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HIKE.py
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HIKE.py
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from charm.toolbox.PKEnc import PKEnc
from charm.toolbox.ecgroup import G
from fastecdsa import ecdsa
import math
class HIKE(PKEnc):
def __init__(self, groupObj):
PKEnc.__init__(self)
global group
group = groupObj
self.isbyte = True
self.pp = self.setup()
def setup(self):
p = group.order()
curve = group
g = group.random(G)
return {'p':p,
'curve':curve,
'PRF': lambda msg,sk: group.init(value=ecdsa.sign(msg.decode('utf-8'), int(sk))[0]),
'g':g}
def keygen(self):
sk = group.random();
k = group.hash(group.random())
sk = {'sk': sk, 'k':k}
ek = self.pp
return (sk,ek)
def encrypt(self, sk, label, m):
l = self.extractLabel(label)
M = False
if (isinstance(m,bytes)):
M = group.encode(m)
elif (isinstance(m,int)):
self.isbyte = False
M = self.pp['g'] ** m
else:
raise Exception('Message should be either strings or numbers')
r = self.pp['PRF'](label,sk['k'])
ct = M * ((l['Q'] ** r) ** sk['sk'])
return {'ct': ct}
def generateLabel(self, sk, l, Q):
l0 = self.pp['g'] ** sk['sk']
tau = b"2:" + l
label = b"".join([group.serialize(l0), group.serialize(Q), tau])
return label
def extractLabel(self,label):
aux = label.decode("utf-8").split('2:')
tau = aux[1]
body = aux[0].split('1:')
l0 = group.deserialize(str.encode("1:"+body[1]))
Q = group.deserialize(str.encode("1:"+body[2]))
return {'l0':l0,
'Q':Q,
'tau':tau}
def publicKey(self, sk):
return self.pp['g'] ** sk['sk']
def tokenGen(self, sk, program):
f = program['f']
label = program['labels'][program['f'][0]]
tok = ((self.pp['g'] ** (self.pp['PRF'](label,sk['k'])-f[0])) ** sk['sk'])
return tok
def tokenDec(self, sk, ct, tok):
difference = tok ** sk['sk']
T = ct['ct'] / difference
M = False
if (self.isbyte):
M = group.decode(T)
else:
M = self.bruteforce(T)
return M
def eval(self, f, ciphertexts):
aggregated = self.pp['g'] ** 0
for idx,coeff in enumerate(f):
if idx>0:
aggregated *= (ciphertexts[idx-1]['ct']**f[idx])
else:
init = self.pp['g'] ** f[idx]
ct = init * aggregated
return {'ct': ct}
def destroyEnc(self,ct):
r = group.random()
ct['ct'] = ct['ct'] * (self.pp['g'] ** r)
return ct
def bruteforce(self, T):
a = 0
Q = self.pp['g'] ** a
b = math.sqrt(math.sqrt(int(self.pp['p'])))
while a <= b:
if Q == T:
return a
else:
a += 1
Q = Q * self.pp['g']
return "It is not in the index"
def decrypt(self, sk, program, ct):
partial_sum = 0
for idx,label in enumerate(program['labels']):
partial_sum += (self.pp['PRF'](label,sk['k']) * program['f'][idx+1])
label = program['labels'][program['f'][0]]
paramsLabel = self.extractLabel(label)
difference = (paramsLabel['Q'] ** partial_sum) ** sk['sk']
T = ct['ct'] / difference
M = False
if (self.isbyte):
M = group.decode(T)
else:
M = self.bruteforce(T)
return M
def testStringEncryption():
from charm.toolbox.eccurve import secp256k1
from charm.toolbox.ecgroup import ECGroup
groupObj = ECGroup(secp256k1)
hike = HIKE(groupObj)
(secret_key, eval_key) = hike.keygen()
(secret_key_prime, eval_key_prime) = hike.keygen()
msg = b"hello world!1234567891234567"
label = b"label1"
print('Public Key...')
Q = hike.publicKey(secret_key_prime)
print()
label = hike.generateLabel(secret_key, label, Q)
cipher_text = hike.encrypt(secret_key, label, msg)
program = {'f': [0,1],
'labels': [label]}
decrypted_msg = hike.decrypt(secret_key, program, cipher_text)
print("Decrypted message {}".format(decrypted_msg))
print()
tok = hike.tokenGen(secret_key, program)
msg = hike.tokenDec(secret_key_prime, cipher_text, tok)
print("TokenDec message {}".format(msg))
print()
print('Destroying ct....')
ct = hike.destroyEnc(cipher_text)
decrypted_msg = hike.decrypt(secret_key, program, ct)
print("Decrypted message {}".format(decrypted_msg))
print()
def testIntEncryption():
from charm.toolbox.eccurve import secp256k1
from charm.toolbox.ecgroup import ECGroup
groupObj = ECGroup(secp256k1)
hike = HIKE(groupObj)
(secret_key, eval_key) = hike.keygen()
(secret_key_prime, eval_key_prime) = hike.keygen()
msg = 10
label = b"label1"
print('Public Key...')
Q = hike.publicKey(secret_key_prime)
print()
label = hike.generateLabel(secret_key, label, Q)
cipher_text = hike.encrypt(secret_key, label, msg)
program = {'f': [0,1],
'labels': [label]}
decrypted_msg = hike.decrypt(secret_key, program, cipher_text)
print("Decrypted message {}".format(decrypted_msg))
print()
print('Eval...')
msg2 = 10
label2 = b"label2"
label2 = hike.generateLabel(secret_key, label2, Q)
program = {'f': [0, 1, 1],
'labels': [label,label2]}
cipher_text2 = hike.encrypt(secret_key, label2, msg2)
cipher_text_eval = hike.eval(program['f'], [cipher_text,cipher_text2])
decrypted_msg = hike.decrypt(secret_key, program, cipher_text_eval)
print("Decrypted message eval f(0,1,1) and msg[1,1]: {}".format(decrypted_msg))
print()
print('Token Gen...')
tok = hike.tokenGen(secret_key, program)
print()
print('Token Dec...')
tokenDec = hike.tokenDec(secret_key_prime, cipher_text, tok)
print("TokenDec message {}".format(tokenDec))
print()
print('ct: {}'.format(cipher_text['ct']))
print('Destroying ct....')
ct = hike.destroyEnc(cipher_text)
print('ct: {}'.format(ct['ct']))
if __name__ == "__main__":
testStringEncryption()
testIntEncryption()