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# Tag Info

25

Is this number specified anywhere? It was formally specified in this RFC as the 1536 bit MODP group (although its use predates that RFC). However, from what I've seen, the 2048 bit MODP group from that same document is actually more popular. Why was this particular number picked? Well, it's a safe prime; in addition, the leading 64 bits and the ...

25

When NIST introduced SHA-0 in 1993, they – for the first time – switched their naming convention from MD-n to SHA-n Actually, MD-n was not NIST's naming conventions; it was RSA Security's (a private company) naming convention. Before SHA (which was the original name; SHA-0 is retroactive terminology given to distinguish the original proposal from what was ...

23

It seems that PGP certificates have the problem that they can be changed by the user. Furthermore, there were extensions for 1.2 that are incompatible for 1.3 (if they were secure in the first place): I found this on the TLS mailing list from Ilari Liusvaara: Ugh, the situation is way worse than what I thought. Basically, all three assume they have ...

22

At the time of the competition (I can talk about it, I was there), there was a lot of discussion and various people showed arguments. However, there was never an official, publicly known "board of scores" with totals and definite rules, as the pictures you show seem to purport. It is possible that the NIST people did make something similar internally, but ...

20

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) ...

20

I would characterize the service as similar to a trusted time-stamping service. Except they do not do the time-stamping, but just provide the "key". This allows a user to decide what do to with it, such as using it as a private key to sign something, or an HMAC key, proving the signature is "not older" than the timestamp. If the signature is published to a ...

18

If you find a flaw or bug for example in Linux kernel you can create an issue in GitHub, or if you can solve it you can contribute. How about Finding a flaw in cryptographic protocol?! A protocol is slightly different than a concrete implementation of a piece of software like the linux kernel on GitHub. It is closer to a specification that may be followed ...

16

I'm not aware of any official NIST policy on the matter, so I can only make educated guesses. I guess new algorithms have sprung up and are already in place. ChaCha20 is used in TLS 1.2 and 1.3. For hash functions, neither SHA-2 nor SHA-3 are depending on AES in any way. The sponge function in Keccak (SHA-3) can also be used as a symmetric cipher (Ketje, ...

14

The origin is set theory and not programming languages. In the context of cryptography, I could describe a set that is $$x_1 \parallel x_2 \parallel \dots \parallel x_n$$ as a concatenation of the series described by $$\parallel_{i=1}^n x_i.$$ Furthermore, it's worth noting that + to a mathematician would suggest that it is a commutative, which might not ...

11

This closure is a rather stupid thing, because the Web site is not closed: indeed, there still is a machine, somewhere, which responds to HTTP requests and returns the "we are closed" page. It would have cost zero effort, and zero extra money, to simply let the Web site run and keep on serving PDF files. For crypto development, this means that until the US ...

11

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 ...

10

PSS is harder to implement because it uses randomness -- randomness is hard on many embedded systems like smart cards. The most proclaimed advantage of PSS is that it has a "security proof" with, apparently, a rather tight reduction (see this page for some references). Security proofs are not an easy subject; the proof for OAEP (the encryption padding which ...

10

It's merely an update to align the hashing algorithms. There are in fact no real "consequences" which might have any negative impact as the v2.1 schemes are still supported. The positive impact is the alignment with FIPS 180-4. To quote the revision history at page 59 of "PKCS #1 v2.2: RSA Cryptography Standard": Version 2.2 updates the list of allowed ...

10

Multi-prime RSA (also known as RSA-MP) is supported by PKCS#1v2. This standard supports a public key $(n,e)$ where the modulus $n$ is the product of $u≥2$ distinct odd primes: $n=\prod_{i=1}^u{r_i}$, with $1<e<n$ and $\gcd(r_i-1,e)=1$ (implying $e$ odd). The private exponent $d$ is such that $1<d<n$, and $e⋅d≡1\pmod{\operatorname{lcm}_{i=1}^u(r_i-... 10 Please bear in mind that this information is all secondhand. I have not looked closely at the original drafts of Hash DRBG (although you might find a draft that's early enough if you peruse the FOIA results in [1]). However, during conversations with folks at NIST I was told that there were certain weaknesses in early drafts of Hash DRBG that were very ... 10 I don't have any visibility into the BSI standardization process, and so this is a guess; I suspect one of two things happened: This is a potential way to deal with someone figuring out how to break both Brainpool and NIST curves (but not arbitrary elliptic curves; if they managed that, this hook won't help). In that case, if someone did that (or if we ... 9 Some languages like PL/I and Oracle Database SQL indeed use || for string concatenation. One reason is maybe that + might be confusing when talking about fundamental cryptography, since there is a lot of math involved. The mathematical notation for 'OR' would be reversed caret$\lor$and the exclusive 'OR', better known as 'XOR' is a circled plus$\oplus$. ... 8 Bernstein and Lange says that there has been no progress for prime-field elliptic curves since about 1999, when the NIST curves were chosen. No large class of weak curves were known then, and no large class is known now. Some small classes are known, (as Neves says) the curves with small embedding degree and the anomalous curves (order$n$equals the prime$...

