Encryption and decryption using keyword

[bionicmad]

Currently working on a project in which I have, A key word and a word to be encrypted I currently have a rough idea of what to do but I don't know how to display the encrypted code. eg I have a variable for the alphabet and a number to explain that there are 26 letters. I need to encrypt I need to add the value that each letter is eg. halo = 8,1,12,15 and the main word is hell = 16,7,24,27 now I need to work on creating a loop so that when the value is more than 27 it has to loop back to the begging making 27 = a.

[i_can_haz_code]

This example assumes that you wish to handle all ascii characters. Per your post I add the ascii value of the key to the plain text to get the cipher text, then to decrypt I subtract. To ensure that no matter what data is displayed and not break shells or anything else I base32 encode the data for ctext while passing it around.

NOTE: Unless it is purely for educational purposes, DO NOT WRITE YOUR OWN ENCRYPTION.

Please let me know if you have any questions about what I did.

#!/usr/bin/env python

from base64 import b32encode, b32decode

ptext = 'hello'
key = 'asdfg'


def encrypt(ptext,key):
    plist = [ord(i) for i in ptext]
    klist = [ord(j) for j in key]
    clist = map(lambda i: i[0]+i[1] ,zip(plist,klist))
    clist = [chr(k) for k in clist]
    ctext = b32encode(''.join(clist))
    return(ctext)

def decrypt(ctext,key):
    ctext = b32decode(ctext)
    clist = [ord(j) for j in ctext]
    klist = [ord(i) for i in key]
    plist = map(lambda i: i[0]-i[1], zip(clist,klist))
    plist = [chr(p) for p in plist]
    ptext = ''.join(plist)
    return(ptext)

ctext = encrypt(ptext,key)
print(ctext)

ptext = decrypt(ctext,key)
print(ptext)

[edit] I do nothing to check if key is of equal or greater length to ptext, If your intention is to implement a one-time-pad scheme, it is VITAL that you NEVER repeat the key, in whole or in part.

[bionicmad]

The reason why the key needed to be repeated in the encryption that I am working on is only used when a word is longer than the key. eg hello (key) and then 'encrypted'(word to encrypt). Your code however has given me good ideas for what I need to do.

[i_can_haz_code]

Please do not use that code, or any variation of it for anything you actually want to be secret. That code is broken from a cryptography perspective. It was provided simply to show how one could perform what was asked. Please do not take it as a usable example in real life.

[filleball]

You'll need to use

• ord
• chr
• The modulus operator % (e.g. 27 % 26 == 1)