def hash_sbb(self, public):
""" Return a (tweaked) hash of the sbb contents. """
board = self.board
# next is commented out since we have no no-public posting
# in the current code.
if False:
if public:
board = [item for item in board if item[0][0] != "("]
board_str = sv.dumps(board)
hash_tweak = "hash_sbb"
return sv.secure_hash(board_str, hash_tweak, iterate=True)
def hash_sbb(self, public):
""" Return a (tweaked) hash of the sbb contents. """
board = self.board
# next is commented out since we have no no-public posting
# in the current code.
if False:
if public:
board = [item for item in board if item[0][0] != "("]
board_str = sv.dumps(board)
hash_tweak = "hash_sbb"
return sv.secure_hash(board_str, hash_tweak, iterate=True)
def hash_sbb(sbb, stop_before_header):
""" Return a (tweaked) hash of the sbb contents, including
all items up to (but not including) the item with header
equal to stop_before_header. (Copied from sv_prover.py)
"""
sbb_trunc = []
for item in sbb:
if item[0] == stop_before_header:
break
else:
sbb_trunc.append(item)
sbb_trunc_str = sv.dumps(sbb_trunc)
hash_tweak = "hash_sbb"
# use iterated hashing to slow down adversarial attack
return sv.secure_hash(sbb_trunc_str, hash_tweak, iterate=True)
def hash_sbb(sbb, stop_before_header):
""" Return a (tweaked) hash of the sbb contents, including
all items up to (but not including) the item with header
equal to stop_before_header. (Copied from sv_prover.py)
"""
sbb_trunc = []
for item in sbb:
if item[0] == stop_before_header:
break
else:
sbb_trunc.append(item)
sbb_trunc_str = sv.dumps(sbb_trunc)
#sv.dump([item for item in sbb_trunc if item[0]=='proof:output_commitments'], 'proof_output_commitments_VERIFIERVERSION.txt')
hash_tweak = "hash_sbb"
# use iterated hashing to slow down adversarial attack - change in sv_sbb.py as well
return sv.secure_hash(sbb_trunc_str, hash_tweak, iterate=False)
def hash_sbb(sbb, stop_before_header):
""" Return a (tweaked) hash of the sbb contents, including
all items up to (but not including) the item with header
equal to stop_before_header. (Copied from sv_prover.py)
"""
sbb_trunc = []
for item in sbb:
if item[0] == stop_before_header:
break
else:
sbb_trunc.append(item)
sbb_trunc_str = sv.dumps(sbb_trunc)
hash_tweak = "hash_sbb"
# use iterated hashing to slow down adversarial attack
return sv.secure_hash(sbb_trunc_str,
hash_tweak,
iterate=True)
def check_receipts(sbb_dict, db):
""" Check that receipts are consistent with cast vote commitments. """
receipt_ballot_ids = set(db['receipts'].keys())
cast_vote_dict = sbb_dict['casting:votes']['cast_vote_dict']
for race_id in cast_vote_dict:
for p in cast_vote_dict[race_id]:
d = dict()
for i in cast_vote_dict[race_id][p]:
ballot_id = cast_vote_dict[race_id][p][i]['ballot_id']
cu = cast_vote_dict[race_id][p][i]['cu']
cv = cast_vote_dict[race_id][p][i]['cv']
d[i] = {'cu': cu, 'cv': cv}
cv_receipt_data = [ballot_id, d]
cv_receipt_data_str = sv.dumps(cv_receipt_data)
cv_hash = sv.bytes2base64(sv.secure_hash(cv_receipt_data_str))
assert cv_hash == db['receipts'][ballot_id]['hash']
receipt_ballot_ids.remove(ballot_id)
assert len(receipt_ballot_ids) == 0
print("check_receipts: passed.")
