Tinfoil Hat Linux (THL) is a compact Security-focusedLinux distribution designed for high security developed by the Shmoo Group. The first version (1.000) was released in February 2002. It appears to be a low priority project as of 2013[update]. Its image files and source are available in gzip format. THL can be used on almost any modern PC, as it requires a Intel 80386 or better computer, with at least 8 MB of RAM. The distribution fits on a single HD floppy. The small footprint provides additional benefits beyond making the system easy to understand and verify- the computer need not even have a hard drive, making it easier to "sanitize" the computer after use.
The logo of Tinfoil Hat is Tux, the Linux mascot, wearing a tinfoil hat.
Data retrieval — All temporary files are created on an encrypted ramdisk that is destroyed on shutdown. Even the GPG keyfile information can be stored encrypted on the floppy.
Keystroke monitoring — THL has gpggrid, a wrapper for GPG that lets you use a video game style character entry system instead of typing in your passphrase. Keystroke loggers get a set of grid points, not your passphrase.
Power usage and other side channel attacks — Under the Paranoid options, a copy of GPG runs in the background generating keys and encrypting random documents. This makes it harder to determine when real encryption is taking place.
An advantage of THL is that it can be used on virtually any modern PC using the x86 processor architecture. For example, one might install it on a computer that is kept in a locked room, not connected to any network, and used only for cryptographically signing keys. While the paranoid mode security measures may seem over the top and might be found funny, they are a good education in the types of issues that must be considered for high security. It is fairly easy to create the Tinfoil Hat booting floppy with Microsoft Windows. Verifying the checksum can be more tricky. The text of the documentation is salted with just a few jokes, which reinforces their humor by the stark contrast with the serious and paranoiac tone of the surrounding text- the very name pokes fun at itself, as Tinfoil hats are commonly ascribed to paranoiacs as a method of protecting oneself from mind-control waves.
Tinfoil Hat Linux requires one to work in a text-only environment in Linux, i.e. starting straight off with a Bourne shell and the editor vi, not a graphical user interface. It uses BusyBox instead of the normal util-linux, the GNU coreutils (formerly known as fileutils, shellutils and textutils) and other common Unix tools. Tinfoil Hat also offers the nano text editor.