Little Security

[Stephen ODonnell]

Hi,

I have a mobile phone app which sends an xml file containing a 'username\password' pair to a web service. I need to encrypt the password before it is sent, then decrypt it on the web service and store it in a database.

What is the most efficient way of going about this task?

I need the encrypted password to be dynamic, therefore I could create a dynamic key. I also need to use symmetric cipher(for speed).

Is PBE suitable, secure enough?
I could create the key, on the mobile app side, and send it as part of the xml file.

I'm new to encryption, so any help greatly appreciated.
Thanks,
Stephen