class MixNode(NetworkPart):
"""
The class mainly consists of:
- the key manager, whose keys are used to blind and un-blind messages/responses
- 3 cyclic group dual arrays (array + inverse) used to blind and un-blind messages
- the permutation array (self.perm) and its inverse (self.permInverse)
- the tuple (key share in cyclic group, exponent of key share): self.e
- the message components that the last node stores (forward and return): self.mixMessageComponents
- the decryption shares that every node computes (forward and return): self.decryptionShare
- the commitments (forward and return) of the last node stored by the other nodes: self.realMixCommitment
"""
def __init__(self, b):
NetworkPart.__init__(self)
self.sharedKey = None
self.b = b
self.r = CyclicGroupDualArray(self.b)
s = CyclicGroupDualArray(self.b)
s1 = CyclicGroupDualArray(self.b)
self.S = {'FOR': s, 'RET': s1}
perm = range(0, b)
shuffle(perm)
permInverse = inversePermute(perm)
self.permutation = {'FOR': perm, 'RET': permInverse}
self.e = CyclicGroup.randomPair()
self.mixMessageComponents = {'FOR': None, 'RET': None}
self.preMixCallback = {
'FOR': Callback.PRE_FOR_MIX,
'RET': Callback.PRE_RET_MIX
}
self.realMixCallback = {
'FOR': Callback.REAL_FOR_MIX,
'RET': Callback.REAL_RET_MIX
}
self.mixCommitCallback = {
'FOR': Callback.REAL_FOR_MIX_COMMIT,
'RET': Callback.REAL_RET_MIX_COMMIT
}
self.prePostProcessCallback = {
'FOR': Callback.PRE_FOR_POSTPROCESS,
'RET': Callback.PRE_RET_POSTPROCESS
}
self.realPostProcessCallback = {
'FOR': Callback.REAL_FOR_POSTPROCESS,
'RET': Callback.REAL_RET_POSTPROCESS
}
self.decryptionShare = {'FOR': None, 'RET': None}
self.realMixCommitment = {'FOR': None, 'RET': None}
self.senders = None
self.keyManager = KeyManager()
self.associateCallback(Callback.KEY_SHARE, self.storeSharedKey, 1)
self.associateCallback(Callback.PRE_FOR_MIX, self.preForwardMix, 1)
self.associateCallback(Callback.PRE_FOR_POSTPROCESS,
self.preForwardPostProcess, 1)
self.associateCallback(Callback.PRE_RET_MIX, self.preReturnMix, 1)
self.associateCallback(Callback.PRE_RET_POSTPROCESS,
self.preReturnPostProcess, 1)
self.associateCallback(Callback.KEY_USER, self.sendUserKey)
self.associateCallback(Callback.REAL_FOR_PREPROCESS,
self.realForPreProcess)
self.associateCallback(Callback.REAL_FOR_MIX, self.realForMix)
self.associateCallback(Callback.REAL_FOR_MIX_COMMIT,
self.realForMixCommit)
self.associateCallback(Callback.REAL_RET_MIX, self.realRetMix)
self.associateCallback(Callback.REAL_RET_MIX_COMMIT,
self.realRetMixCommit)
# called in network.init() before the precomputation phase, when the public key is collectively constructed
def computeSecretShare(self):
self.network.sendToNH(Message(Callback.KEY_SHARE, self.e[1]))
# store the above shared key (that the NH broadcasts)
def storeSharedKey(self, message):
self.sharedKey = message.payload
return Status.OK
# callback that performs dummy key exchange with a user
def sendUserKey(self, message):
userId = message.payload
self.keyManager.addSeeds(userId)
payload = [
self.id,
self.keyManager.getSeed(userId, KeyManager.MESSAGE),
self.keyManager.getSeed(userId, KeyManager.RESPONSE)
]
self.network.sendToUser(userId, Message(Callback.KEY_USER, payload))
return Status.OK
# called in network.init(), initiates the precomputation process
def precompute(self):
self.network.sendToNH(
Message(Callback.PRE_FOR_PREPROCESS,
self.r.inverse.encrypt(self.sharedKey).vector))
# callback that performs the mixing process in the the forward path of precomputation phase
def preForwardMix(self, message):
status = self.__preMix(message=ElGamalVector(vector=message.payload),
path='FOR')
# the last node initiates the matching return path
if self.__finalNode('FOR'):
self.network.sendToPreviousNode(
self.id,
Message(Callback.PRE_RET_MIX,
self.S['RET'].inverse.encrypt(self.sharedKey).vector))
return status
# callback that computes the decryption share of the forward path
def preForwardPostProcess(self, message):
return self.__prePostProcess(
randomComponents=CyclicGroupVector(vector=message.payload),
path='FOR')
# callback that performs mixing process in the the return path of precomputation phase
def preReturnMix(self, message):
return self.__preMix(message=ElGamalVector(vector=message.payload),
path='RET')
# callback that computes the decryption share of the return path
def preReturnPostProcess(self, message):
