = {
key: 0
for key in selection_ids
}
# Tally the expected values from the loaded ballots
for ballot in self.plaintext_ballots:
if (get_optional(self.ballot_store.get(
ballot.object_id)).state == BallotBoxState.CAST):
for contest in ballot.contests:
for selection in contest.ballot_selections:
expected_plaintext_tally[
selection.object_id] += selection.to_int()
# Compare the expected tally to the decrypted tally
for tally_contest in self.plaintext_tally.contests.values():
print(f" Contest: {tally_contest.object_id}")
for tally_selection in tally_contest.selections.values():
expected = expected_plaintext_tally[tally_selection.object_id]
self._assert_message(
f" - Selection: {tally_selection.object_id}",
f"expected: {expected}, actual: {tally_selection.tally}",
expected == tally_selection.tally,
)
print(f"\n{'-'*40}\n")
# Compare the expected values for each spoiled ballot
for ballot_id, accepted_ballot in self.ciphertext_tally.spoiled_ballots.items(
):
if accepted_ballot.state == BallotBoxState.SPOILED:
for plaintext_ballot in self.plaintext_ballots:
if ballot_id == plaintext_ballot.object_id:
print(f"\nSpoiled Ballot: {ballot_id}")
for contest in plaintext_ballot.contests:
print(f"\n Contest: {contest.object_id}")
for selection in contest.ballot_selections:
expected = selection.to_int()
decrypted_selection = (
self.plaintext_tally.spoiled_ballots[
ballot_id][contest.object_id].
selections[selection.object_id])
self._assert_message(
f" - Selection: {selection.object_id}",
f"expected: {expected}, actual: {decrypted_selection.tally}",
expected == decrypted_selection.tally,
)
def step_5_publish_and_verify(self) -> None:
"""Publish and verify steps of the election"""
self.publish_results()
self.verify_results()
if self.REMOVE_OUTPUT:
rmtree(RESULTS_DIR)
def publish_results(self) -> None:
"""
Publish results/artifacts of the election
"""
publish(
self.description,
self.context,
self.constants,
[self.device],
self.ballot_store.all(),
self.ciphertext_tally.spoiled_ballots.values(),
publish_ciphertext_tally(self.ciphertext_tally),
self.plaintext_tally,
self.coefficient_validation_sets,
)
self._assert_message(
"Publish",
f"Artifacts published to: {RESULTS_DIR}",
path.exists(RESULTS_DIR),
)
def verify_results(self) -> None:
"""Verify results of election"""
# Deserialize
description_from_file = ElectionDescription.from_json_file(
DESCRIPTION_FILE_NAME, RESULTS_DIR)
self.assertEqual(self.description, description_from_file)
context_from_file = CiphertextElectionContext.from_json_file(
CONTEXT_FILE_NAME, RESULTS_DIR)
self.assertEqual(self.context, context_from_file)
constants_from_file = ElectionConstants.from_json_file(
CONSTANTS_FILE_NAME, RESULTS_DIR)
self.assertEqual(self.constants, constants_from_file)
device_name = DEVICE_PREFIX + str(self.device.uuid)
device_from_file = EncryptionDevice.from_json_file(
device_name, DEVICES_DIR)
self.assertEqual(self.device, device_from_file)
ciphertext_ballots: List[CiphertextAcceptedBallot] = []
for ballot in self.ballot_store.all():
ballot_name = BALLOT_PREFIX + ballot.object_id
ballot_from_file = CiphertextAcceptedBallot.from_json_file(
ballot_name, BALLOTS_DIR)
self.assertEqual(ballot, ballot_from_file)
spoiled_ballots: List[CiphertextAcceptedBallot] = []
for spoiled_ballot in self.ciphertext_tally.spoiled_ballots.values():
ballot_name = BALLOT_PREFIX + spoiled_ballot.object_id
spoiled_ballot_from_file = CiphertextAcceptedBallot.from_json_file(
ballot_name, SPOILED_DIR)
self.assertEqual(spoiled_ballot, spoiled_ballot_from_file)
ciphertext_tally_from_file = PublishedCiphertextTally.from_json_file(
ENCRYPTED_TALLY_FILE_NAME, RESULTS_DIR)
self.assertEqual(publish_ciphertext_tally(self.ciphertext_tally),
ciphertext_tally_from_file)
plainttext_tally_from_file = PlaintextTally.from_json_file(
TALLY_FILE_NAME, RESULTS_DIR)
self.assertEqual(self.plaintext_tally, plainttext_tally_from_file)
coefficient_validation_sets: List[CoefficientValidationSet] = []
for coefficient_validation_set in self.coefficient_validation_sets:
set_name = COEFFICIENT_PREFIX + coefficient_validation_set.owner_id
coefficient_validation_set_from_file = (
CoefficientValidationSet.from_json_file(
set_name, COEFFICIENTS_DIR))
self.assertEqual(coefficient_validation_set,
coefficient_validation_set_from_file)
def _assert_message(self,
name: str,
message: str,
condition: Union[Callable, bool] = True) -> None:
if callable(condition):
result = condition()
else:
result = condition
print(f"{name}: {message}: {result}")
self.assertTrue(result)
def test_decrypt_ballot_valid_input_succeeds(self, keypair: ElGamalKeyPair):
"""
Check that decryption works as expected by encrypting a ballot using the stateful `EncryptionMediator`
and then calling the various decrypt functions.
"""
# TODO: Hypothesis test instead
# Arrange
election = election_factory.get_simple_election_from_file()
metadata, context = election_factory.get_fake_ciphertext_election(
election, keypair.public_key
)
data = ballot_factory.get_simple_ballot_from_file()
device = EncryptionDevice("Location")
operator = EncryptionMediator(metadata, context, device)
# Act
subject = operator.encrypt(data)
self.assertIsNotNone(subject)
result_from_key = decrypt_ballot_with_secret(
subject,
metadata,
context.crypto_extended_base_hash,
keypair.public_key,
keypair.secret_key,
remove_placeholders=False,
)
result_from_nonce = decrypt_ballot_with_nonce(
subject,
metadata,
context.crypto_extended_base_hash,
keypair.public_key,
remove_placeholders=False,
)
result_from_nonce_seed = decrypt_ballot_with_nonce(
subject,
metadata,
context.crypto_extended_base_hash,
keypair.public_key,
subject.nonce,
remove_placeholders=False,
)
# Assert
self.assertIsNotNone(result_from_key)
self.assertIsNotNone(result_from_nonce)
self.assertIsNotNone(result_from_nonce_seed)
self.assertEqual(data.object_id, subject.object_id)
self.assertEqual(data.object_id, result_from_key.object_id)
self.assertEqual(data.object_id, result_from_nonce.object_id)
self.assertEqual(data.object_id, result_from_nonce_seed.object_id)
for description in metadata.get_contests_for(data.ballot_style):
expected_entries = (
len(description.ballot_selections) + description.number_elected
)
key_contest = [
contest
for contest in result_from_key.contests
if contest.object_id == description.object_id
][0]
nonce_contest = [
contest
for contest in result_from_nonce.contests
if contest.object_id == description.object_id
][0]
seed_contest = [
contest
for contest in result_from_nonce_seed.contests
if contest.object_id == description.object_id
][0]
# Contests may not be voted on the ballot
data_contest_exists = [
contest
for contest in data.contests
if contest.object_id == description.object_id
]
if any(data_contest_exists):
data_contest = data_contest_exists[0]
else:
data_contest = None
self.assertTrue(
key_contest.is_valid(
description.object_id,
expected_entries,
description.number_elected,
description.votes_allowed,
)
)
self.assertTrue(
nonce_contest.is_valid(
description.object_id,
expected_entries,
description.number_elected,
description.votes_allowed,
)
)
self.assertTrue(
seed_contest.is_valid(
description.object_id,
expected_entries,
description.number_elected,
description.votes_allowed,
)
)
for selection_description in description.ballot_selections:
key_selection = [
selection
for selection in key_contest.ballot_selections
if selection.object_id == selection_description.object_id
][0]
nonce_selection = [
selection
for selection in nonce_contest.ballot_selections
if selection.object_id == selection_description.object_id
][0]
seed_selection = [
selection
for selection in seed_contest.ballot_selections
if selection.object_id == selection_description.object_id
][0]
# Selections may be undervoted for a specific contest
if any(data_contest_exists):
data_selection_exists = [
selection
for selection in data_contest.ballot_selections
if selection.object_id == selection_description.object_id
]
else:
data_selection_exists = []
if any(data_selection_exists):
data_selection = data_selection_exists[0]
self.assertTrue(data_selection.to_int() == key_selection.to_int())
self.assertTrue(data_selection.to_int() == nonce_selection.to_int())
self.assertTrue(data_selection.to_int() == seed_selection.to_int())
else:
data_selection = None
# TODO: also check edge cases such as:
# - placeholder selections are true for under votes
self.assertTrue(key_selection.is_valid(selection_description.object_id))
self.assertTrue(
nonce_selection.is_valid(selection_description.object_id)
)
self.assertTrue(
seed_selection.is_valid(selection_description.object_id)
)
def test_encrypt_ballot_with_derivative_nonces_regenerates_valid_proofs(
self, keypair: ElGamalKeyPair):
"""
This test verifies that we can regenerate the contest and selection proofs from the cached nonce values
"""
# TODO: Hypothesis test instead
# Arrange
election = election_factory.get_simple_election_from_file()
metadata, context = election_factory.get_fake_ciphertext_election(
election, keypair.public_key)
data = ballot_factory.get_simple_ballot_from_file()
self.assertTrue(data.is_valid(metadata.ballot_styles[0].object_id))
device = EncryptionDevice("Location")
subject = EncryptionMediator(metadata, context, device)
# Act
result = subject.encrypt(data)
self.assertTrue(
result.is_valid_encryption(context.crypto_extended_base_hash,
keypair.public_key))
# Assert
for contest in result.contests:
# Find the contest description
contest_description = list(
filter(lambda i: i.object_id == contest.object_id,
metadata.contests))[0]
# Homomorpically accumulate the selection encryptions
elgamal_accumulation = elgamal_add(
*
[selection.message for selection in contest.ballot_selections])
# accumulate the selection nonce's
aggregate_nonce = add_q(
*[selection.nonce for selection in contest.ballot_selections])
regenerated_constant = make_constant_chaum_pedersen(
elgamal_accumulation,
contest_description.number_elected,
aggregate_nonce,
keypair.public_key,
add_q(contest.nonce, TWO_MOD_Q),
)
self.assertTrue(
regenerated_constant.is_valid(elgamal_accumulation,
keypair.public_key))
for selection in contest.ballot_selections:
# Since we know the nonce, we can decrypt the plaintext
representation = selection.message.decrypt_known_nonce(
keypair.public_key, selection.nonce)
# one could also decrypt with the secret key:
# representation = selection.message.decrypt(keypair.secret_key)
regenerated_disjuctive = make_disjunctive_chaum_pedersen(
selection.message,
selection.nonce,
keypair.public_key,
add_q(selection.nonce, TWO_MOD_Q),
representation,
)
self.assertTrue(
regenerated_disjuctive.is_valid(selection.message,
keypair.public_key))
class TestEndToEndElection(TestCase):
"""
Test a complete simple example of executing an End-to-End encrypted election.
