This encryption applies only to client/server authentication - not peer-to-peer authentication.
You need to specify the name of a valid symmetric key cipher supported by the JDK. Valid key names, like DES, DESede, AES, and Blowfish, enable the Diffie-Hellman algorithm with the specified cipher to encrypt the credentials. For valid JDK names, see http://download.oracle.com/javase/1.5.0/docs/guide/security/CryptoSpec.html#AppA.