CryptoFS is a encrypted filesystem for Filesystem in Userspace (FUSE) and the Linux Userland FileSystem (LUFS). CryptoFS will use a normal directory to store files encrypted. The mountpoint will contain the decrypted files. Every file stored in this mountpoint will be written encrypted (data and filename) to the directory that was mounted. If you unmount the directory the encrypted data can only be access by mounting the directory with the correct key again. Like other FUSE/LUFS filesystems it does not need root access or any complicated setup like creating a filesystem on a encrypted disk using the loop device. This requires fuse (also available at SlackBuilds.org), although it can alternatively use LUFS if you have that installed from elsewhere.