In a real world scenario all of these steps would not be completed on the same machine.
"""
NUMBER_OF_GUARDIANS = 5
QUORUM = 3
REMOVE_OUTPUT = False
# Step 0 - Configure Election
manifest: Manifest
election_builder: ElectionBuilder
internal_manifest: InternalManifest
context: CiphertextElectionContext
constants: ElectionConstants
# Step 1 - Key Ceremony
mediator: KeyCeremonyMediator
guardians: List[Guardian] = []
# Step 2 - Encrypt Votes
device: EncryptionDevice
encrypter: EncryptionMediator
plaintext_ballots: List[PlaintextBallot]
ciphertext_ballots: List[CiphertextBallot] = []
# Step 3 - Cast and Spoil
ballot_store: DataStore
ballot_box: BallotBox
# Step 4 - Decrypt Tally
ciphertext_tally: CiphertextTally
plaintext_tally: PlaintextTally
plaintext_spoiled_ballots: Dict[str, PlaintextTally]
decryption_mediator: DecryptionMediator
# Step 5 - Publish
guardian_records: List[GuardianRecord] = []
def test_end_to_end_election(self) -> None:
"""
Execute the simplified end-to-end test demonstrating each component of the system.
"""
self.step_0_configure_election()
self.step_1_key_ceremony()
self.step_2_encrypt_votes()
self.step_3_cast_and_spoil()
self.step_4_decrypt_tally()
self.step_5_publish_and_verify()
def step_0_configure_election(self) -> None:
"""
To conduct an election, load an `Manifest` file
"""
# Load a pre-configured Election Description
# TODO: replace with complex election
self.manifest = ElectionFactory().get_simple_manifest_from_file()
print(f"""
{'-'*40}\n
# Election Summary:
# Scope: {self.manifest.election_scope_id}
# Geopolitical Units: {len(self.manifest.geopolitical_units)}
# Parties: {len(self.manifest.parties)}
# Candidates: {len(self.manifest.candidates)}
# Contests: {len(self.manifest.contests)}
# Ballot Styles: {len(self.manifest.ballot_styles)}\n
{'-'*40}\n
""")
self._assert_message(
Manifest.is_valid.__qualname__,
"Verify that the input election meta-data is well-formed",
self.manifest.is_valid(),
)
# Create an Election Builder
self.election_builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS,
self.QUORUM, self.manifest)
self._assert_message(
ElectionBuilder.__qualname__,
f"Created with number_of_guardians: {self.NUMBER_OF_GUARDIANS} quorum: {self.QUORUM}",
)
# Move on to the Key Ceremony
def step_1_key_ceremony(self) -> None:
"""
Using the NUMBER_OF_GUARDIANS, generate public-private keypairs and share
representations of those keys with QUORUM of other Guardians. Then, combine
the public election keys to make a joint election key that is used to encrypt ballots
"""
# Setup Guardians
for i in range(self.NUMBER_OF_GUARDIANS):
self.guardians.append(
Guardian(
"guardian_" + str(i + 1),
i + 1,
self.NUMBER_OF_GUARDIANS,
self.QUORUM,
))
# Setup Mediator
self.mediator = KeyCeremonyMediator("mediator_1",
self.guardians[0].ceremony_details)
# ROUND 1: Public Key Sharing
# Announce
for guardian in self.guardians:
self.mediator.announce(guardian.share_public_keys())
# Share Keys
for guardian in self.guardians:
announced_keys = self.mediator.share_announced()
for key_set in announced_keys:
if guardian.id is not key_set.election.owner_id:
guardian.save_guardian_public_keys(key_set)
self._assert_message(
KeyCeremonyMediator.all_guardians_announced.__qualname__,
"Confirms all guardians have shared their public keys",
self.mediator.all_guardians_announced(),
)
# ROUND 2: Election Partial Key Backup Sharing
# Share Backups
for sending_guardian in self.guardians:
sending_guardian.generate_election_partial_key_backups(
identity_auxiliary_encrypt)
backups = []
for designated_guardian in self.guardians:
if designated_guardian.id != sending_guardian.id:
backups.append(
sending_guardian.share_election_partial_key_backup(
designated_guardian.id))
self.mediator.receive_backups(backups)
self._assert_message(
KeyCeremonyMediator.receive_backups.__qualname__,
"Receive election partial key backups from key owning guardian",
len(backups) == NUMBER_OF_GUARDIANS - 1,
)
self._assert_message(
KeyCeremonyMediator.all_backups_available.__qualname__,
"Confirm all guardians have shared their election partial key backups",
self.mediator.all_backups_available(),
)
# Receive Backups
for designated_guardian in self.guardians:
backups = self.mediator.share_backups(designated_guardian.id)
self._assert_message(
KeyCeremonyMediator.share_backups.__qualname__,
"Share election partial key backups for the designated guardian",
len(backups) == NUMBER_OF_GUARDIANS - 1,
)
for backup in backups:
designated_guardian.save_election_partial_key_backup(backup)
# ROUND 3: Verification of Backups
# Verify Backups
for designated_guardian in self.guardians:
verifications = []
for backup_owner in self.guardians:
if designated_guardian.id is not backup_owner.id:
verification = (
designated_guardian.verify_election_partial_key_backup(
backup_owner.id, identity_auxiliary_encrypt))
verifications.append(verification)
self.mediator.receive_backup_verifications(verifications)
self._assert_message(
KeyCeremonyMediator.all_backups_verified.__qualname__,
"Confirms all guardians have verified the backups of all other guardians",
self.mediator.all_backups_verified(),
)
# FINAL: Publish Joint Key
joint_key = self.mediator.publish_joint_key()
self._assert_message(
KeyCeremonyMediator.publish_joint_key.__qualname__,
"Publishes the Joint Election Key",
joint_key is not None,
)
# Build the Election
self.election_builder.set_public_key(
get_optional(joint_key).joint_public_key)
self.election_builder.set_commitment_hash(
get_optional(joint_key).commitment_hash)
self.internal_manifest, self.context = get_optional(
self.election_builder.build())
self.constants = ElectionConstants()
# Move on to encrypting ballots
def step_2_encrypt_votes(self) -> None:
"""
Using the `CiphertextElectionContext` encrypt ballots for the election
"""
# Configure the Encryption Device
self.device = ElectionFactory.get_encryption_device()
self.encrypter = EncryptionMediator(self.internal_manifest,
self.context, self.device)
self._assert_message(
EncryptionDevice.__qualname__,
f"Ready to encrypt at location: {self.device.location}",
)
# Load some Ballots
self.plaintext_ballots = BallotFactory().get_simple_ballots_from_file()
self._assert_message(
PlaintextBallot.__qualname__,
f"Loaded ballots: {len(self.plaintext_ballots)}",
len(self.plaintext_ballots) > 0,
)
# Encrypt the Ballots
for plaintext_ballot in self.plaintext_ballots:
encrypted_ballot = self.encrypter.encrypt(plaintext_ballot)
self._assert_message(
EncryptionMediator.encrypt.__qualname__,
f"Ballot Id: {plaintext_ballot.object_id}",
encrypted_ballot is not None,
)
self.ciphertext_ballots.append(get_optional(encrypted_ballot))
# Next, we cast or spoil the ballots
def step_3_cast_and_spoil(self) -> None:
"""
Accept each ballot by marking it as either cast or spoiled.
