gistfile1.rb

#!/usr/bin/env ruby
# -*- coding: utf-8 -*-

require 'base64'
require 'digest'
require 'openssl'

def encode(cryptkey, iv, cleardata)
  cipher = OpenSSL::Cipher.new('AES-256-CBC')
  cipher.encrypt
  cipher.key = cryptkey
  cipher.iv  = iv
  
  encrypted = ''
  encrypted << cipher.update(cleardata)
  encrypted << cipher.final
  encrypted
end

def decode(cryptkey, iv, secretdata)
  cipher = OpenSSL::Cipher.new('AES-256-CBC')
  cipher.decrypt
  cipher.key = cryptkey
  cipher.iv  = iv
  
  decrypted = ''
  decrypted << cipher.update(secretdata)
  decrypted << cipher.final
  decrypted
end

def flipByte(original, index)
  bytes = original.unpack("C*")
  bytes[index] ^= 0xff
  bytes.pack("C*")
end

cryptkey = Digest::SHA256.digest('Nixnogen')
iv       = 'a2xhcgAAAAAAAAAA'
buf      = "Here is some data for the coding" # 32 chars
enc      = encode(cryptkey, iv, buf)


puts "Encoded length: #{enc.length}"
puts "Encoded in hex: " + enc.unpack("H*").first
puts "Decode original " + decode(cryptkey, iv, enc)

enc = flipByte(enc, 31)
puts "Encoded in hex: " + enc.unpack("H*").first
puts "Decode original " + decode(cryptkey, iv, enc)