SANS ISC: True Crypt Compromised / Removed?

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Earlier today, the popular disk encryption tool Truecrypt was essentially removed from Sourceforge, and replaced with a warning that Truecrypt is no longer secure and people should switch to Bitlocker  (with instructions as to how to do this). The source code was updated and essentially all functionality was removed but the installer will now just show a message similar to the one displayed on the homepage.

What you probably are asking first about: What does this mean for me if I use Truecrypt?

At this point, there are many rumors, and few facts. It is my recommendation (as always) to stay calm. One thing you want to do right away: Get a copy of the last working version and burn it to CD (actually: 3 CDs) in case it is no longer available and you need to access offline media that are encrypted using Truecrypt. Find out what your alternatives are. In Windows you have Bitlocker, in OS X you got FileVault and in Linux you got LUKS. Sadly, these are not compatible with each other. You will need to find a replacement for portable media that need to move between operating systems. PGP/GnuPG comes to mind as an option. 

Now back to what we know so far:

Recently, a community effort was launched to review the Truecrypt code, in particular to check for backdoors and incorrectly implemented crypto algorithms. As far as I know, no significant issue was found to date.

This very much smells to me like a compromised Sourceforge repository. Truecrypt uses Sourceforge for all of its content. At this point, sit back, don't visit the Truecrypt Sourceforge page or download the crippled version, but don't panic (yet).

But, via twitter and e-mail, some additional disturbing facts came in that make this look worse then a simple web site compromise:

• The new "decrypt only" binary was signed with what looks like a valid Truecrypt code signing key (I believe GRC.com investigated this)
• The PGP signature was valid as well
• The Truecrypt development team is anonymous, and so far, no word if the code review team was able to reach them.

Correction about the earlier note that Sourceforge was compromised: Turns out that they asked users to change passwords NOT because of a compromise, but because they changed the hashing algorithm.

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Johannes B. Ullrich, Ph.D.
SANS Technology Institute
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