This example demonstrates one way to accept ballots using the `BallotBox` class
"""
# Configure the Ballot Box
self.ballot_store = DataStore()
self.ballot_box = BallotBox(self.internal_manifest, self.context,
self.ballot_store)
# Randomly cast or spoil the ballots
for ballot in self.ciphertext_ballots:
if randint(0, 1):
submitted_ballot = self.ballot_box.cast(ballot)
else:
submitted_ballot = self.ballot_box.spoil(ballot)
self._assert_message(
BallotBox.__qualname__,
f"Submitted Ballot Id: {ballot.object_id} state: {get_optional(submitted_ballot).state}",
submitted_ballot is not None,
)
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 compare_results(self) -> None:
"""
Compare the results to ensure the decryption was done correctly
"""
print(f"""
{'-'*40}
# Election Results:
""")
# Create a representation of each contest's tally
selection_ids = [
selection.object_id for contest in self.manifest.contests
for selection in contest.ballot_selections
]
expected_plaintext_tally: Dict[str, int] = {
key: 0
for key in selection_ids
}
# Tally the expected values from the loaded ballots
for ballot in self.plaintext_ballots:
if (get_optional(self.ballot_store.get(
ballot.object_id)).state == BallotBoxState.CAST):
for contest in ballot.contests:
for selection in contest.ballot_selections:
expected_plaintext_tally[
selection.object_id] += selection.vote
# Compare the expected tally to the decrypted tally
for tally_contest in self.plaintext_tally.contests.values():
print(f" Contest: {tally_contest.object_id}")
for tally_selection in tally_contest.selections.values():
expected = expected_plaintext_tally[tally_selection.object_id]
self._assert_message(
f" - Selection: {tally_selection.object_id}",
f"expected: {expected}, actual: {tally_selection.tally}",
expected == tally_selection.tally,
)
print(f"\n{'-'*40}\n")
# Compare the expected values for each spoiled ballot
for ballot in self.plaintext_ballots:
if (get_optional(self.ballot_store.get(
ballot.object_id)).state == BallotBoxState.SPOILED):
print(f"\nSpoiled Ballot: {ballot.object_id}")
for contest in ballot.contests:
print(f"\n Contest: {contest.object_id}")
for selection in contest.ballot_selections:
expected = selection.vote
decrypted_selection = (self.plaintext_spoiled_ballots[
ballot.object_id].contests[contest.object_id].
selections[selection.object_id])
self._assert_message(
f" - Selection: {selection.object_id}",
f"expected: {expected}, actual: {decrypted_selection.tally}",
expected == decrypted_selection.tally,
)
def step_5_publish_and_verify(self) -> None:
"""Publish and verify steps of the election"""
self.publish_results()
self.verify_results()
if self.REMOVE_OUTPUT:
rmtree(RESULTS_DIR)
def publish_results(self) -> None:
"""
Publish results/artifacts of the election
"""
self.guardian_records = [
guardian.publish() for guardian in self.guardians
]
publish(
self.manifest,
self.context,
self.constants,
[self.device],
self.ballot_store.all(),
self.plaintext_spoiled_ballots.values(),
self.ciphertext_tally.publish(),
self.plaintext_tally,
self.guardian_records,
RESULTS_DIR,
)
self._assert_message(
"Publish",
f"Artifacts published to: {RESULTS_DIR}",
path.exists(RESULTS_DIR),
)
def verify_results(self) -> None:
"""Verify results of election"""
# Deserialize
manifest_from_file = Manifest.from_json_file(MANIFEST_FILE_NAME,
RESULTS_DIR)
self.assertEqual(self.manifest, manifest_from_file)
context_from_file = CiphertextElectionContext.from_json_file(
CONTEXT_FILE_NAME, RESULTS_DIR)
self.assertEqual(self.context, context_from_file)
constants_from_file = ElectionConstants.from_json_file(
CONSTANTS_FILE_NAME, RESULTS_DIR)
self.assertEqual(self.constants, constants_from_file)
device_name = DEVICE_PREFIX + str(self.device.uuid)
device_from_file = EncryptionDevice.from_json_file(
device_name, DEVICES_DIR)
self.assertEqual(self.device, device_from_file)
for ballot in self.ballot_store.all():
name = BALLOT_PREFIX + ballot.object_id
ballot_from_file = SubmittedBallot.from_json_file(
name, BALLOTS_DIR)
self.assertEqual(ballot, ballot_from_file)
for spoiled_ballot in self.plaintext_spoiled_ballots.values():
name = BALLOT_PREFIX + spoiled_ballot.object_id
spoiled_ballot_from_file = PlaintextTally.from_json_file(
name, SPOILED_DIR)
self.assertEqual(spoiled_ballot, spoiled_ballot_from_file)
published_ciphertext_tally_from_file = PublishedCiphertextTally.from_json_file(
ENCRYPTED_TALLY_FILE_NAME, RESULTS_DIR)
self.assertEqual(self.ciphertext_tally.publish(),
published_ciphertext_tally_from_file)
plainttext_tally_from_file = PlaintextTally.from_json_file(
TALLY_FILE_NAME, RESULTS_DIR)
self.assertEqual(self.plaintext_tally, plainttext_tally_from_file)
for guardian_record in self.guardian_records:
set_name = COEFFICIENT_PREFIX + guardian_record.guardian_id
guardian_record_from_file = GuardianRecord.from_json_file(
set_name, GUARDIAN_DIR)
self.assertEqual(guardian_record, guardian_record_from_file)
def _assert_message(self,
name: str,
message: str,
condition: Union[Callable, bool] = True) -> None:
if callable(condition):
result = condition()
else:
result = condition
print(f"{name}: {message}: {result}")
self.assertTrue(result)
class ElectionSampleDataGenerator:
"""
Generates sample data for an example election using the "Hamilton County" data set.
"""
election_factory: ElectionFactory
ballot_factory: BallotFactory
encryption_device: EncryptionDevice
encrypter: EncryptionMediator
def __init__(self) -> None:
"""Initialize the class"""
self.election_factory = ElectionFactory()
self.ballot_factory = BallotFactory()
self.encryption_device = EncryptionDevice(f"polling-place-{str(uuid.uuid1())}")
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
(
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) < spoil_rate:
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 use_all_guardians or i < QUORUM:
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
)
class ElectionSampleDataGenerator:
"""
Generates sample data for an example election using the "Hamilton County" data set.
"""
election_factory: ElectionFactory
ballot_factory: BallotFactory
encryption_device: EncryptionDevice
encrypter: EncryptionMediator
def __init__(self) -> None:
"""Initialize the class"""
self.election_factory = ElectionFactory()
self.ballot_factory = BallotFactory()
self.encryption_device = EncryptionDevice(f"polling-place-{uuid.uuid1}")
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
)
class TestDecryptionMediator(TestCase):
NUMBER_OF_GUARDIANS = 3
QUORUM = 2
CEREMONY_DETAILS = CeremonyDetails(NUMBER_OF_GUARDIANS, QUORUM)
def setUp(self):
self.key_ceremony = KeyCeremonyMediator(self.CEREMONY_DETAILS)
self.guardians: List[Guardian] = []
# Setup Guardians
for i in range(self.NUMBER_OF_GUARDIANS):
sequence = i + 2
self.guardians.append(
Guardian(
"guardian_" + str(sequence),
sequence,
self.NUMBER_OF_GUARDIANS,
self.QUORUM,
))
# Attendance (Public Key Share)
for guardian in self.guardians:
self.key_ceremony.announce(guardian)
self.key_ceremony.orchestrate(identity_auxiliary_encrypt)
self.key_ceremony.verify(identity_auxiliary_decrypt)
self.joint_public_key = self.key_ceremony.publish_joint_key()
self.assertIsNotNone(self.joint_public_key)
# setup the election
self.election = election_factory.get_fake_election()
builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS, self.QUORUM,
self.election)
self.assertIsNone(
builder.build()) # Can't build without the public key
builder.set_public_key(self.joint_public_key)
self.metadata, self.context = get_optional(builder.build())
self.encryption_device = EncryptionDevice("location")
self.ballot_marking_device = EncryptionMediator(
self.metadata, self.context, self.encryption_device)
# get some fake ballots
self.fake_cast_ballot = ballot_factory.get_fake_ballot(
self.metadata, "some-unique-ballot-id-cast")
self.more_fake_ballots = []
for i in range(10):
self.more_fake_ballots.append(
ballot_factory.get_fake_ballot(
self.metadata, f"some-unique-ballot-id-cast{i}"))
self.fake_spoiled_ballot = ballot_factory.get_fake_ballot(
self.metadata, "some-unique-ballot-id-spoiled")
self.assertTrue(
self.fake_cast_ballot.is_valid(
self.metadata.ballot_styles[0].object_id))
self.assertTrue(
self.fake_spoiled_ballot.is_valid(
self.metadata.ballot_styles[0].object_id))
self.expected_plaintext_tally = accumulate_plaintext_ballots(
[self.fake_cast_ballot] + self.more_fake_ballots)
# Fill in the expected values with any missing selections
# that were not made on any ballots
selection_ids = set([
selection.object_id for contest in self.metadata.contests
for selection in contest.ballot_selections
])
missing_selection_ids = selection_ids.difference(
set(self.expected_plaintext_tally))
for id in missing_selection_ids:
self.expected_plaintext_tally[id] = 0
# Encrypt
encrypted_fake_cast_ballot = self.ballot_marking_device.encrypt(
self.fake_cast_ballot)
encrypted_fake_spoiled_ballot = self.ballot_marking_device.encrypt(
self.fake_spoiled_ballot)
self.assertIsNotNone(encrypted_fake_cast_ballot)
self.assertIsNotNone(encrypted_fake_spoiled_ballot)
self.assertTrue(
encrypted_fake_cast_ballot.is_valid_encryption(
self.context.crypto_extended_base_hash, self.joint_public_key))
# encrypt some more fake ballots
self.more_fake_encrypted_ballots = []
for fake_ballot in self.more_fake_ballots:
self.more_fake_encrypted_ballots.append(
self.ballot_marking_device.encrypt(fake_ballot))
