The abrupt announcement that the widely used, anonymously authored disk-encryption tool Truecrypt is insecure and will no longer be maintained shocked the crypto world--after all, this was the tool Edward Snowden himself lectured on at a Cryptoparty in Hawai'i. Cory Doctorow tries to make sense of it all.

The Sourceforge project page for Truecrypt now sports a cryptographically signed notice that Truecrypt should no longer be used as it is not secure. The news came on the heels of a crowdfunded $70K security audit of the open source, anonymously maintained software giving it a relatively positive initial diagnosis. The announcement — signed by the same key that has been used to sign previous, legitimate updates — links Truecrypt's deprecation to Microsoft's decision to cease supporting Windows XP, though no one seems to have a theory about how these two facts relate to one another.

WARNING: Using TrueCrypt is not secure as it may contain unfixed security issues. This page exists only to help migrate existing data encrypted by TrueCrypt. The development of TrueCrypt was ended in 5/2014 after Microsoft terminated support of Windows XP. Windows 8/7/Vista and later offer integrated support for encrypted disks and virtual disk images. Such integrated support is also available on other platforms (click here for more information). You should migrate any data encrypted by TrueCrypt to encrypted disks or virtual disk images supported on your platform.

Truecrypt is a widely used system for disk-encryption, and is particularly noted for its "plausible deniability" feature, through which users can create hidden partitions within their cryptographic disks that only emerge if you enter the correct passphrase; this is meant to be a defense against "rubber hose cryptanalysis," in which someone is physically or legally threatened in order to coerce them into yielding up her keys. In the "plausible deniability" scenario, the victim can give up the keys to a "harmless" partition while keeping the very existence of a second partition for sensitive material a secret. I am a Truecrypt user, as, apparently, is Edward Snowden, who lectured on the software's use at a Cryptoparty he held in Hawai'i before going on the run.

The response to the Truecrypt news is mostly frank bafflement. The software is licensed under an obscure "open source" license that makes it unclear whether third parties can support the now (apparently) orphaned codebase.

Matthew Green, a Johns Hopkins University Information Security Institute crypto researcher, is the experts who led the fundraising in order to audit the Truecrypt source; in an interview with Brian Krebs, he says that he intends on continuing the work:

"There are a lot of things they could have done to make it easier for people to take over this code, including fixing the licensing situation," Green said. "But maybe what they did today makes that impossible. They set the whole thing on fire, and now maybe nobody is going to trust it because they'll think there's some big evil vulnerability in the code." Green acknowledged feeling conflicted about today's turn of events, and that he initially began the project thinking TrueCrypt was "really dangerous." "Today's events notwithstanding, I was starting to have warm and fuzzy feelings about the code, thinking [the developers] were just nice guys who didn't want their names out there," Green said. "But now this decision makes me feel like they're kind of unreliable. Also, I'm a little worried that the fact the we were doing an audit of the crypto might have made them decide to call it quits." Whether or not volunteer developers pick up and run with the TrueCrypt code to keep it going, Green said he's committed to finishing what he started with the code audit, if for no other reason than he's sitting on $30,000 raised for just that purpose.

The recent Heartbleed vulnerability demonstrated that even code that is widely used and widely examined can harbor long-lived critical bugs. As Green points out, the spectacular and mysterious blow-off from the anonymous Truecrypt team means that even if the code is given a clean bill of health from its auditors, it may be hard to convince people to trust it ever again.

Truecrypt's own warning suggests that users try Bitlocker, the proprietary Microsoft full-disk encryption tool that relies on the on-board Trusted Computing Module to attain a high degree of security. Microsoft itself has a deservedly poor reputation for standing up to government demands to weaken its products' security, but Peter Biddle, one of the architects of Trusted Computing and Bitlocker, has previously told me that he was repeatedly approached by frustrated federal agents who couldn't decrypt Bitlocker partitions, and I believe him, based on my personal knowledge of his character and work.

The free/open source world has some good solutions, like LUKS and dm-crypt, both of which come pre-installed on popular GNU/Linux versions like Ubuntu. The Ubuntu installer has a nice front-end to this stuff, allowing you the option of encrypting your whole disk while you install your OS.

In the meantime, the cause of the shutdown remains a mystery. This Reddit netsec thread is full of juicy speculation about the cause and suggestions for alternatives to Truecrypt.

I'd be interested in hearing your thoughts on alternatives to Truecrypt, and your overall data-security practices. Do you have a "plausible deniability" strategy for your own sensitive data?

-Cory Doctorow

(Image: Hard Drive 016, Jon Ross, CC-BY)