# Tag Info

81

Edit: I have made some tests and I found something weird. See at the end. Initial answer: At least the Koblitz curves (K-163, K-233... in NIST terminology) cannot have been specially "cooked", since the whole process is quite transparent: Begin with a binary field $GF(2^m)$. For every m there is only one such field (you can have several representations, ...

51

I wouldn't try to explain the mathematics of the backdoor. Just explain that the NSA hid a secret backdoor in there. Instead, I would suggest focusing on the history and the context. For instance, you could explain about Crypto.AG, how they spiked their RNG to help the NSA spy on their customers. You could explain how random number generators are a ...

29

Your question is at least partially answered in FIPS 186-3 itself… Appendix A describes how to start with a seed and use an iterative process involving SHA-1 until a valid elliptic curve is found. Appendix D contains the NIST recommended curves and includes the seed used to generate each one according to the procedure in Appendix A. So to believe that NSA ...

23

Here is a list of products and companies who have had their EC DRBG algorithm validated by NIST. http://csrc.nist.gov/groups/STM/cavp/documents/drbg/drbgval.html The validation lists all modes that have been validated, so you can see which ones have gone to the effort of having their implementation of Dual_EC_DRBG validated. Tim Dierks points out that, for ...

23

The real question isn't "Why doesn't Suite B use P-521?" It is, "Why doesn't Suite B use AES-192?" NSA were only interested in 192-bit security for Suite B, but they chose to use AES-256 because AES-192 wasn't widely supported. "In fact we had wanted to use AES -128 and AES-192, but a quick survey of AES implementations (hardware centric, I believe) ...

22

First of all, there is a difference between writing to /dev/random and/or /dev/urandom and increasing the entropy count maintained in the Kernel. This is the reasony why, by default, /dev/random is world-writable - any input will only augment, but never replace the internal state of the RNG; if you write completely predictable data, you're doing no good, ...

22

RSA BSAFE Libraries (Both for Java and C/C++) use it as their default PRNG. Java: http://developer-content.emc.com/docs/rsashare/share_for_java/1.1/dev_guide/group__LEARNJSSE__RANDOM__ALGORITHM.html C/C++: https://community.emc.com/servlet/JiveServlet/previewBody/4950-102-2-17171/Share-C_1.1_rel_notes.pdf This obviously impacts users of the library such ...

19

Disclaimer: This post is possibly opinion based. How far ahead (if at all) are governmental agencies of open source (specifically academic) research? This question is impossible to answer. By definition, this require a knowledge of the state of research in such agencies which is definitively something they want to be kept as secret... thx to @fkraiem: ...

18

Frankly, I'd be surprised if anyone did use it. Even before the potential backdoor was discovered back in 2007, the Dual_EC_DRBG was known to be much slower and slightly more biased than all the other random number generators in NIST SP 800-90. To quote Bruce Schneier: "If this story leaves you confused, join the club. I don't understand why the NSA ...

18

The Government's elliptic curve backdoor is real, isn't it? We don't know for sure, but there are indicators into that direction. More importantly though, yes, you can backdoor the RNG, as was pointed out shortly after its publication (PDF) yes, the parameters have been replaced in-the-wild by attackers to break VPN appliances using this RNG. Does this ...

17

The standard in question was the Dual Elliptic Curve Deterministic Random Bit Generator (Dual_EC_DRBG), standardized in NIST Special Publication 800-90. In this case, it was not a protocol, but instead a random number generator. It wasn't exactly "broken"; instead, it was proven that there existed a "master key", if you will, that would allow someone to ...

13

Fundamentally, I do not believe you can compare them specifically because they tend to have different behaviors. I am an academic who does the non-classified work in conjunction with government teams; however, I'm not a cryptographer, but a circuit designer. I went from industry back to academia as a postdoc just to work in this space. I also don't have a ...

12

Since the rationale for the exclusion of P-521 and AES-192 is not explained, you can assume that either the curve is "too good" or that the cipher is "not good enough". The exclusion of SHA-512 implies a limit to 192-bit security for the standard, so AES-192 would be the logical choice. Its exclusion implies it is in someway not adequate for protecting TOP ...

12

What choice did they have? F1 is a bitwise function with three inputs and one output. There are $2^8 = 256$ such functions. Only 70 of them are "unbiased" (i.e. have as many 0 and 1 outputs in their image). If you further require that each input, as well as the order of inputs, matters for the output, you are left with only 36. However, those 36 are all ...

11

As of 9 Sep. 2013, the NIST recommendation is that Dual_EC_DRBG SHOULD NOT be used. Quoting from the link: Recommending against the use of SP 800-90A Dual Elliptic Curve Deterministic Random Bit Generation: NIST strongly recommends that, pending the resolution of the security concerns and the re-issuance of SP 800-90A, the Dual_EC_DRBG, as specified in ...

