Quote from: PirateHatForTea on February 12, 2014, 10:02:44 PM

Quote from: MonkeeRench on February 12, 2014, 07:45:24 PM

...unless that is, in 2005 the NSA installed a PRNG backdoor in the AES-256 SHA-3 "NIST-approved" protocol for encryption, as Bruce Schneier et al. have shown long ago is highly probable.

Quote from: BruceSchneier link=url=https://www.schneier.com/blog/archives/2013/10/will_keccak_sha-3.html date=1380931200

I do not believe that the NIST changes were suggested by the NSA. Nor do I believe that the changes make the algorithm easier to break by the NSA. I believe NIST made the changes in good faith, and the result is a better security/performance trade-off. My problem with the changes isn't cryptographic, it's perceptual. There is so little trust in the NSA right now, and that mistrust is reflecting on NIST. I worry that the changed algorithm won't be accepted by an understandably skeptical security community, and that no one will use SHA-3 as a result.

So Schneier explicitly says he DOESN'T think there's a backdoor in SHA-3. WTF you talking about.

No, Schneier here was referring to the more recent NIST fumbling with the arguably inappropriate changes of the "winning" Keccak hash variation, not a backdoor. Schneier's far more serious concern has long been that expressed in "Did NSA Put a Secret Backdoor in New Encryption Standard?" by Bruce Schneier,  Wired News,  November 15, 2007:

"But one of those [NSA PNRG] generators -- the one based on elliptic curves -- is not like the others. Called Dual_EC_DRBG, not only is it a mouthful to say, it's also three orders of magnitude slower than its peers. It's in the standard only because it's been championed by the NSA, which first proposed it years ago in a related standardization project at the American National Standards Institute.

The NSA has always been intimately involved in U.S. cryptography standards -- it is, after all, expert in making and breaking secret codes. So the agency's participation in the NIST (the U.S. Commerce Department's National Institute of Standards and Technology) standard is not sinister in itself. It's only when you look under the hood at the NSA's contribution that questions arise.

Problems with Dual_EC_DRBG were first described in early 2006. The math is complicated, but the general point is that the random numbers it produces have a small bias. The problem isn't large enough to make the algorithm unusable -- and Appendix E of the NIST standard describes an optional work-around to avoid the issue -- but it's cause for concern. Cryptographers are a conservative bunch: We don't like to use algorithms that have even a whiff of a problem.

But today there's an even bigger stink brewing around Dual_EC_DRBG. In an informal presentation (.pdf) at the CRYPTO 2007 conference in August, Dan Shumow and Niels Ferguson showed that the algorithm contains a weakness that can only be described as a backdoor."

If Schneier et al. have ever changed their view on the PRNG Backdoor or expressed regret on their somewhat hedged probabilistic/weakness interpretations, I've never seen it in print and would appreciate any citation of such.

As Schneier has said, only a new Church Committee will ever reveal convincing truth and reform, and until such time it seems only fools use AES-256 without an open, proven, fully disclosed PRNG alternative to Dual_EC_DRBG (e.g.Twofish) and that it's possibly risky to use the NIST-Keccak hash variation rather than a similarly reliable hash, e.g. SKEIN.