decrypt (ActiveSupport::MessageEncryptor)

    # File lib/active_support/message_encryptor.rb, line 35
        def decrypt(encrypted_message)
          cipher = new_cipher
          encrypted_data, iv = encrypted_message.split("--").map {|v| ActiveSupport::Base64.decode64(v)}

          cipher.decrypt
          cipher.key = @secret
          cipher.iv  = iv

          decrypted_data = cipher.update(encrypted_data)
          decrypted_data << cipher.final

          Marshal.load(decrypted_data)
        rescue OpenSSLCipherError, TypeError
          raise InvalidMessage
        end