You have previously chosen which folders that should be shared.
If you want you can as well password protect the folders that you have shared.
When someone visits a folder that you have protected with a password
the visitor will see a login prompt. If the visitor has an account/password
(which you shall create above) he will get access to view the content of that folder.
Xerver uses a well-known secure one-way crypto, which by today has no known
decrypting algorithms.