Wait, what? TrueCrypt 'decrypted' by FBI to nail doc-stealing sysadmin

Do the Feds know something we don't about crypto-tool? Or did bloke squeal his password?

'It is difficult to understand what is meant by the decryption'

Talking to The Register, Kenn White, cofounder and co-director of the Open Crypto Audit Project – responsible for picking apart TrueCrypt's source code – said that it was important to remember when considering the testimony's diction that "decrypt just means unlock," and should not be taken as prima facie evidence that the FBI had broken TrueCrypt's cryptography.

"Without access to the sealed exhibits in this case, it is difficult to understand what is meant by 'decryption,'" White told us. "Supplying a known password is decrypting. Is retrieving data from a running, open encrypted disk volume 'decrypting'? We don't know."

Asked if it was too easy to overestimate the security provided by disk encryption in particular situations, such as when a volume is open on a running machine, White said: "Very much so." He added:

Even among technologists, this is a common misconception. An encrypted disk can either be inactive with the contents remaining confidential, or active and the data and credentials are in memory (and therefore able to be retrieved).

The security guarantees that TrueCrypt provides *only* hold for unmounted data. Which is, crucially, the same guarantees made by Microsoft BitLocker, Apple FileVault, and Linux DM-Crypt).

If an adversary can intercept keystrokes, access a mounted drive, or otherwise compromise a machine using disk or file encryption, very little can be done to protect that data.

Professor Anderson noted that there is too little information provided from which to presume that TrueCrypt was broken: "If the FBI or the Honduran police had a trojan installed on his PC during the lead-up to the bust, it would have snarfed the key, and it's also possible that he just used a weak key."

As for Glenn's "complex 30-character password," White told El Reg that "a strong, complex password implies that it is unlikely that the authorities were able to blindly brute-force the password from a TrueCrypt volume. See Jeremi Gosney's (slightly dated) recovery statistics using Brutalis, for example."

While detained ahead of his trial, Glenn made a phone call to his mother in which he asked her to relay a request to tell his housemate in Honduras "to disconnect the black box with the blinking lights on top of the batteries."

The prosecution states that this "black box" was the Synology storage device containing the TrueCrypt compartment with the stolen documents. It also alleges that "the reason [he] tried to send a message to [the housemate] to disconnect the black box is because he wanted to prevent law enforcement from discovering what the Synology contained."

"My impression ... was that Glenn was attempting to force-dismount the drive, making forensic recovery of the encrypted data far more difficult," said White.

Back in 2013, the FBI arrested Silk Road's Dread Pirate Roberts, legally known as Ross Ulbricht, in a public library in San Francisco. The Feds had patiently waited until he was already logged into his laptop, on which he was chatting to others as Dread Pirate Roberts – specifically to avoid the kind of situation Glenn may have been attempting to produce.

The agents were able to grab the laptop, which was using whole-disk encryption, while it was still logged in, allowing them to siphon off information.

"In the case of the Silk Roads arrest, the FBI agents went to fairly elaborate lengths to distract Ulbricht and to ensure that his laptop remained running and did not go into sleep mode or require screen unlock," White told us. "This would make forensic analysis much easier, both for memory and disk imaging and data recovery."

We may never know what the FBI managed to do. One witness's testimony in the case remains withheld from public on national security grounds. Keeping the methodology a secret may quite well be a bluff to scare people from TrueCrypt and similar tools. ®

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