This group is for security questions, so I'll answer this from the security side.
A passphrase is something unique that you'll have to type in and remember.
like... the quick brown fox jumped over the lazy arsed Linux admin
Then any encryption that might take place, will use this when generating your symmetric key pairs.
In Ctars case I think this is given to you once you buy it, or once you've filled in there evaluation form.
checkout
http://www.ctar.com/ctar/front.html
checkout
http://www.ctar.com/ctprice.html
/Raz