[JDEV] Encryption on client - key on server

[Vladimirr]

                Hello all!
I would like to implement this encription schematic on our private jabber
based message
system, with Visual Basic client. Client uses encryption (twofish or
blowfish) with simmetric key.
It is possible to hardcode key into client exe file, but to be able changing
it from time to time,
I think it will be better to place it on jabber server and clients will get
it after authentication.
How it can be done? Through jabber.xml?
May be sombody successed in this?