Encryption with a key known to both parties

Hi Folks,

Is it possible to express "Scenario #4 Session Key" (the client and the
service uses a random symmetric key that has been previously agreed)
described in this [1] document with WS-SecurityPolicy?

I guess we should use SymmetricBinding but how can we express the
Protection/EncryptionToken?

Thanks,
Ruchith

1.
http://svn.apache.org/repos/asf/webservices/wss4j/trunk/specs/wss-interop2-draft-06.pdf