This value is a special name recognized by WSS4J to mean that the client certificate used to sign the request should be used to encrypt the response.
这个值是WSS4J能够识别的特殊名称，这表示应该使用请求签名所用的客户机证书对响应进行加密。
2
As a practical matter, except for special case situations using self-signed certificates and server to server communication, this makes certificate authentication infeasible.