return self.__prePostProcess(
randomComponents=CyclicGroupVector(vector=message.payload),
path='RET')
# callback that computes the value that gradually replaces "keys" with "r" values in blind "messages"
def realForPreProcess(self, message):
self.senders = message.payload
cyclicVector = self.keyManager.getNextKeys(ids=self.senders,
type=KeyManager.MESSAGE,
inverse=False)
product = CyclicGroupVector.multiply(cyclicVector, self.r.array)
self.network.sendToNH(
Message(Callback.REAL_FOR_PREPROCESS, product.vector))
return Status.OK
# callback that performs the mixing process in the the forward path of real-time phase
def realForMix(self, message):
return self.__realMix(message=Vector(
vector=[CyclicGroupVector(vector=v) for v in message.payload]),
path='FOR')
# callback that performs the mixing process in the the return path of real-time phase
def realRetMix(self, message):
def tempProcess(temp):
return self.__returnPathKeyBlinding(temp)
return self.__realMix(message=Vector(
vector=[CyclicGroupVector(vector=v) for v in message.payload]),
path='RET',
tempProcess=tempProcess)
# callback that stores the commitment of the last node regarding
# the mixing process in the the forward path of real-time phase
def realForMixCommit(self, message):
def resultProcess(decrShare):
return decrShare
return self.__realMixCommit(message=Vector(
vector=[CyclicGroupVector(vector=v) for v in message.payload]),
path='FOR',
resultProcess=resultProcess)
# callback that stores the commitment of the last node regarding
# the mixing process in the the return path of real-time phase
def realRetMixCommit(self, message):
def resultProcess(decrShare):
return self.__returnPathKeyBlinding(decrShare)
return self.__realMixCommit(message=Vector(
vector=[CyclicGroupVector(vector=v) for v in message.payload]),
path='RET',
resultProcess=resultProcess)
# performs the mixing process of the precomputation phase
def __preMix(self, message, path):
result = ElGamalVector.multiply(
message.permute(self.permutation[path]),
self.S[path].inverse.encrypt(self.sharedKey))
if not self.__finalNode(path):
self.__toNextNode(
path, Message(self.preMixCallback[path], result.vector))
else:
self.mixMessageComponents[path] = result.messageComponents()
message = Message(self.prePostProcessCallback[path],
result.randomComponents().vector)
self.network.broadcastToNodes(self.id, message)
self.receive(message.toJSON())
return Status.OK
# performs the mixing process of the real-time phase
def __realMix(self, message, path, tempProcess=None):
temp = message.permute(self.permutation[path])
result = Vector([
CyclicGroupVector.scalarMultiply(temp.at(i),
self.S[path].array.at(i))
for i in range(0, self.b)
])
if not self.__finalNode(path):
self.__toNextNode(
path,
Message(self.realMixCallback[path],
[v.vector for v in result.vector]))
else:
self.network.broadcastToNodes(
self.id,
Message(self.mixCommitCallback[path],
[v.vector for v in result.vector]))
temp = CyclicGroupVector.multiply(self.decryptionShare[path],
self.mixMessageComponents[path])
if tempProcess is not None:
temp = tempProcess(temp)
result = Vector([
CyclicGroupVector.scalarMultiply(result.at(i), temp.at(i))
for i in range(0, self.b)
])
self.network.sendToNH(
Message(self.realPostProcessCallback[path],
[True, [v.vector for v in result.vector]]))
return Status.OK
# computes the decryption share
def __prePostProcess(self, randomComponents, path):
self.decryptionShare[path] = randomComponents.exp(self.e[0]).inverse()
return Status.OK
# the blinding proceess that the mix node performs in the return path (that involves user keys)
def __returnPathKeyBlinding(self, temp):
return CyclicGroupVector.multiply(
temp,
self.keyManager.getNextKeys(ids=self.senders,
type=KeyManager.RESPONSE,
inverse=False))
# stores the mixing commitment
def __realMixCommit(self, message, path, resultProcess):
self.realMixCommitment[path] = message
result = resultProcess(self.decryptionShare[path])
self.network.sendToNH(
Message(self.realPostProcessCallback[path],
[False, result.vector]))
return Status.OK
def __toNextNode(self, path, message):
if path == 'FOR':
return self.network.sendToNextNode(self.id, message)
elif path == 'RET':
return self.network.sendToPreviousNode(self.id, message)
else:
raise Exception("Wrong path!")
