def get_hamilton_election_with_encryption_context(
self, ) -> Tuple[AllPublicElectionData, AllPrivateElectionData]:
guardians: List[Guardian] = []
coefficient_validation_sets: List[CoefficientValidationSet] = []
# Configure the election builder
description = self.get_hamilton_election_from_file()
builder = ElectionBuilder(NUMBER_OF_GUARDIANS, QUORUM, description)
# Setup Guardians
for i in range(NUMBER_OF_GUARDIANS):
guardians.append(
Guardian(
"hamilton-county-canvass-board-member-" + str(i),
i,
NUMBER_OF_GUARDIANS,
QUORUM,
))
# Run the key ceremony
mediator = KeyCeremonyMediator(guardians[0].ceremony_details)
for guardian in guardians:
mediator.announce(guardian)
mediator.orchestrate()
mediator.verify()
# Joint Key
joint_key = mediator.publish_joint_key()
# Save Validation Keys
for guardian in guardians:
coefficient_validation_sets.append(
guardian.share_coefficient_validation_set())
builder.set_public_key(get_optional(joint_key).joint_public_key)
builder.set_commitment_hash(get_optional(joint_key).commitment_hash)
metadata, context = get_optional(builder.build())
constants = ElectionConstants()
return (
AllPublicElectionData(description, metadata, context, constants,
coefficient_validation_sets),
AllPrivateElectionData(guardians),
)
class ElectionGuardTestClient:
def __init__(self, manifest_file: str, manifest_path: str, guardians: int,
quorom: int):
self.NUMBER_OF_GUARDIANS = guardians
self.QUORUM = quorom
self.manifest_path = manifest_path
self.manifest_file = manifest_file
self.guardians: List[Guardian] = []
self.key_ceremony_mediator = KeyCeremonyMediator(
CeremonyDetails(self.NUMBER_OF_GUARDIANS, self.QUORUM))
def setupGuardians(self):
# 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_mediator.announce(guardian)
def setupKeyCeromony(self):
self.setupGuardians()
self.key_ceremony_mediator.orchestrate(identity_auxiliary_encrypt)
self.verification_results = self.key_ceremony_mediator.verify(
identity_auxiliary_decrypt)
self.joint_public_key = self.key_ceremony_mediator.publish_joint_key()
def setupElectionBuilder(self):
# 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.
with open(os.path.join(self.manifest_path, self.manifest_file),
"r") as manifest:
string_representation = manifest.read()
election_description = ElectionDescription.from_json(
string_representation)
builder = ElectionBuilder(
number_of_guardians=self.
NUMBER_OF_GUARDIANS, # since we will generate a single public-private keypair, we set this to 1
quorum=self.
QUORUM, # since we will generate a single public-private keypair, we set this to 1
description=election_description)
builder.set_public_key(self.joint_public_key)
self.metadata, self.context = get_optional(builder.build())
self.builder = builder
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 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)
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
