fix_parity.py

#!/usr/bin/python

import argparse, sys

def hexdump(text, space=False):
    result = ""
    for t in text:
        s = str(hex(ord(t))).replace('0x', '')
        if len(s) == 1:
            s = '0' + s
        result = result + s
        if space:
            result = result + ' '
    return result

def fix_parity(key):
    byte_string = bin(int(key, 16))[2:]
    result = ""
    for offset in range(0, 56, 7):
        byte = byte_string[offset:offset+7]
        if byte.count('1') % 2 == 1:
            result = result + chr(int(byte + '0', 2))
        else:
            result = result + chr(int(byte + '1', 2))
    return result

def main():
    parser = argparse.ArgumentParser()
    parser.add_argument('key', help='kerberos key in hex format')
    args = parser.parse_args()

    result = fix_parity(args.key)
    print hexdump(result)

if __name__ == "__main__":
    main()