# File lib/paperclip/attachment.rb, line 288
    def hash_key(style_name = default_style)
      raise ArgumentError, "Unable to generate hash without :hash_secret" unless @options[:hash_secret]
      require 'openssl' unless defined?(OpenSSL)
      data = interpolate(@options[:hash_data], style_name)
      OpenSSL::HMAC.hexdigest(OpenSSL::Digest.const_get(@options[:hash_digest]).new, @options[:hash_secret], data)
    end