Overview: elgamal is a python module that lets you encrypt and decrypt text using the ElGamal Cryptosystem.

Intended Use: This program was created as an exercise in cryptography in one of my classes at the University of Kentucky. I later turned it into a module. I do not recommend you use it to protect any sensitive information.

Using elgamal: Install elgamal by downloading elgamal.py and placing it in your module search path.

If you don't know your module search path, fire up a python console and run

import sys
sys.path

To use do

import elgamal

To generate a public/private key pair do

elgamal.generate_keys()
#returns a dictionary {'privateKey': privateKeyObject, 'publicKey': publicKeyObject}

By default generate_keys() generates a key of 256 bits with probability 0.9999999997671694 (1-(2^-32)) that your key is prime. You can alter the bitness of your keys and the certainty that your key is prime by passing arguments n and t like this.

elgamal.generate_keys(n, t)

where n is the number of bits you want your key to have and t means the probability that the key is prime is 1-(2^-t).

To encrypt a message do

cipher = elgamal.encrypt(publicKey, "This is the message I want to encrypt")
#returns a string

To decrypt the cipher text do

plaintext = elgamal.decrypt(privateKey, cipher)
#returns the message passed to elgamal.encrypt()

Compatibility: Python 3.4. Does not work in python 2.7!

License: MIT

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