instance method _encrypt

# File activesupport/lib/active_support/message_encryptor.rb, line 169
      def _encrypt(value, **metadata_options)
        cipher = new_cipher
        cipher.encrypt
        cipher.key = @secret

        # Rely on OpenSSL for the initialization vector
        iv = cipher.random_iv
        cipher.auth_data = "" if aead_mode?

        encrypted_data = cipher.update(Messages::Metadata.wrap(@serializer.dump(value), **metadata_options))
        encrypted_data << cipher.final

        blob = "#{::Base64.strict_encode64 encrypted_data}--#{::Base64.strict_encode64 iv}"
        blob = "#{blob}--#{::Base64.strict_encode64 cipher.auth_tag}" if aead_mode?
        blob
      end