RC4 No Swap

RC4-no-swap.py

#!/usr/bin/env python

debug = 0

def KSA(key):
    keylength = len(key)

    if debug == 1:
        print("Current Keylength is " + str(keylength))

    S = range(256)

    j = 0
    for i in range(256):
        j = (j + S[i] + key[i % keylength]) % 256
        if debug == 1: 
            print("Before Swap i is set to: " + str(i) + " and j is currently: " + str(j))

        #
        # Let's remove swapping as a test for the special no swap thing
        #
        #S[i], S[j] = S[j], S[i]  # swap

        if debug == 1: 
            print("Now swap, Si is: " + str(S[i]) + " and Sj is: " + str(S[j]))
    if debug == 1:
        print("Will return S which is: " + str(S))
    return S


def PRGA(S):
    i = 0
    j = 0
    while True:
        if debug == 1:
            print("Currently i is: " + str(i) + " and j is: " + str(j))
        i = (i + 1) % 256
        j = (j + S[i]) % 256

        #
        # Let's remove the swapping as a test for the special no swap thing
        #S[i], S[j] = S[j], S[i]  # swap

        K = S[(S[i] + S[j]) % 256]
        yield K


def RC4(key):
    S = KSA(key)
    return PRGA(S)


if __name__ == '__main__':
    key = 'Key'
    plaintext = 'Plaintext'

    def convert_key(s):
        if debug == 1:
            print("The Key here is set to: " + str(key))
        return [ord(c) for c in s]

    key = convert_key(key)
    if debug == 1:
        print("We will now convert the key to oridinals of each value, key is now" + str(key))

    keystream = RC4(key)

    import sys
    for c in plaintext:
        sys.stdout.write("%02X" % (ord(c) ^ keystream.next()))
    print