# configure the ballot box
ballot_store = BallotStore()
ballot_box = BallotBox(self.metadata, self.context, ballot_store)
ballot_box.cast(encrypted_fake_cast_ballot)
ballot_box.spoil(encrypted_fake_spoiled_ballot)
# Cast some more fake ballots
for fake_ballot in self.more_fake_encrypted_ballots:
ballot_box.cast(fake_ballot)
# generate encrypted tally
self.ciphertext_tally = tally_ballots(ballot_store, self.metadata,
self.context)
def tearDown(self):
self.key_ceremony.reset(
CeremonyDetails(self.NUMBER_OF_GUARDIANS, self.QUORUM))
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_compute_selection(self):
# Arrange
first_selection = [
selection for contest in self.ciphertext_tally.cast.values()
for selection in contest.tally_selections.values()
][0]
# act
result = compute_decryption_share_for_selection(
self.guardians[0], first_selection, self.context)
# assert
self.assertIsNotNone(result)
def test_compute_compensated_selection_failure(self):
# Arrange
first_selection = [
selection for contest in self.ciphertext_tally.cast.values()
for selection in contest.tally_selections.values()
][0]
# Act
self.guardians[0]._guardian_election_partial_key_backups.pop(
self.guardians[2].object_id)
self.assertIsNone(self.guardians[0].recovery_public_key_for(
self.guardians[2].object_id))
result = compute_compensated_decryption_share_for_selection(
self.guardians[0],
self.guardians[2].object_id,
first_selection,
self.context,
identity_auxiliary_decrypt,
)
# Assert
self.assertIsNone(result)
def test_compute_compensated_selection(self):
"""
demonstrates the complete workflow for computing a comepnsated decryption share
For one selection. It is useful for verifying that the workflow is correct
"""
# Arrange
first_selection = [
selection for contest in self.ciphertext_tally.cast.values()
for selection in contest.tally_selections.values()
][0]
# Compute lagrange coefficients for the guardians that are present
lagrange_0 = compute_lagrange_coefficient(
self.guardians[0].sequence_order,
*[self.guardians[1].sequence_order],
)
lagrange_1 = compute_lagrange_coefficient(
self.guardians[1].sequence_order,
*[self.guardians[0].sequence_order],
)
print(
f"lagrange: sequence_orders: ({self.guardians[0].sequence_order}, {self.guardians[1].sequence_order}, {self.guardians[2].sequence_order})\n"
)
print(lagrange_0)
print(lagrange_1)
# compute their shares
share_0 = compute_decryption_share_for_selection(
self.guardians[0], first_selection, self.context)
share_1 = compute_decryption_share_for_selection(
self.guardians[1], first_selection, self.context)
self.assertIsNotNone(share_0)
self.assertIsNotNone(share_1)
# compute compensations shares for the missing guardian
compensation_0 = compute_compensated_decryption_share_for_selection(
self.guardians[0],
self.guardians[2].object_id,
first_selection,
self.context,
identity_auxiliary_decrypt,
)
compensation_1 = compute_compensated_decryption_share_for_selection(
self.guardians[1],
self.guardians[2].object_id,
first_selection,
self.context,
identity_auxiliary_decrypt,
)
self.assertIsNotNone(compensation_0)
self.assertIsNotNone(compensation_1)
print("\nSHARES:")
print(compensation_0)
print(compensation_1)
# Check the share proofs
self.assertTrue(
compensation_0.proof.is_valid(
first_selection.message,
get_optional(self.guardians[0].recovery_public_key_for(
self.guardians[2].object_id)),
compensation_0.share,
self.context.crypto_extended_base_hash,
))
self.assertTrue(
compensation_1.proof.is_valid(
first_selection.message,
get_optional(self.guardians[1].recovery_public_key_for(
self.guardians[2].object_id)),
compensation_1.share,
self.context.crypto_extended_base_hash,
))
share_pow_p = [
pow_p(compensation_0.share, lagrange_0),
pow_p(compensation_1.share, lagrange_1),
]
print("\nSHARE_POW_P")
print(share_pow_p)
# reconstruct the missing share from the compensation shares
reconstructed_share = mult_p(*[
pow_p(compensation_0.share, lagrange_0),
pow_p(compensation_1.share, lagrange_1),
])
print("\nRECONSTRUCTED SHARE\n")
print(reconstructed_share)
share_2 = CiphertextDecryptionSelection(
first_selection.object_id,
self.guardians[2].object_id,
first_selection.description_hash,
reconstructed_share,
{
self.guardians[0].object_id: compensation_0,
self.guardians[1].object_id: compensation_1,
},
)
# Decrypt the result
result = decrypt_selection_with_decryption_shares(
first_selection,
{
self.guardians[0].object_id: (
self.guardians[0].share_election_public_key().key,
share_0,
),
self.guardians[1].object_id: (
self.guardians[1].share_election_public_key().key,
share_1,
),
self.guardians[2].object_id: (
self.guardians[2].share_election_public_key().key,
share_2,
),
},
self.context.crypto_extended_base_hash,
)
print(result)
self.assertIsNotNone(result)
self.assertEqual(
result.plaintext,
self.expected_plaintext_tally[first_selection.object_id])
def test_decrypt_selection_all_present(self):
# Arrange
# find the first selection
first_contest = [
contest for contest in self.ciphertext_tally.cast.values()
][0]
first_selection = list(first_contest.tally_selections.values())[0]
# 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)
# build type: Dict[GUARDIAN_ID, Tuple[ELECTION_PUBLIC_KEY, TallyDecryptionShare]]
shares = {
self.guardians[0].object_id: (
self.guardians[0].share_election_public_key().key,
first_share.contests[first_contest.object_id].selections[
first_selection.object_id],
),
self.guardians[1].object_id: (
self.guardians[1].share_election_public_key().key,
second_share.contests[first_contest.object_id].selections[
first_selection.object_id],
),
self.guardians[2].object_id: (
self.guardians[2].share_election_public_key().key,
third_share.contests[first_contest.object_id].selections[
first_selection.object_id],
),
}
# act
result = decrypt_selection_with_decryption_shares(
first_selection, shares, self.context.crypto_extended_base_hash)
# assert
self.assertIsNotNone(result)
self.assertEqual(
self.expected_plaintext_tally[first_selection.object_id],
result.plaintext)
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_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)
# Verify we get the same tally back if we call again
another_decrypted_tally = subject.get_plaintext_tally()
self.assertEqual(decrypted_tallies, another_decrypted_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)
@settings(
deadline=timedelta(milliseconds=15000),
suppress_health_check=[HealthCheck.too_slow],
max_examples=8,
# disabling the "shrink" phase, because it runs very slowly
phases=[Phase.explicit, Phase.reuse, Phase.generate, Phase.target],
)
@given(data(), integers(1, 3), integers(2, 5))
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_encrypted_tally(
self,
metadata: InternalElectionDescription,
context: CiphertextElectionContext,
ballots: List[PlaintextBallot],
) -> CiphertextTally:
# encrypt each ballot
store = BallotStore()
for ballot in ballots:
encrypted_ballot = encrypt_ballot(ballot, metadata, context,
int_to_q_unchecked(1))
self.assertIsNotNone(encrypted_ballot)
# add to the ballot store
store.set(
encrypted_ballot.object_id,
from_ciphertext_ballot(encrypted_ballot, BallotBoxState.CAST),
)
tally = tally_ballots(store, metadata, context)
self.assertIsNotNone(tally)
return get_optional(tally)
def _convert_to_selections(self, tally: PlaintextTally) -> Dict[str, int]:
plaintext_selections: Dict[str, int] = {}
for _, contest in tally.contests.items():
for selection_id, selection in contest.selections.items():
plaintext_selections[selection_id] = selection.plaintext
return plaintext_selections
class TestDecryptWithShares(TestCase):
"""Test decrypt with shares methods"""
NUMBER_OF_GUARDIANS = 3
QUORUM = 2
CEREMONY_DETAILS = CeremonyDetails(NUMBER_OF_GUARDIANS, QUORUM)
def setUp(self):
# Key Ceremony
self.key_ceremony_mediator = KeyCeremonyMediator(
"key_ceremony_mediator_mediator", self.CEREMONY_DETAILS)
self.guardians: List[Guardian] = KeyCeremonyHelper.create_guardians(
self.CEREMONY_DETAILS)
KeyCeremonyHelper.perform_full_ceremony(self.guardians,
self.key_ceremony_mediator)
self.joint_public_key = self.key_ceremony_mediator.publish_joint_key()
# Setup the election
manifest = election_factory.get_fake_manifest()
builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS, self.QUORUM,
manifest)
builder.set_public_key(self.joint_public_key.joint_public_key)
builder.set_commitment_hash(self.joint_public_key.commitment_hash)
self.internal_manifest, self.context = get_optional(builder.build())
self.encryption_device = election_factory.get_encryption_device()
self.ballot_marking_device = EncryptionMediator(
self.internal_manifest, self.context, self.encryption_device)
# get some fake ballots
self.fake_cast_ballot = ballot_factory.get_fake_ballot(
self.internal_manifest, "some-unique-ballot-id-cast")
self.more_fake_ballots = []
for i in range(10):
self.more_fake_ballots.append(
ballot_factory.get_fake_ballot(
self.internal_manifest, f"some-unique-ballot-id-cast{i}"))
self.fake_spoiled_ballot = ballot_factory.get_fake_ballot(
self.internal_manifest, "some-unique-ballot-id-spoiled")
self.more_fake_spoiled_ballots = []
for i in range(2):
self.more_fake_spoiled_ballots.append(
ballot_factory.get_fake_ballot(
self.internal_manifest,
f"some-unique-ballot-id-spoiled{i}"))
self.assertTrue(
self.fake_cast_ballot.is_valid(
self.internal_manifest.ballot_styles[0].object_id))
self.assertTrue(
self.fake_spoiled_ballot.is_valid(
