The Username Authentication with Symmetric Keys mechanism protects your application for integrity and confidentiality. Symmetric key cryptography relies on a single, shared secret key that is used to both sign and encrypt a message. Symmetric keys are usually faster than public key cryptography.
For this mechanism, the client does not possess any certificate/key of his own, but instead sends its username/password for authentication. The client shares a secret key with the server. The shared, symmetric key is generated at runtime and encrypted using the service’s certificate. The client must specify the alias in the truststore by identifying the server’s certificate alias.