unblind.py

from Crypto.PublicKey import RSA
from Crypto.Hash import SHA256
from random import SystemRandom

import sys


print("Start")



def readFromFile(filename):
    file = open(filename, 'r')
    data = file.readlines()
    file.close()
    return ''.join(data).replace(">","").replace("<","")


pub= RSA.importKey(readFromFile('key.pub'))


r = (long) (readFromFile('r'))

msg_blinded_signature = long(sys.argv[1])


print pub.exportKey()
print "r:" , r
print "blinded signature: " , msg_blinded_signature

#SA computes
# msg_blinded_signature = ''.join(str(bytearray.fromhex(msg_blinded_signature)))

# user computes
msg_signature = pub.unblind(msg_blinded_signature, r)

print "Signature for original ballot:"
print msg_signature

msg = raw_input("What was the original ballot? ")
print "got: " + msg



# Someone verifies
hash = SHA256.new()
hash.update(msg)
msgDigest = hash.hexdigest()

if (pub.verify(msgDigest, (msg_signature,))):
    print "Signature is good. Submit signature and original ballot to the counter"
else:
    print "The signature is invalid. Something went wrong"