8

If you are seeking a government contract with China, you might be required to use Chinese government standards for cryptography, just like if you are seeking a government contract with the United States, you might be required to use United States government standards for cryptography. There are many national pride cryptography standards that have little ...

7

This is all about the question of risk assessment. Are you willing to risk all devices together so that if one key is compromised, they all have to be returned? What is the cost of one return, 100 returns, or 100,000 returns? What is the expense of issuing a master key? Of issuing ten master keys? Of issuing a thousand? Do you have an estimate for how ...

7

Under the assumption that $(K,\text{Msg})\to H_K(\text{Msg})$ is a secure MAC (be it HMAC or any other MAC), and $\text{Nonce}$ does not repeat and is of fixed size, both $H_K(\text{Msg}||\text{Nonce})$ and $H_K(\text{Nonce}||\text{Msg})$ are demonstrably secure, in the sense that an adversary not knowing $K$ can't distinguish either from random, even for ...

7

The PKCS#11 standard has transitioned from RSA to the OASIS group: https://www.oasis-open.org/committees/tc_home.php?wg_abbrev=pkcs11 I am not sure why RSA/EMC's site doesn't mention this. I believe that v2.30 was close to finalization, but was never formally released. I am not sure what happened but v2.40 is now the current release candidate. v2.20 is ...

7

I ("SEJPM" as of now) have contacted the authors asked them the same questions as in my question. I'm posting this as community wiki, as it's not my answer to this question but rather theirs. Now the responses follow: First off, the authors are working on a design rationale in english for their new cipher. As soon as it's published, it will be linked here. ...

7

To clarify scope: FIPS 140-2 itself doesn't say anything about DSS, though it has 186-2 as a reference. It was published in 2001, before 186-3 and -4, and has not been superseded. After 140-3 spent 8 years in draft they recently decided to consider using ISO/IEC 19790 instead! 140-2 Annex A (Approved functions) is updated frequently and does now reference ...

7

Much of what NIST publishes about cryptographic algorithms is in Special Publications. In this case it is SP 800-131 (pdf) where they describe transitioning away from old algorithms and key sizes. Pages 14-15 have the hash function specific information: SHA-1 for digital signature generation:      SHA-1 may only be used for ...

7

Political reasons likely wins. E.g. France has an own set of domain parameters. Note that when the spec was created that the Brainpool curves where rather new. Generating safe parameters is not trivial, but we're talking countries here. Most of them will simply copy what's out there or buy a solution, but a few of the more advanced ones can try other curves ...

6

I don't know, but block-cipher based modes of operation have seen a lot more scrutiny. AES in CTR mode has been vetted much more thoroughly than any of those stream ciphers you mention. Moreover, those stream ciphers do not offer compelling benefits over AES-CTR mode. Therefore, it seems to me it would be entirely reasonable to focus on block-cipher based ...

6

The cornerstone of the handshake security is that the Finished messages, sent under the protection of the newly exchanged key (for encryption and MAC), contain hash values computed over all the handshake messages exchanged so far, including the list of cipher suites and all other parameters. As long as client and server don't negotiate the use of a cipher ...

6

As far as I can tell, NIST has only one official document about entropy collection. SP-800-90B. The purpose of NIST Special Publication (SP) 800-90B is to specify the design and testing requirements for entropy sources that can be validated as approved entropy sources by NIST‘s CAVP and CMVP. It essentially defines a bunch of statistical tests to ...

6

First up: Don't believe the hype! Especially if things can easily be proven wrong. What I mean is that your NIST have just launched a new service… is incorrect, as the NIST Randomness Beacon project is known to me (and others) since 2011. Furthermore, this project was awarded a multi-year grant from NIST's Innovations in Measurement Science (IMS) Program in ...

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