Sometimes you don’t want to encrypt all of your files. You just have some important data you’d like to keep protected, but your other files are not confidential at all and you don’t care if someone steals your Firefox bookmarks or your .procmailrc.
In those cases encrypting a whole disk or even a single partition might be too complicated (you don’t want to mess with partitions), or it could make your system too slow. There are other alternatives. A classical approach is to encrypt your important files using a tool like GnuPG. While this method works perfectly, it’s not the most convenient approach when you have, say, dozens of different files to encrypt.
EncFS is a cryptographic filesystem that transparently encrypts a whole directory tree. Data is always kept encrypted in a regular directory within an existing filesystem, and you have to mount that directory using EncFS in order to see its contents. Thus, once mounted, encrypted files can be accessed through this virtual filesystem just like any other file: you can edit, copy, rename and erase them just like you would do with any other file.
One of the main problems of EncFS is that each file stored maps to an encrypted file, so even though the file names and contents remain protected, anyone with access to your hard disk can see how many files you have, the directory structure, the metadata and even the approximate size of each file. If that’s not a problem for your needs, EncFS is a good piece of software and it’s very easy to install, set up and use.