AES-256-CBC encryption with 0 byte padding that works with mcrypt

gistfile1.rb

require 'openssl'

class Encryption
  attr_accessor :key

  IV_SIZE = 16

  def initialize(keycode)
    md5 = Digest::MD5.new
    md5.update(keycode)
    self.key = md5.hexdigest[0, IV_SIZE]
  end

  def encrypt(message)
    return nil if message.nil?
    iv = SecureRandom.random_bytes(IV_SIZE)
    aes = OpenSSL::Cipher.new('AES-128-CBC')
    aes.encrypt
    aes.padding = 0
    aes.key = key
    aes.iv = iv
    message = iv + message + ("\0" * (16 - (message.length % 16)))
    encrypted_data = aes.update(message) + aes.final
    CGI.escape(Base64.encode64(encrypted_data).strip)
  end

  def decrypt(encrypted_data)
    return nil if encrypted_data.nil?
    encrypted_data = Base64.decode64(encrypted_data)
    iv = SecureRandom.random_bytes(IV_SIZE)
    aes = OpenSSL::Cipher.new('AES-128-CBC')
    aes.decrypt
    aes.padding = 0
    aes.key = key
    aes.iv = iv
    message = (aes.update(encrypted_data) + aes.final)
    (message[16..-1]).gsub(/\x00/,'')
  end
end