# File lib/fog/storage/requests/aws/post_object_hidden_fields.rb, line 28
        def post_object_hidden_fields(options = {})
          if options['policy']
            options['policy'] = options['policy'].to_json
            options['AWSAccessKeyId'] = @aws_access_key_id
            string_to_sign = Base64.encode64(options['policy']).chomp!
            signed_string = @hmac.sign(string_to_sign)
            options['Signature'] = Base64.encode64(signed_string).chomp!
          end
          options
        end