def check_receipts(sbb_dict, db):
""" Check that receipts are consistent with cast vote commitments. """
receipt_ballot_ids = set(db['receipts'].keys())
cast_vote_dict = sbb_dict['casting:votes']['cast_vote_dict']
for race_id in cast_vote_dict:
for p in cast_vote_dict[race_id]:
d = dict()
for i in cast_vote_dict[race_id][p]:
ballot_id = cast_vote_dict[race_id][p][i]['ballot_id']
cu = cast_vote_dict[race_id][p][i]['cu']
cv = cast_vote_dict[race_id][p][i]['cv']
d[i] = {'cu': cu, 'cv': cv}
cv_receipt_data = [ballot_id, d]
cv_receipt_data_str = sv.dumps(cv_receipt_data)
cv_hash = sv.bytes2base64(sv.secure_hash(cv_receipt_data_str))
assert cv_hash == db['receipts'][ballot_id]['hash']
receipt_ballot_ids.remove(ballot_id)
assert len(receipt_ballot_ids) == 0
print("check_receipts: passed.")
def hash_sbb(self, public):
""" Return a (tweaked) hash of the sbb contents. """
board = self.board
# next is commented out since we have no no-public posting
# in the current code.
if False:
if public:
board = [item for item in board if item[0][0] != "("]
board_str = sv.dumps(board)
sbb_trunc = []
for item in board:
sbb_trunc.append(item)
board_str2 = sv.dumps(sbb_trunc)
#sv.dump([item for item in sbb_trunc if item[0]=='proof:output_commitments'], 'proof_output_commitments_SBBVERSION.txt')
assert board_str2 == board_str, "board_str2: " + board_str2 + " board_str: " + board_str
hash_tweak = "hash_sbb"
return sv.secure_hash(
board_str, hash_tweak, iterate=False
) # make iterate=True to slow down adversarial attacks change in sv_verifier.py as well
def cast_vote(self, race):
""" Cast random vote for this voter for this race in simulated election.
Of course, in a real election, choices come from voter via tablet.
"""
election = self.election
cvs = election.cast_votes
race_id = race.race_id
race_modulus = race.race_modulus
rand_name = self.rand_name
px = self.px
# cast random vote (for this simulation, it's random)
choice_str = race.random_choice() # returns a string
choice_int = race.choice_str2int(choice_str) # convert to integer
# ballot_id is random hex string of desired length
ballot_id_len = election.ballot_id_len
ballot_id = sv.bytes2hex(sv.get_random_from_source(rand_name))
ballot_id = ballot_id[:ballot_id_len]
assert len(ballot_id) == election.ballot_id_len
# secret-share choice
n = election.server.rows
t = election.server.threshold
share_list = sv.share(choice_int, n, t, rand_name, race_modulus)
# double-check that shares reconstruct to desired choice
assert choice_int == sv.lagrange(share_list, n, t, race_modulus)
# double-check that shares are have indices 1, 2, ..., n
assert all([share_list[i][0] == i + 1 for i in range(n)])
# then strip off indices, since they are equal to row number + 1
share_list = [share[1] for share in share_list]
# save ballots on election data structure
for row, x in enumerate(share_list):
(u, v) = sv.get_sv_pair(x, rand_name, race_modulus)
ru = sv.bytes2base64(sv.get_random_from_source(rand_name))
rv = sv.bytes2base64(sv.get_random_from_source(rand_name))
cu = sv.com(u, ru)
cv = sv.com(v, rv)
i = election.server.row_list[row]
vote = {
"ballot_id": ballot_id,
"x": x,
"u": u,
"v": v,
"ru": ru,
"rv": rv,
"cu": cu,
"cv": cv
}
cvs[race_id][px][i] = vote
# compute voter receipt as hash of her ballot_id and commitments
# note that voter gets a receipt for each race she votes in
receipt_data = [ballot_id]
d = dict()
for i in election.server.row_list:
cu = cvs[race_id][px][i]['cu']
cv = cvs[race_id][px][i]['cv']
d[i] = {'cu': cu, 'cv': cv}
receipt_data.append(d)
receipt_data_str = sv.dumps(receipt_data)
receipt_hash = sv.bytes2base64(sv.secure_hash(receipt_data_str))
self.receipts[ballot_id] = {'race_id': race_id, 'hash': receipt_hash}