self.internal_manifest.ballot_styles[0].object_id))
self.expected_plaintext_tally = accumulate_plaintext_ballots(
[self.fake_cast_ballot] + self.more_fake_ballots)
# Fill in the expected values with any missing selections
# that were not made on any ballots
selection_ids = {
selection.object_id
for contest in self.internal_manifest.contests
for selection in contest.ballot_selections
}
missing_selection_ids = selection_ids.difference(
set(self.expected_plaintext_tally))
for id in missing_selection_ids:
self.expected_plaintext_tally[id] = 0
# Encrypt
self.encrypted_fake_cast_ballot = self.ballot_marking_device.encrypt(
self.fake_cast_ballot)
self.encrypted_fake_spoiled_ballot = self.ballot_marking_device.encrypt(
self.fake_spoiled_ballot)
# encrypt some more fake ballots
self.more_fake_encrypted_ballots = []
for fake_ballot in self.more_fake_ballots:
self.more_fake_encrypted_ballots.append(
self.ballot_marking_device.encrypt(fake_ballot))
# encrypt some more fake ballots
self.more_fake_encrypted_spoiled_ballots = []
for fake_ballot in self.more_fake_spoiled_ballots:
self.more_fake_encrypted_spoiled_ballots.append(
self.ballot_marking_device.encrypt(fake_ballot))
# configure the ballot box
ballot_store = DataStore()
ballot_box = BallotBox(self.internal_manifest, self.context,
ballot_store)
ballot_box.cast(self.encrypted_fake_cast_ballot)
ballot_box.spoil(self.encrypted_fake_spoiled_ballot)
# Cast some more fake ballots
for fake_ballot in self.more_fake_encrypted_ballots:
ballot_box.cast(fake_ballot)
# Spoil some more fake ballots
for fake_ballot in self.more_fake_encrypted_spoiled_ballots:
ballot_box.spoil(fake_ballot)
# generate encrypted tally
self.ciphertext_tally = tally_ballots(ballot_store,
self.internal_manifest,
self.context)
self.ciphertext_ballots = get_ballots(ballot_store,
BallotBoxState.SPOILED)
def tearDown(self):
self.key_ceremony_mediator.reset(
CeremonyDetails(self.NUMBER_OF_GUARDIANS, self.QUORUM))
def test_decrypt_selection_with_all_guardians_present(self):
# Arrange
available_guardians = self.guardians
# find the first selection
first_contest = list(self.ciphertext_tally.contests.values())[0]
first_selection = list(first_contest.selections.values())[0]
print(first_contest.object_id)
print(first_selection.object_id)
# precompute decryption shares for specific selection for the guardians
shares: Dict[GUARDIAN_ID,
Tuple[ELECTION_PUBLIC_KEY, DecryptionShare]] = {
guardian.id: (
guardian.share_election_public_key().key,
compute_decryption_share(
guardian._election_keys,
self.ciphertext_tally,
self.context,
).contests[first_contest.object_id].selections[
first_selection.object_id],
)
for guardian in available_guardians
}
# Act
result = decrypt_selection_with_decryption_shares(
first_selection, shares, self.context.crypto_extended_base_hash)
# Assert
self.assertIsNotNone(result)
self.assertEqual(
self.expected_plaintext_tally[first_selection.object_id],
result.tally)
def test_decrypt_ballot_with_all_guardians_present(self):
# Arrange
# precompute decryption shares for the guardians
available_guardians = self.guardians
plaintext_ballot = self.fake_cast_ballot
encrypted_ballot = self.encrypted_fake_cast_ballot
shares = {
available_guardian.id: compute_decryption_share_for_ballot(
available_guardian._election_keys,
encrypted_ballot,
self.context,
)
for available_guardian in available_guardians
}
# act
result = decrypt_ballot(
encrypted_ballot,
shares,
self.context.crypto_extended_base_hash,
)
# assert
self.assertIsNotNone(result)
for contest in plaintext_ballot.contests:
for selection in contest.ballot_selections:
expected_tally = selection.vote
actual_tally = (result.contests[contest.object_id].selections[
selection.object_id].tally)
self.assertEqual(expected_tally, actual_tally)
def test_decrypt_ballot_with_missing_guardians(self):
# Arrange
# precompute decryption shares for the guardians
plaintext_ballot = self.fake_cast_ballot
encrypted_ballot = self.encrypted_fake_cast_ballot
available_guardians = self.guardians[0:2]
missing_guardian = self.guardians[2]
available_shares = {
available_guardian.id: compute_decryption_share_for_ballot(
available_guardian._election_keys,
encrypted_ballot,
self.context,
)
for available_guardian in available_guardians
}
compensated_shares = {
available_guardian.id:
compute_compensated_decryption_share_for_ballot(
available_guardian.share_election_public_key(),
available_guardian._auxiliary_keys,
missing_guardian.share_election_public_key(),
get_optional(
available_guardian._guardian_election_partial_key_backups.
get(missing_guardian.id)),
encrypted_ballot,
self.context,
identity_auxiliary_decrypt,
)
for available_guardian in available_guardians
}
lagrange_coefficients = compute_lagrange_coefficients_for_guardians([
guardian.share_election_public_key()
for guardian in available_guardians
])
reconstructed_share = reconstruct_decryption_share_for_ballot(
missing_guardian.share_election_public_key(),
encrypted_ballot,
compensated_shares,
lagrange_coefficients,
)
all_shares = {
**available_shares, missing_guardian.id: reconstructed_share
}
# act
result = decrypt_ballot(
encrypted_ballot,
all_shares,
self.context.crypto_extended_base_hash,
)
# assert
self.assertIsNotNone(result)
for contest in plaintext_ballot.contests:
for selection in contest.ballot_selections:
expected_tally = selection.vote
actual_tally = (result.contests[contest.object_id].selections[
selection.object_id].tally)
self.assertEqual(expected_tally, actual_tally)
class TestDecryptionMediator(TestCase):
NUMBER_OF_GUARDIANS = 3
QUORUM = 2
CEREMONY_DETAILS = CeremonyDetails(NUMBER_OF_GUARDIANS, QUORUM)
def setUp(self):
self.key_ceremony = KeyCeremonyMediator(self.CEREMONY_DETAILS)
self.guardians: List[Guardian] = []
# Setup Guardians
for i in range(self.NUMBER_OF_GUARDIANS):
self.guardians.append(
Guardian("guardian_" + str(i), i, self.NUMBER_OF_GUARDIANS, self.QUORUM)
)
# Attendance (Public Key Share)
for guardian in self.guardians:
self.key_ceremony.announce(guardian)
self.key_ceremony.orchestrate()
self.key_ceremony.verify()
self.joint_public_key = self.key_ceremony.publish_joint_key()
self.assertIsNotNone(self.joint_public_key)
# setup the election
self.election = election_factory.get_fake_election()
builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS, self.QUORUM, self.election)
self.assertIsNone(builder.build()) # Can't build without the public key
builder.set_public_key(self.joint_public_key)
self.metadata, self.context = get_optional(builder.build())
self.encryption_device = EncryptionDevice("location")
self.ballot_marking_device = EncryptionMediator(
self.metadata, self.context, self.encryption_device
)
# get some fake ballots
self.fake_cast_ballot = ballot_factory.get_fake_ballot(
self.metadata, "some-unique-ballot-id-cast"
)
self.fake_spoiled_ballot = ballot_factory.get_fake_ballot(
self.metadata, "some-unique-ballot-id-spoiled"
)
self.assertTrue(
self.fake_cast_ballot.is_valid(self.metadata.ballot_styles[0].object_id)
)
self.assertTrue(
self.fake_spoiled_ballot.is_valid(self.metadata.ballot_styles[0].object_id)
)
self.expected_plaintext_tally = accumulate_plaintext_ballots(
[self.fake_cast_ballot]
)
# Fill in any missing selections that were not made on any ballots
selection_ids = set(
[
selection.object_id
for contest in self.metadata.contests
for selection in contest.ballot_selections
]
)
missing_selection_ids = selection_ids.difference(
set(self.expected_plaintext_tally)
)
for id in missing_selection_ids:
self.expected_plaintext_tally[id] = 0
# Encrypt
encrypted_fake_cast_ballot = self.ballot_marking_device.encrypt(
self.fake_cast_ballot
)
encrypted_fake_spoiled_ballot = self.ballot_marking_device.encrypt(
self.fake_spoiled_ballot
)
self.assertIsNotNone(encrypted_fake_cast_ballot)
self.assertIsNotNone(encrypted_fake_spoiled_ballot)
self.assertTrue(
encrypted_fake_cast_ballot.is_valid_encryption(
self.context.crypto_extended_base_hash, self.joint_public_key
)
)
# configure the ballot box
ballot_store = BallotStore()
ballot_box = BallotBox(self.metadata, self.context, ballot_store)
ballot_box.cast(encrypted_fake_cast_ballot)
ballot_box.spoil(encrypted_fake_spoiled_ballot)
# generate encrypted tally
self.ciphertext_tally = tally_ballots(ballot_store, self.metadata, self.context)
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.assertIsNone(subject.announce(self.guardians[0]))
# Cannot submit another share internally
self.assertFalse(
subject._submit_decryption_share(
DecryptionShare(self.guardians[0].object_id, {}, {})
)
)
# Cannot get plaintext tally without a quorum
self.assertIsNone(subject.get_plaintext_tally())
def test_compute_selection(self):
# Arrange
first_selection = [
selection
for contest in self.ciphertext_tally.cast.values()
for selection in contest.tally_selections.values()
][0]
# act
result = _compute_decryption_for_selection(
self.guardians[0], first_selection, self.context
)
# assert
self.assertIsNotNone(result)
def test_decrypt_selection(self):
# Arrange
# find the first selection
first_contest = [contest for contest in self.ciphertext_tally.cast.values()][0]
first_selection = list(first_contest.tally_selections.values())[0]
# 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.contests[first_contest.object_id]
.selections[first_selection.object_id]
.share,
self.guardians[1]
.object_id: second_share.contests[first_contest.object_id]
.selections[first_selection.object_id]
