# File lib/aws/core/signature/version_3_https.rb, line 25
        def add_authorization! credentials

          self.access_key_id = credentials.access_key_id

          parts = []
          parts << "AWS3-HTTPS AWSAccessKeyId=#{access_key_id}"
          parts << "Algorithm=HmacSHA256"
          parts << "Signature=#{signature(credentials)}"
          headers['x-amzn-authorization'] = parts.join(',')

          headers['x-amz-security-token'] = credentials.session_token if
            credentials.session_token

        end