11

If the NSA knew a sufficiently large weak class of elliptic curves, it is possible for them to have chosen weak curves and have them standardized. As far as I can tell, there is no hint about any sufficiently large class of curves being weak. Regarding choosing the curves: It would have been better if NIST had used an "obvious" string as the seed, e.g. "...

11

Analyzable in this case means "simple to study". If your cipher consists of a small function that mixes a few things together, and then you repeat that often then your cipher is more easily understood and more easily fit into previous research knowledge than a overclomplicated large design. This is the case with Simon and Speck. Being easy to analyze is a ...

10

The September 2013 supplemental ITL bulletin released by NIST has drawn attention to NIST publication SP 800-90A, Random Number Generation using Deterministic Random Number Generation; specifically the trustworthiness of the Dual Elliptic Curve Deterministic Random Bit Generator (Dual EC DRBG) algorithm. As a result, NIST strongly discourages the use of ...

10

Most vulnerabilities in block ciphers are related to key security. Successful attacks have not been practical against anything except smaller keysizes than 256 bits or fewer rounds of encryption. Since there are no variables to be selected for AES except the S-box and the P-box, the Holy Grail is key management. Lateral attacks against AES rely on bad ...

9

Yes, it can: see http://people.umass.edu/gbecker/BeckerChes13.pdf [archived] for how to backdoor the bare metal without it being detectable by optical microscopes. On the other hand, adding Intel RDRAND output into a pool where it’s not the only entropy source is usually safe (always safe if it cannot dominate the output). That’s what is being discussed for ...

9

I don't think that rigging the xor instruction and possibly others would be as hard as lxgr suggests. What I would do if I were the hardware designer: add an extra bit to the output register of RDRAND. This bit means something like "unobserved". Until the user "opens the box" there could be anything in the register. (Think Schrodinger's Cat :-)) update XOR,...

9

Unfortunately you haven't made a scientific discovery. One of the places where large integer division is required is when testing for prime values. Primality tests are required to find real prime numbers within a set of candidate primes. So to find $p$ and $q$ large integer division is already required. That said, doing such a big calculation efficiently ...

8

For those who are wondering if Microsoft (being a big vendor) uses it… Windows does not use it. In fact, you must explicitly change from the default RNG which is AES-CTR RNG. Specifically: Debugging on Windows7 shows CryptGenRandom uses AES256-CTR with a 48 byte seed, which re-keys by XORing with its next 48 bytes output after each invocation to provide ...

8

Bernstein and Lange says that there has been no progress for prime-field elliptic curves since about 1999, when the NIST curves were chosen. No large class of weak curves were known then, and no large class is known now. Some small classes are known, (as Neves says) the curves with small embedding degree and the anomalous curves (order $n$ equals the prime $... 7 There is no such method. The only reliable way to "fix" a backdoored RNG is to mix its output with another, secure RNG. Specifically, let's consider a backdoor similar to that described by Becker et al. (2013), which essentially transforms the Intel TRNG into a deterministic PRNG using AES in OFB mode, with a 32-bit initial seed (occasionally reseeded) and ... 5 I've found this attack to be poorly documented, all-in-all. Below is a technical explanation of the matter, or one can skip to the conclusion if uninterested in the details. Dual_EC_DRBG First, let me give a short description of Dual_EC_DRBG using the notation of Shumow and Ferguson (see the presentation). As a preliminary, we are working with some prime-... 5 Assuming you manage to safely generate RSA keys which are sufficiently large, i.e. >= 2048 bits, no TLS configuration flaw on your side, and the lack of security bugs in the TLS library used by your server or the one used by the client user agent, I do not believe TLS_ECDH_RSA_WITH_AES_128_GCM can, at this point, be decrypted by surveillance agencies. Here'... 5 A length extension attack doesn't let you find a collision. It lets you predict the hash for an input with an unknown component in the prefix. If you have$h = H(x)$for unknown (or partially unknown)$x$, you can generate$h_y = H(x \vert\vert y)$for arbitrary$y\$ (this is not strictly correct; I've ignored padding, but for the purposes of this discussion ...

4

The way in which RDRAND's output is mixed into the /dev/random output buffers linux drivers/char/random.c, extract_buf() /* ... compute a hash.l[i] PRNG ... */ /* * If we have a architectural hardware random number * generator, mix that in, too. */ for (i = 0; i < LONGS(EXTRACT_SIZE); i++) { unsigned long v; ...

4

According to the BCryptGenRandom documentation The default random number provider implements an algorithm for generating random numbers that complies with the NIST SP800-90 standard, specifically the CTR_DRBG portion of that >standard. Specifically, according to this the default value is BCRYPT_RNG_ALGORITHM which is: The random-number generator ...

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