def __finalNode(self, path):
if path == 'FOR':
return self.network.isLastNode(self.id)
elif path == 'RET':
return self.network.isFirstNode(self.id)
else:
raise Exception("Wrong path!")
class User(NetworkPart):
"""
The class consists of:
- the key manager, whose keys are used to blind and un-blind messages/responses
- the response handler, that reads a message and produces a response
- the LAST message and response the user sent and received (or received and sent)
"""
def __init__(self, name, handler=None):
NetworkPart.__init__(self)
self.name = name
self.messageSent = None
self.messageGot = None
self.responseSent = None
self.responseGot = None
self.keyManager = KeyManager()
if handler is None:
self.setCallbackHandler(BasicHandler())
else:
self.setCallbackHandler(handler)
self.associateCallback(Callback.KEY_USER, self.storeKeyUser)
self.associateCallback(Callback.USER_MESSAGE, self.readMessage)
self.associateCallback(Callback.USER_MESSAGE_STATUS,
self.messageStatus)
self.associateCallback(Callback.USER_RESPONSE, self.readResponse)
# the key establishment takes place here
def setUp(self):
self.network.broadcastToNodes(self.id,
Message(Callback.KEY_USER, self.id))
def setCallbackHandler(self, callbackHandler):
self.callbackHandler = callbackHandler
# store the keys that a node sent
def storeKeyUser(self, message):
nodeId = message.payload[0]
messageKey = message.payload[1]
responseKey = message.payload[2]
self.keyManager.addSeeds(nodeId, (messageKey, responseKey))
self.callbackHandler.setUp(self)
return Status.OK
# send a message to a user through the mixnet
def sendMessage(self, userId, messageId, messageVector):
# store the message for future reference
self.messageSent = messageVector.copyVector()
# append the userId (the receiver)
# the NH will read this id (after the message is un-blinded) and route the message accordingly
messageVector.append(userId)
# blind the message with the combined key and send it to the NH
combinedKey = self.keyManager.getCombinedKey(type=KeyManager.MESSAGE,
inverse=True)
blindMessage = CyclicGroupVector.scalarMultiply(
messageVector, combinedKey)
self.network.sendToNH(
Message(Callback.USER_MESSAGE,
[self.id, messageId, blindMessage.vector]))
# read a message from the mixnet and send a response
def readMessage(self, message):
index = message.payload[0]
# the payload is the message (mapped to cyclic group members)
messageVector = CyclicGroupVector(vector=message.payload[1])
# compute a response and send it to the mixnet
responseVector = self.callbackHandler.messageHandler(
self, messageVector)
# store message and response for future reference
self.messageGot = messageVector.copyVector()
self.responseSent = responseVector.copyVector()
self.network.sendToNH(
Message(Callback.USER_RESPONSE, [index, responseVector.vector]))
return Status.OK
# read a response (after I sent a message)
def readResponse(self, message):
# un-blind the response and store it for future reference
responseVector = CyclicGroupVector.scalarMultiply(
CyclicGroupVector(vector=message.payload),
self.keyManager.getCombinedKey(type=KeyManager.RESPONSE,
inverse=True))
self.callbackHandler.responseHandler(self, responseVector)
self.responseGot = responseVector.copyVector()
return Status.OK
def messageStatus(self, message):
messageId = message.payload[0]
status = message.payload[1]
self.callbackHandler.messageStatusHandler(self, messageId, status)
return Status.OK