.share,
self.guardians[2]
.object_id: third_share.contests[first_contest.object_id]
.selections[first_selection.object_id]
.share,
}
# act
result = decrypt_selection_with_decryption_shares(first_selection, shares)
# assert
self.assertIsNotNone(result)
self.assertEqual(
self.expected_plaintext_tally[first_selection.object_id], result.plaintext
)
def test_decrypt_spoiled_ballots(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 = subject._decrypt_spoiled_ballots(
self.ciphertext_tally.spoiled_ballots, shares
)
# 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_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)
@settings(
deadline=timedelta(milliseconds=10000),
suppress_health_check=[HealthCheck.too_slow],
max_examples=1,
# disabling the "shrink" phase, because it runs very slowly
phases=[Phase.explicit, Phase.reuse, Phase.generate, Phase.target],
)
@given(data(), integers(1, 3), integers(2, 5))
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_encrypted_tally(
self,
metadata: InternalElectionDescription,
context: CiphertextElectionContext,
ballots: List[PlaintextBallot],
) -> CiphertextTally:
# encrypt each ballot
store = BallotStore()
for ballot in ballots:
encrypted_ballot = encrypt_ballot(
ballot, metadata, context, int_to_q_unchecked(1)
)
self.assertIsNotNone(encrypted_ballot)
# add to the ballot store
store.set(
encrypted_ballot.object_id,
from_ciphertext_ballot(encrypted_ballot, BallotBoxState.CAST),
)
tally = tally_ballots(store, metadata, context)
self.assertIsNotNone(tally)
return get_optional(tally)
def _convert_to_selections(self, tally: PlaintextTally) -> Dict[str, int]:
plaintext_selections: Dict[str, int] = {}
for _, contest in tally.contests.items():
for selection_id, selection in contest.selections.items():
plaintext_selections[selection_id] = selection.plaintext
return plaintext_selections
class TestDecryptionMediator(TestCase):
"""Test suite for DecryptionMediator"""
NUMBER_OF_GUARDIANS = 3
QUORUM = 2
CEREMONY_DETAILS = CeremonyDetails(NUMBER_OF_GUARDIANS, QUORUM)
internal_manifest: InternalManifest
decryption_mediator_id = "mediator-id"
def setUp(self):
# Key Ceremony
key_ceremony_mediator = KeyCeremonyMediator(
"key_ceremony_mediator_mediator", self.CEREMONY_DETAILS)
self.guardians: List[Guardian] = KeyCeremonyHelper.create_guardians(
self.CEREMONY_DETAILS)
KeyCeremonyHelper.perform_full_ceremony(self.guardians,
key_ceremony_mediator)
self.joint_public_key = key_ceremony_mediator.publish_joint_key()
self.assertIsNotNone(self.joint_public_key)
# Setup the election
manifest = election_factory.get_fake_manifest()
builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS, self.QUORUM,
manifest)
self.assertIsNone(
builder.build()) # Can't build without the public key
builder.set_public_key(self.joint_public_key.joint_public_key)
builder.set_commitment_hash(self.joint_public_key.commitment_hash)
self.internal_manifest, self.context = get_optional(builder.build())
self.encryption_device = election_factory.get_encryption_device()
self.ballot_marking_device = EncryptionMediator(
self.internal_manifest, self.context, self.encryption_device)
# get some fake ballots
self.fake_cast_ballot = ballot_factory.get_fake_ballot(
self.internal_manifest, "some-unique-ballot-id-cast")
more_fake_ballots = []
for i in range(10):
more_fake_ballots.append(
ballot_factory.get_fake_ballot(
self.internal_manifest, f"some-unique-ballot-id-cast{i}"))
self.fake_spoiled_ballot = ballot_factory.get_fake_ballot(
self.internal_manifest, "some-unique-ballot-id-spoiled")
more_fake_spoiled_ballots = []
for i in range(2):
more_fake_spoiled_ballots.append(
ballot_factory.get_fake_ballot(
self.internal_manifest,
f"some-unique-ballot-id-spoiled{i}"))
self.assertTrue(
self.fake_cast_ballot.is_valid(
self.internal_manifest.ballot_styles[0].object_id))
self.assertTrue(
self.fake_spoiled_ballot.is_valid(
self.internal_manifest.ballot_styles[0].object_id))
self.expected_plaintext_tally = accumulate_plaintext_ballots(
[self.fake_cast_ballot] + more_fake_ballots)
# Fill in the expected values with any missing selections
# that were not made on any ballots
selection_ids = {
selection.object_id
for contest in self.internal_manifest.contests
for selection in contest.ballot_selections
}
missing_selection_ids = selection_ids.difference(
set(self.expected_plaintext_tally))
for id in missing_selection_ids:
self.expected_plaintext_tally[id] = 0
# Encrypt
self.encrypted_fake_cast_ballot = self.ballot_marking_device.encrypt(
self.fake_cast_ballot)
self.encrypted_fake_spoiled_ballot = self.ballot_marking_device.encrypt(
self.fake_spoiled_ballot)
self.assertIsNotNone(self.encrypted_fake_cast_ballot)
self.assertIsNotNone(self.encrypted_fake_spoiled_ballot)
self.assertTrue(
self.encrypted_fake_cast_ballot.is_valid_encryption(
self.internal_manifest.manifest_hash,
self.joint_public_key.joint_public_key,
self.context.crypto_extended_base_hash,
))
# encrypt some more fake ballots
more_fake_encrypted_ballots = []
for fake_ballot in more_fake_ballots:
more_fake_encrypted_ballots.append(
self.ballot_marking_device.encrypt(fake_ballot))
# encrypt some more fake ballots
self.more_fake_encrypted_spoiled_ballots = []
for fake_ballot in more_fake_spoiled_ballots:
self.more_fake_encrypted_spoiled_ballots.append(
self.ballot_marking_device.encrypt(fake_ballot))
# configure the ballot box
ballot_store = DataStore()
ballot_box = BallotBox(self.internal_manifest, self.context,
ballot_store)
ballot_box.cast(self.encrypted_fake_cast_ballot)
ballot_box.spoil(self.encrypted_fake_spoiled_ballot)
# Cast some more fake ballots
for fake_ballot in more_fake_encrypted_ballots:
ballot_box.cast(fake_ballot)
# Spoil some more fake ballots
for fake_ballot in self.more_fake_encrypted_spoiled_ballots:
ballot_box.spoil(fake_ballot)
# generate encrypted tally
self.ciphertext_tally = tally_ballots(ballot_store,
self.internal_manifest,
self.context)
self.ciphertext_ballots = list(
get_ballots(ballot_store, BallotBoxState.SPOILED).values())
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_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_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)
@settings(
deadline=timedelta(milliseconds=15000),
suppress_health_check=[HealthCheck.too_slow],
max_examples=8,
# disabling the "shrink" phase, because it runs very slowly
phases=[Phase.explicit, Phase.reuse, Phase.generate, Phase.target],
)
@given(data(), integers(1, 3), integers(2, 5))
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 _generate_encrypted_tally(
self,
internal_manifest: InternalManifest,
context: CiphertextElectionContext,
ballots: List[PlaintextBallot],
) -> CiphertextTally:
# encrypt each ballot
store = DataStore()
for ballot in ballots:
encrypted_ballot = encrypt_ballot(ballot, internal_manifest,
context, int_to_q_unchecked(1))
self.assertIsNotNone(encrypted_ballot)
# add to the ballot store
store.set(
encrypted_ballot.object_id,
from_ciphertext_ballot(encrypted_ballot, BallotBoxState.CAST),
)
tally = tally_ballots(store, internal_manifest, context)
self.assertIsNotNone(tally)
return get_optional(tally)
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 setUp(self):
# Key Ceremony
self.key_ceremony_mediator = KeyCeremonyMediator(
"key_ceremony_mediator_mediator", self.CEREMONY_DETAILS)
self.guardians: List[Guardian] = KeyCeremonyHelper.create_guardians(
self.CEREMONY_DETAILS)
KeyCeremonyHelper.perform_full_ceremony(self.guardians,
self.key_ceremony_mediator)
self.joint_public_key = self.key_ceremony_mediator.publish_joint_key()
# Setup the election
manifest = election_factory.get_fake_manifest()
builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS, self.QUORUM,
manifest)
builder.set_public_key(self.joint_public_key.joint_public_key)
builder.set_commitment_hash(self.joint_public_key.commitment_hash)
self.internal_manifest, self.context = get_optional(builder.build())
self.encryption_device = election_factory.get_encryption_device()
self.ballot_marking_device = EncryptionMediator(
self.internal_manifest, self.context, self.encryption_device)
# get some fake ballots
self.fake_cast_ballot = ballot_factory.get_fake_ballot(
self.internal_manifest, "some-unique-ballot-id-cast")
self.more_fake_ballots = []
for i in range(10):
self.more_fake_ballots.append(
ballot_factory.get_fake_ballot(
self.internal_manifest, f"some-unique-ballot-id-cast{i}"))
self.fake_spoiled_ballot = ballot_factory.get_fake_ballot(
self.internal_manifest, "some-unique-ballot-id-spoiled")
self.more_fake_spoiled_ballots = []
for i in range(2):
self.more_fake_spoiled_ballots.append(
ballot_factory.get_fake_ballot(
self.internal_manifest,
f"some-unique-ballot-id-spoiled{i}"))
self.assertTrue(
self.fake_cast_ballot.is_valid(
self.internal_manifest.ballot_styles[0].object_id))
self.assertTrue(
self.fake_spoiled_ballot.is_valid(
self.internal_manifest.ballot_styles[0].object_id))
self.expected_plaintext_tally = accumulate_plaintext_ballots(
[self.fake_cast_ballot] + self.more_fake_ballots)
# Fill in the expected values with any missing selections
# that were not made on any ballots
selection_ids = {
selection.object_id
for contest in self.internal_manifest.contests
for selection in contest.ballot_selections
}
missing_selection_ids = selection_ids.difference(
set(self.expected_plaintext_tally))
for id in missing_selection_ids:
self.expected_plaintext_tally[id] = 0
