Python/ciphers/elgamal_key_generator.py

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import os
import random
import sys
import rabin_miller as rabinMiller, cryptomath_module as cryptoMath
min_primitive_root = 3
def main():
print('Making key files...')
makeKeyFiles('elgamal', 2048)
print('Key files generation successful')
# I have written my code naively same as definition of primitive root
# however every time I run this program, memory exceeded...
# so I used 4.80 Algorithm in Handbook of Applied Cryptography(CRC Press, ISBN : 0-8493-8523-7, October 1996)
# and it seems to run nicely!
def primitiveRoot(p_val):
print("Generating primitive root of p")
while True:
g = random.randrange(3,p_val)
if pow(g, 2, p_val) == 1:
continue
if pow(g, p_val, p_val) == 1:
continue
return g
def generateKey(keySize):
print('Generating prime p...')
p = rabinMiller.generateLargePrime(keySize) # select large prime number.
e_1 = primitiveRoot(p) # one primitive root on modulo p.
d = random.randrange(3, p) # private_key -> have to be greater than 2 for safety.
e_2 = cryptoMath.findModInverse(pow(e_1, d, p), p)
publicKey = (keySize, e_1, e_2, p)
privateKey = (keySize, d)
return publicKey, privateKey
def makeKeyFiles(name, keySize):
if os.path.exists('%s_pubkey.txt' % name) or os.path.exists('%s_privkey.txt' % name):
print('\nWARNING:')
print('"%s_pubkey.txt" or "%s_privkey.txt" already exists. \n'
'Use a different name or delete these files and re-run this program.' %
(name, name))
sys.exit()
publicKey, privateKey = generateKey(keySize)
print('\nWriting public key to file %s_pubkey.txt...' % name)
with open('%s_pubkey.txt' % name, 'w') as fo:
fo.write('%d,%d,%d,%d' % (publicKey[0], publicKey[1], publicKey[2], publicKey[3]))
print('Writing private key to file %s_privkey.txt...' % name)
with open('%s_privkey.txt' % name, 'w') as fo:
fo.write('%d,%d' % (privateKey[0], privateKey[1]))
if __name__ == '__main__':
main()