def str_to_hash
        client = RestClient.where(:api_key => @http_headers[@@header_api_key]).first
        if client.nil?
          @errors << "client is not registered"
        end
        client.nil? ? "" : client.secret + @request_uri.gsub( /\?.*/, "" ) + @http_headers[@@header_timestamp]
      end
def str_to_hash
        client = RestClient.where(:api_key => @http_headers[@@header_api_key]).first
        if client.nil?
          @errors << "client is not registered"
        end
        client.nil? ? "" : client.secret + @request_uri.gsub( /\?.*/, "" ) + @http_headers[@@header_timestamp]
      end
generates the string that is hashed to produce the signature