# Encrypt
self.encrypted_fake_cast_ballot = self.ballot_marking_device.encrypt(
self.fake_cast_ballot)
self.encrypted_fake_spoiled_ballot = self.ballot_marking_device.encrypt(
self.fake_spoiled_ballot)
# encrypt some more fake ballots
self.more_fake_encrypted_ballots = []
for fake_ballot in self.more_fake_ballots:
self.more_fake_encrypted_ballots.append(
self.ballot_marking_device.encrypt(fake_ballot))
# encrypt some more fake ballots
self.more_fake_encrypted_spoiled_ballots = []
for fake_ballot in self.more_fake_spoiled_ballots:
self.more_fake_encrypted_spoiled_ballots.append(
self.ballot_marking_device.encrypt(fake_ballot))
# configure the ballot box
ballot_store = DataStore()
ballot_box = BallotBox(self.internal_manifest, self.context,
ballot_store)
ballot_box.cast(self.encrypted_fake_cast_ballot)
ballot_box.spoil(self.encrypted_fake_spoiled_ballot)
# Cast some more fake ballots
for fake_ballot in self.more_fake_encrypted_ballots:
ballot_box.cast(fake_ballot)
# Spoil some more fake ballots
for fake_ballot in self.more_fake_encrypted_spoiled_ballots:
ballot_box.spoil(fake_ballot)
# generate encrypted tally
self.ciphertext_tally = tally_ballots(ballot_store,
self.internal_manifest,
self.context)
self.ciphertext_ballots = get_ballots(ballot_store,
BallotBoxState.SPOILED)
class TestDecryption(TestCase):
"""Test decryption methods"""
NUMBER_OF_GUARDIANS = 3
QUORUM = 2
CEREMONY_DETAILS = CeremonyDetails(NUMBER_OF_GUARDIANS, QUORUM)
def setUp(self):
# Key Ceremony
self.key_ceremony_mediator = KeyCeremonyMediator(
"key_ceremony_mediator_mediator", self.CEREMONY_DETAILS)
self.guardians: List[Guardian] = KeyCeremonyHelper.create_guardians(
self.CEREMONY_DETAILS)
KeyCeremonyHelper.perform_full_ceremony(self.guardians,
self.key_ceremony_mediator)
self.joint_public_key = self.key_ceremony_mediator.publish_joint_key()
# Setup the election
manifest = election_factory.get_fake_manifest()
builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS, self.QUORUM,
manifest)
builder.set_public_key(self.joint_public_key.joint_public_key)
builder.set_commitment_hash(self.joint_public_key.commitment_hash)
self.internal_manifest, self.context = get_optional(builder.build())
self.encryption_device = election_factory.get_encryption_device()
self.ballot_marking_device = EncryptionMediator(
self.internal_manifest, self.context, self.encryption_device)
# get some fake ballots
self.fake_cast_ballot = ballot_factory.get_fake_ballot(
self.internal_manifest, "some-unique-ballot-id-cast")
self.more_fake_ballots = []
for i in range(10):
self.more_fake_ballots.append(
ballot_factory.get_fake_ballot(
self.internal_manifest, f"some-unique-ballot-id-cast{i}"))
self.fake_spoiled_ballot = ballot_factory.get_fake_ballot(
self.internal_manifest, "some-unique-ballot-id-spoiled")
self.more_fake_spoiled_ballots = []
for i in range(2):
self.more_fake_spoiled_ballots.append(
ballot_factory.get_fake_ballot(
self.internal_manifest,
f"some-unique-ballot-id-spoiled{i}"))
self.assertTrue(
self.fake_cast_ballot.is_valid(
self.internal_manifest.ballot_styles[0].object_id))
self.assertTrue(
self.fake_spoiled_ballot.is_valid(
self.internal_manifest.ballot_styles[0].object_id))
self.expected_plaintext_tally = accumulate_plaintext_ballots(
[self.fake_cast_ballot] + self.more_fake_ballots)
# Fill in the expected values with any missing selections
# that were not made on any ballots
selection_ids = {
selection.object_id
for contest in self.internal_manifest.contests
for selection in contest.ballot_selections
}
missing_selection_ids = selection_ids.difference(
set(self.expected_plaintext_tally))
for id in missing_selection_ids:
self.expected_plaintext_tally[id] = 0
# Encrypt
self.encrypted_fake_cast_ballot = self.ballot_marking_device.encrypt(
self.fake_cast_ballot)
self.encrypted_fake_spoiled_ballot = self.ballot_marking_device.encrypt(
self.fake_spoiled_ballot)
# encrypt some more fake ballots
self.more_fake_encrypted_ballots = []
for fake_ballot in self.more_fake_ballots:
self.more_fake_encrypted_ballots.append(
self.ballot_marking_device.encrypt(fake_ballot))
# encrypt some more fake ballots
self.more_fake_encrypted_spoiled_ballots = []
for fake_ballot in self.more_fake_spoiled_ballots:
self.more_fake_encrypted_spoiled_ballots.append(
self.ballot_marking_device.encrypt(fake_ballot))
# configure the ballot box
ballot_store = DataStore()
ballot_box = BallotBox(self.internal_manifest, self.context,
ballot_store)
ballot_box.cast(self.encrypted_fake_cast_ballot)
ballot_box.spoil(self.encrypted_fake_spoiled_ballot)
# Cast some more fake ballots
for fake_ballot in self.more_fake_encrypted_ballots:
ballot_box.cast(fake_ballot)
# Spoil some more fake ballots
for fake_ballot in self.more_fake_encrypted_spoiled_ballots:
ballot_box.spoil(fake_ballot)
# generate encrypted tally
self.ciphertext_tally = tally_ballots(ballot_store,
self.internal_manifest,
self.context)
self.ciphertext_ballots: Dict[BALLOT_ID,
SubmittedBallot] = get_ballots(
ballot_store, BallotBoxState.SPOILED)
def tearDown(self):
self.key_ceremony_mediator.reset(
CeremonyDetails(self.NUMBER_OF_GUARDIANS, self.QUORUM))
# SHARE
def test_compute_decryption_share(self):
# Arrange
guardian = self.guardians[0]
# Act
# Guardian doesn't give keys
broken_secret_key = ZERO_MOD_Q
broken_guardian_key_pair = ElectionKeyPair(
guardian.id,
guardian.sequence_order,
ElGamalKeyPair(broken_secret_key,
guardian._election_keys.key_pair.public_key),
guardian._election_keys.polynomial,
)
broken_share = compute_decryption_share(
broken_guardian_key_pair,
self.ciphertext_tally,
self.context,
)
# Assert
self.assertIsNone(broken_share)
# Act
# Normal use case
share = compute_decryption_share(
guardian._election_keys,
self.ciphertext_tally,
self.context,
)
# Assert
self.assertIsNotNone(share)
def test_compute_compensated_decryption_share(self):
# Arrange
guardian = self.guardians[0]
missing_guardian = self.guardians[2]
public_key = guardian.share_election_public_key()
auxiliary_keys = guardian._auxiliary_keys
missing_guardian_public_key = missing_guardian.share_election_public_key(
)
missing_guardian_backup = missing_guardian._backups_to_share.get(
guardian.id)
# Act
share = compute_compensated_decryption_share(
public_key,
auxiliary_keys,
missing_guardian_public_key,
missing_guardian_backup,
self.ciphertext_tally,
self.context,
identity_auxiliary_decrypt,
)
# Assert
self.assertIsNotNone(share)
# SELECTION
def test_compute_selection(self):
# Arrange
first_selection = [
selection for contest in self.ciphertext_tally.contests.values()
for selection in contest.selections.values()
][0]
# act
result = compute_decryption_share_for_selection(
self.guardians[0]._election_keys, first_selection, self.context)
# assert
self.assertIsNotNone(result)
def test_compute_compensated_selection(self):
"""
demonstrates the complete workflow for computing a comepnsated decryption share
For one selection. It is useful for verifying that the workflow is correct
"""
# Arrange
available_guardian_1 = self.guardians[0]
available_guardian_2 = self.guardians[1]
missing_guardian = self.guardians[2]
available_guardian_1_key = available_guardian_1.share_election_public_key(
)
available_guardian_2_key = available_guardian_2.share_election_public_key(
)
missing_guardian_key = missing_guardian.share_election_public_key()
first_selection = [
selection for contest in self.ciphertext_tally.contests.values()
for selection in contest.selections.values()
][0]
# Compute lagrange coefficients for the guardians that are present
lagrange_0 = compute_lagrange_coefficient(
available_guardian_1.sequence_order,
*[available_guardian_2.sequence_order],
)
lagrange_1 = compute_lagrange_coefficient(
available_guardian_2.sequence_order,
*[available_guardian_1.sequence_order],
)
print((
f"lagrange: sequence_orders: ({available_guardian_1.sequence_order}, "
f"{available_guardian_2.sequence_order}, {missing_guardian.sequence_order})\n"
))
print(lagrange_0)
print(lagrange_1)
# compute their shares
share_0 = compute_decryption_share_for_selection(
available_guardian_1._election_keys, first_selection, self.context)
share_1 = compute_decryption_share_for_selection(
available_guardian_2._election_keys, first_selection, self.context)
self.assertIsNotNone(share_0)
self.assertIsNotNone(share_1)
# compute compensations shares for the missing guardian
compensation_0 = compute_compensated_decryption_share_for_selection(
available_guardian_1.share_election_public_key(),
available_guardian_1._auxiliary_keys,
missing_guardian.share_election_public_key(),
missing_guardian.share_election_partial_key_backup(
available_guardian_1.id),
first_selection,
self.context,
identity_auxiliary_decrypt,
)
compensation_1 = compute_compensated_decryption_share_for_selection(
available_guardian_2.share_election_public_key(),
available_guardian_2._auxiliary_keys,
missing_guardian.share_election_public_key(),
missing_guardian.share_election_partial_key_backup(
available_guardian_2.id),
first_selection,
self.context,
identity_auxiliary_decrypt,
)
self.assertIsNotNone(compensation_0)
self.assertIsNotNone(compensation_1)
print("\nSHARES:")
print(compensation_0)
print(compensation_1)
# Check the share proofs
self.assertTrue(
compensation_0.proof.is_valid(
first_selection.ciphertext,
compute_recovery_public_key(available_guardian_1_key,
missing_guardian_key),
compensation_0.share,
self.context.crypto_extended_base_hash,
))
self.assertTrue(
