def do_start(self, config):
'''
this is called by the protocol when we receive a command from the TS
to start a new collection phase
return None if failure, otherwise the protocol will encode the result
in json and send it back to TS
'''
logging.info("got command to start new collection phase")
# keep the start config to send to the TS at the end of the collection
# deepcopy so we can delete the (encrypted) secrets from the shares
self.start_config = deepcopy(config)
# discard the secrets
# we haven't checked if any shares are present, so don't assume
for share in self.start_config.get('shares', []):
# this is still encrypted, so there's no need for a secure delete
del share['secret']
share['secret'] = "(encrypted blinding share, deleted by share keeper)"
# sort the shares, so that their order is consistent between rounds
self.start_config.get('shares', []).sort()
if ('shares' not in config):
logging.warning("start command from tally server cannot be completed due to missing shares")
return None
combined_counters = self.check_start_config(config)
if combined_counters is None:
return None
else:
config['counters'] = combined_counters
self.keystore = SecureCounters(config['counters'], counter_modulus())
share_list = config['shares']
private_key = load_private_key_file(self.config['key'])
for share in share_list:
encrypted_secret = share['secret']
secret = decrypt(private_key, encrypted_secret)
# TODO: secure delete
share['secret'] = secret
blinding_result = self.keystore.import_blinding_share(share)
if not blinding_result:
# the structure of the imported share did not match the
# configured counters
# this is likely a configuration error or a programming bug,
# but there is also no way to detect the TS modifying the data
logging.warning("failed to import blinding share {} config {}"
.format(share, config))
# TODO: secure delete
del private_key
return None
logging.info("successfully started and imported {} blinding shares for {} counters ({} bins)"
.format(len(share_list), len(config['counters']), count_bins(config['counters'])))
# TODO: secure delete
del private_key
return {}
def check_encdec(pub_key, priv_key, data_structure):
"""
Check that data_structure survives encryption and descryption intact
"""
logging.debug("Encrypting data structure:")
ciphertext = encrypt(pub_key, data_structure)
logging.debug("Decrypting data structure:")
result_structure = decrypt(priv_key, ciphertext)
check_equality(data_structure, result_structure)
logging.debug("Decrypted data was identical to the original data!")