gistfile1.txt

This is a test file.
There are many like it.
But this test file is mine.

xor_defend.rb

#!/usr/bin/env ruby
require_relative 'xor_helper'

if ARGV.count < 2
  puts "Usage:  xor_defend [infile] [key]\n\n"
  exit
end

filename = ARGV[0]
key = ARGV[1]

begin
  file = File.read(filename)
  print XorHelper.encode(file, key)
rescue => e
  puts "Could not read file: #{e}"
end

## Example usage:
# ruby xor_defend.rb test.txt key > out.txt
# cat out.txt
# ruby xor_defend.rb out.txt key

xor_helper.rb

# Author: Clive Augustin, Tiffany Fontenelle-Augustin & Chen Li Zhan) 

# XorHelper provides an encode method to xor a file with a key
module XorHelper

  # XOR encodes/decodes a document with a key
  # Parameters:
  #   doc: string
  #   key: string
  # Returns: string
  def self.encode(doc, key)
    # Enter all your code into this method (only!)  
    # converts key and and doc to arrays   
    doc_array = doc.chars.map {|c| c}
    key_array = key.chars.map {|k| k}

    # key and doc zip together with rotating key
    doc_and_rotated_key = doc_array.zip(key_array.cycle)

    # Encryption or De-Encryption returned using xor :)
    return doc_and_rotated_key.map { |e,i| (e.ord ^ i.ord).chr}.join     
  end
end