MySQL AES Encryption for Ruby

my_sql_encryption.rb

require 'openssl'

# This module provides AES encryption compatible with MySQL AES_ENCRYPT
# and AES_DECRYPT functions.
module MySQLEncryption

  # Takes an unencrypted text string, encrypts it with the password,
  # and encodes the results to a hexadecimal string
  def self.mysql_encrypt(unencrypted_text, password)
    encrypt(unencrypted_text, mysql_key(password))
  end

  # Takes an encrypted, hex-encoded text string
  # and decrypts it with the password
  def self.mysql_decrypt(encrypted_hex, password)
    decrypt(encrypted_hex, mysql_key(password))
  end

  # Encode a binary value to hexadecimal
  def self.bin_to_hex(binary)
    binary.unpack('H*').first
  end

  # Decode a hex value into a binary
  def self.hex_to_bin(hex)
    hex.scan(/../).map {|digit| digit.hex}.pack('c*')
  end

  protected

  def self.aes(method, mysql_key, text)
    aes = OpenSSL::Cipher::Cipher.new('aes-128-ecb')
    aes.send(method)
    aes.key = mysql_key
    aes.update(text) << aes.final
  end

  def self.encrypt(unencrypted_text, mysql_key)
    bin_to_hex(aes(:encrypt, mysql_key, unencrypted_text))
  end

  def self.decrypt(encrypted_hex, mysql_key)
    aes(:decrypt, mysql_key, hex_to_bin(encrypted_hex))
  end

  def self.mysql_key(key)
    final_key = "\0" * 16
    key.length.times do |i|
      final_key[i % 16] = (final_key[i % 16].ord ^ key[i].ord).chr
    end
    final_key
  end

end