TrueCrypt audit back on track after silence and uncertainty

An effort to search for cryptographic flaws in TrueCrypt, a popular disk encryption program, will resume even though the software was abandoned by its creators almost a year ago.

For years TrueCrypt has been the go-to open-source tool for people looking to encrypt files on their computers, especially since it’s one of the few solutions to allow encrypting the OS volume.

In October 2013, cryptography professor Matthew Green and security researcher Kenneth White launched a project to perform a professional security audit of TrueCrypt. This was partly prompted by the leaks from former U.S. National Security Agency contractor Edward Snowden that suggested the NSA was engaged in efforts to undermine encryption.

Green and White’s Open Crypto Audit Project started accepting donations and contracted iSEC Partners, a subsidiary of information assurance company NCC Group, to probe critical parts of the TrueCrypt code for software vulnerabilities. The firm found some issues, but nothing critical that could be described as a backdoor. Their report, published in April 2014, covered the first phase of the audit.

Phase two was supposed to involve a formal review of the program’s encryption functions, with the goal of uncovering any potential errors in the cryptographic implementations — but then the unexpected happened.

In May 2014, the developers of TrueCrypt, who had remained anonymous over the years for privacy reasons, abruptly announced that they were discontinuing the project and advised users to switch to alternatives.

“This threw our plans for a loop,” Green said in a blog post Tuesday. “We had been planning a crowdsourced audit to be run by Thomas Ptacek and some others. However in the wake of TC pulling the plug, there were questions: Was this a good use of folks’ time and resources? What about applying those resources to the new ‘Truecrypt forks’ that have sprung up (or are being developed?)”

Now, almost a year later, the project is back on track. Ptacek, a cryptography expert and founder of Matasano Security, will no longer lead the cryptanalysis and the effort will no longer be crowdsourced. Instead, phase two of the audit will be handled by Cryptography Services, a team of consultants from iSEC Partners, Matasano, Intrepidus Group, and NCC Group.

The cost of professional crypto audits is usually very high, exceeding the US$70,000 the Open Crypto Audit Project raised through crowdfunding. To keep the price down, the project had to be flexible with its time frame and work around Cryptography Services’ other engagements.

“The project will evaluate the original Truecrypt 7.1a which serves as a baseline for the newer forks, and it will begin shortly,” Green said. “However to minimize price — and make your donations stretch farther — we allowed the start date to be a bit flexible, which is why we don’t have results yet.”

Over the past year, while deciding on how to proceed, the Open Crypto Audit Project members looked at some parts of the TrueCrypt cryptographic code themselves, including the program’s random number generator.

“This will hopefully complement the NCC/iSEC work and offer a bit more confidence in the implementation,” Green said.

The Cryptography Services audit will focus on Truecrypt-encrypted containers at rest, which is what many people use the software for: creating encrypted containers which they then mount and store data in.

“We want to be sure that the cryptography used to protect these encrypted volumes is solid and free of any errors that could allow recovery of the data,” the Cryptography Services team said in a blog post. “Because of the nature of the work, we’ll be focusing on the mode widely used and standardized components: XTS mode used with AES, as well as the Double and Triple Compositions.”