compensation_1.proof.is_valid(
first_selection.ciphertext,
compute_recovery_public_key(available_guardian_2_key,
missing_guardian_key),
compensation_1.share,
self.context.crypto_extended_base_hash,
))
share_pow_p = [
pow_p(compensation_0.share, lagrange_0),
pow_p(compensation_1.share, lagrange_1),
]
print("\nSHARE_POW_P")
print(share_pow_p)
# reconstruct the missing share from the compensation shares
reconstructed_share = mult_p(*[
pow_p(compensation_0.share, lagrange_0),
pow_p(compensation_1.share, lagrange_1),
])
print("\nRECONSTRUCTED SHARE\n")
print(reconstructed_share)
share_2 = create_ciphertext_decryption_selection(
first_selection.object_id,
missing_guardian.id,
reconstructed_share,
{
available_guardian_1.id: compensation_0,
available_guardian_2.id: compensation_1,
},
)
# Decrypt the result
result = decrypt_selection_with_decryption_shares(
first_selection,
{
available_guardian_1.id: (
available_guardian_1.share_election_public_key().key,
share_0,
),
available_guardian_2.id: (
available_guardian_2.share_election_public_key().key,
share_1,
),
missing_guardian.id: (
missing_guardian.share_election_public_key().key,
share_2,
),
},
self.context.crypto_extended_base_hash,
)
print(result)
self.assertIsNotNone(result)
self.assertEqual(
result.tally,
self.expected_plaintext_tally[first_selection.object_id])
def test_compute_compensated_selection_failure(self):
# Arrange
available_guardian = self.guardians[0]
missing_guardian = self.guardians[2]
first_selection = [
selection for contest in self.ciphertext_tally.contests.values()
for selection in contest.selections.values()
][0]
# Act
# Get backup for missing guardian instead of one sent by guardian
incorrect_backup = available_guardian.share_election_partial_key_backup(
missing_guardian.id)
result = compute_compensated_decryption_share_for_selection(
available_guardian.share_election_public_key(),
available_guardian._auxiliary_keys,
missing_guardian.share_election_public_key(),
incorrect_backup,
first_selection,
self.context,
identity_auxiliary_decrypt,
)
# Assert
self.assertIsNone(result)
def test_reconstruct_decryption_share(self):
# Arrange
available_guardians = self.guardians[0:2]
available_guardians_keys = [
guardian.share_election_public_key()
for guardian in available_guardians
]
missing_guardian = self.guardians[2]
missing_guardian_key = missing_guardian.share_election_public_key()
missing_guardian_backups = {
backup.designated_id: backup
for backup in
missing_guardian.share_election_partial_key_backups()
}
tally = self.ciphertext_tally
# Act
compensated_shares: Dict[GUARDIAN_ID, CompensatedDecryptionShare] = {
available_guardian.id: compute_compensated_decryption_share(
available_guardian.share_election_public_key(),
available_guardian._auxiliary_keys,
missing_guardian_key,
missing_guardian_backups[available_guardian.id],
tally,
self.context,
identity_auxiliary_decrypt,
)
for available_guardian in available_guardians
}
lagrange_coefficients = compute_lagrange_coefficients_for_guardians(
available_guardians_keys)
share = reconstruct_decryption_share(missing_guardian_key, tally,
compensated_shares,
lagrange_coefficients)
# Assert
self.assertEqual(self.QUORUM, len(compensated_shares))
self.assertEqual(self.QUORUM, len(lagrange_coefficients))
self.assertIsNotNone(share)
def test_reconstruct_decryption_shares_for_ballot(self):
# Arrange
available_guardians = self.guardians[0:2]
available_guardians_keys = [
guardian.share_election_public_key()
for guardian in available_guardians
]
missing_guardian = self.guardians[2]
missing_guardian_key = missing_guardian.share_election_public_key()
missing_guardian_backups = {
backup.designated_id: backup
for backup in
missing_guardian.share_election_partial_key_backups()
}
ballot = list(self.ciphertext_ballots.values())[0]
# Act
compensated_ballot_shares: Dict[GUARDIAN_ID,
CompensatedDecryptionShare] = {}
for available_guardian in available_guardians:
compensated_share = compute_compensated_decryption_share_for_ballot(
available_guardian.share_election_public_key(),
available_guardian._auxiliary_keys,
missing_guardian_key,
missing_guardian_backups[available_guardian.id],
ballot,
self.context,
identity_auxiliary_decrypt,
)
if compensated_share:
compensated_ballot_shares[
available_guardian.id] = compensated_share
lagrange_coefficients = compute_lagrange_coefficients_for_guardians(
available_guardians_keys)
missing_ballot_share = reconstruct_decryption_share_for_ballot(
missing_guardian_key,
ballot,
compensated_ballot_shares,
lagrange_coefficients,
)
# Assert
self.assertEqual(self.QUORUM, len(lagrange_coefficients))
self.assertEqual(len(available_guardians),
len(compensated_ballot_shares))
self.assertEqual(len(available_guardians), len(lagrange_coefficients))
self.assertIsNotNone(missing_ballot_share)
def test_reconstruct_decryption_share_for_ballot(self):
# Arrange
available_guardians = self.guardians[0:2]
available_guardians_keys = [
guardian.share_election_public_key()
for guardian in available_guardians
]
missing_guardian = self.guardians[2]
missing_guardian_key = missing_guardian.share_election_public_key()
missing_guardian_backups = {
backup.designated_id: backup
for backup in
missing_guardian.share_election_partial_key_backups()
}
ballot = self.ciphertext_ballots[self.fake_spoiled_ballot.object_id]
# Act
compensated_shares: Dict[GUARDIAN_ID, CompensatedDecryptionShare] = {
available_guardian.id: get_optional(
compute_compensated_decryption_share_for_ballot(
available_guardian.share_election_public_key(),
available_guardian._auxiliary_keys,
missing_guardian_key,
missing_guardian_backups[available_guardian.id],
ballot,
self.context,
identity_auxiliary_decrypt,
))
for available_guardian in available_guardians
}
lagrange_coefficients = compute_lagrange_coefficients_for_guardians(
available_guardians_keys)
share = reconstruct_decryption_share_for_ballot(
missing_guardian_key, ballot, compensated_shares,
lagrange_coefficients)
# Assert
self.assertEqual(self.QUORUM, len(compensated_shares))
self.assertEqual(self.QUORUM, len(lagrange_coefficients))
self.assertIsNotNone(share)
def setUp(self):
self.key_ceremony = KeyCeremonyMediator(self.CEREMONY_DETAILS)
self.guardians: List[Guardian] = []
# Setup Guardians
for i in range(self.NUMBER_OF_GUARDIANS):
sequence = i + 2
self.guardians.append(
Guardian(
"guardian_" + str(sequence),
sequence,
self.NUMBER_OF_GUARDIANS,
self.QUORUM,
))
# Attendance (Public Key Share)
for guardian in self.guardians:
self.key_ceremony.announce(guardian)
self.key_ceremony.orchestrate(identity_auxiliary_encrypt)
self.key_ceremony.verify(identity_auxiliary_decrypt)
self.joint_public_key = self.key_ceremony.publish_joint_key()
self.assertIsNotNone(self.joint_public_key)
# setup the election
self.election = election_factory.get_fake_election()
builder = ElectionBuilder(self.NUMBER_OF_GUARDIANS, self.QUORUM,
self.election)
self.assertIsNone(
builder.build()) # Can't build without the public key
builder.set_public_key(self.joint_public_key)
self.metadata, self.context = get_optional(builder.build())
self.encryption_device = EncryptionDevice("location")
self.ballot_marking_device = EncryptionMediator(
self.metadata, self.context, self.encryption_device)
# get some fake ballots
self.fake_cast_ballot = ballot_factory.get_fake_ballot(
self.metadata, "some-unique-ballot-id-cast")
self.more_fake_ballots = []
for i in range(10):
self.more_fake_ballots.append(
ballot_factory.get_fake_ballot(
self.metadata, f"some-unique-ballot-id-cast{i}"))
self.fake_spoiled_ballot = ballot_factory.get_fake_ballot(
self.metadata, "some-unique-ballot-id-spoiled")
self.assertTrue(
self.fake_cast_ballot.is_valid(
self.metadata.ballot_styles[0].object_id))
self.assertTrue(
self.fake_spoiled_ballot.is_valid(
self.metadata.ballot_styles[0].object_id))
self.expected_plaintext_tally = accumulate_plaintext_ballots(
[self.fake_cast_ballot] + self.more_fake_ballots)
# Fill in the expected values with any missing selections
# that were not made on any ballots
selection_ids = set([
selection.object_id for contest in self.metadata.contests
for selection in contest.ballot_selections
])
missing_selection_ids = selection_ids.difference(
set(self.expected_plaintext_tally))
for id in missing_selection_ids:
self.expected_plaintext_tally[id] = 0
# Encrypt
encrypted_fake_cast_ballot = self.ballot_marking_device.encrypt(
self.fake_cast_ballot)
encrypted_fake_spoiled_ballot = self.ballot_marking_device.encrypt(
self.fake_spoiled_ballot)
self.assertIsNotNone(encrypted_fake_cast_ballot)
self.assertIsNotNone(encrypted_fake_spoiled_ballot)
self.assertTrue(
encrypted_fake_cast_ballot.is_valid_encryption(
self.context.crypto_extended_base_hash, self.joint_public_key))
# encrypt some more fake ballots
self.more_fake_encrypted_ballots = []
for fake_ballot in self.more_fake_ballots:
self.more_fake_encrypted_ballots.append(
self.ballot_marking_device.encrypt(fake_ballot))
# configure the ballot box
ballot_store = BallotStore()
ballot_box = BallotBox(self.metadata, self.context, ballot_store)
ballot_box.cast(encrypted_fake_cast_ballot)
ballot_box.spoil(encrypted_fake_spoiled_ballot)
# Cast some more fake ballots
for fake_ballot in self.more_fake_encrypted_ballots:
ballot_box.cast(fake_ballot)
# generate encrypted tally
self.ciphertext_tally = tally_ballots(ballot_store, self.metadata,
self.context)
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
)
