91 points by nabla9 1 day ago | 37 comments
tptacek 1 day ago
On the chopping block:
* ECB (\o/)
* Triple DES (TDEA)
* Finite field DSA (for new signatures)
* ECDSA at strengths lower than 112 bits
* RSA below 2048 bits
* RNGs, HMACs, HKDF, PBKDF and hashes based on SHA1 and the truncated 224-bit SHA-2/3 modes
No big surprises. The 224's are interesting, because folklorically they have value in hash constructions where resistance to length extension is useful. In practice, everyone just uses HMAC anyways.
*
deknos 1 day ago
regarding finally transitioning away from SHA1: about fucking time :D
adrian_b 20 hours ago
For instance the CTR mode can be used to encrypt any number of bits, down to a single bit.
The problem of the other modes vs. ECB is that they require the generation and the transmission of an "intialization vector", i.e. either a counter value or a random number, depending on the mode, so besides the short encrypted data a longer whole block must be transmitted. This can be avoided only when a set of small data are considered as parts of a long sequence of encrypted data, so the encryption mode is not reinitialized at each new message, but the last state is remembered.
ECB is a valid encryption mode only when it is used to encrypt random numbers having the length of the block (or other kind of data for which there is a strong guarantee that there will be no repeated values). It is secure for challenge-response authentication, if the challenges are unpredictable random numbers. ECB would be a perfectly secure method for encrypting other encryption keys, which must be random, except that one might want to encrypt together with the values of the keys other data, such as identifiers or error detection codes, in which case ECB could not be used to encrypt the additional non-random data.
tptacek 1 day ago
js2 1 day ago
PeterWhittaker 15 hours ago
AIUI, symmetric algorithms such as 3DES are not subject to these attacks, but my understanding could be wrong.
Care to enlighten?
tptacek 14 hours ago
PeterWhittaker 13 hours ago
sidewndr46 1 day ago
adrian_b 20 hours ago
Only amateurs would choose to implement a "Triple AES", so it is very likely that they will also write a buggy implementation. Triple DES has not been used because it was a good strengthening method, but only because it could be used with unmodified hardware modules designed for simple DES. When a cipher strengthening is done in software, there are much better methods.
The best way to strengthen AES above the standard AES-256 is to double the block length from 128 bits to 256 bits. Increasing the key length over 256 bits is much less useful, because the key length is not the weakest point of AES-256. A 256-bit key is strong enough even against quantum computers, but short 128-bit blocks can be a vulnerability in certain applications. The key schedule algorithm of AES, which converts the cipher key into a set of round keys, is mediocre, so the length of the cipher key is the least important concern about the strength of AES.
The original Rijndael proposal had a stronger variant with 256-bit blocks, which has not been retained in the standard. Nevertheless, it is easy to implement it with the Intel/AMD AES instructions or with the Arm Aarch64 AES instructions. Intel has even published an application note describing how to do this, when the AES instructions have been introduced in the Westmere CPUs.
After increasing the block length, increasing the number of rounds can provide additional strengthening. Another choice would be to replace the standard key schedule algorithm with a stronger non-standard algorithm (i.e. one providing more random round keys). Increasing the key over 256 bits provides a much less useful strengthening in comparison with the cost required for executing the additional necessary operations.
sidewndr46 14 hours ago
Joel_Mckay 1 day ago
SPHINCS+ / FIPS 205 should be available soon.
FALCON ...unknown FIPS draft TBA soon.
These are newer quantum resistant algorithms, and should be considered in your future maintenance cycle as they become available in the libraries.
NIST has some of the brightest minds in the world. When they suggest something, than one should probably take the advice very seriously. =3
tptacek 1 day ago
cperciva 1 day ago
dfc 1 day ago
cperciva 1 day ago
Joel_Mckay 1 day ago
deknos 1 day ago
Joel_Mckay 1 day ago
gnupg 2.4.3
libassuan 2.5.6
libgcrypt 1.10.3
libgpgerror 1.47
libksba 1.6.5
npth 1.6
pinentry 1.2.1
However, the Kyber algorithm was only committed recently in libgcrypt 1.11.0, and will not build on some platforms due to an libassuan 3.0.1 issue.
Did you have additional details on when a working packaged set of dependencies will be available for static .a builds that support Kyber?
Have a great day =3
upofadown 1 day ago
* https://articles.59.ca/doku.php?id=em:20482030
The document specifies that SHA-1 in HMACs is the be entirely disallowed after 2030. That seems like it would cause needless reimplementation of systems with the associated chance of security problems and expense. SHA-1 used in an HMAC is generally known to be secure.
tptacek 1 day ago
The 2048 deprecation in 2030 seems to be about quantum resistance, not about a move to 4096 bit RSA.
LegionMammal978 1 day ago
From [0], where the 112-bit 'security strength' of 2048-bit RSA is ultimately pulled from:
"The comparable security strengths provided below are based on accepted estimates as of the publication of this Recommendation using currently known methods. Advances in factoring algorithms, general discrete-logarithm attacks, elliptic-curve discrete-logarithm attacks, and other algorithmic advances as well as quantum computing may affect these equivalencies in the future. New or improved attacks or technologies may be developed that leave some of the current algorithms completely insecure."
Their recommendation is to switch to 3072-bit RSA or higher by 2031, since that has a 128-bit 'security strength' by their formula. So I don't think this has much to do with quantum resistance: as GP says, no reasonable RSA key size will help much with that.
[0] https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.S..., section 5.6.1
tptacek 1 day ago
upofadown 18 hours ago
>Currently, a 112-bit security strength for the classical digital signature and key-establishment algorithms does not appear to be in imminent danger of becoming insecure in the near future, so this approach should allow an orderly transition to quantum-resistant algorithms without unnecessary effort for the cryptographic community.
I get from this that NIST thinks the quantum threat is significantly greater than the threat from advances in classical computing hardware or algorithms. So we are to not to bother with transitioning from 112 bit to 128 bit equivalent strength and to concentrate on post quantum stuff. As a result stuff like 2048 bit RSA is now allowed at the "deprecated" level where it was previously "disallowed" after 2030.
It seems that both the quantum and classical threats both currently depend on a fundamental breakthrough so I am not sure how legitimate this policy is. It is reminiscent of the NSA suggestion to not bother transitioning to elliptic curve based methods and skip directly to post quantum methods.
tptacek 14 hours ago
Credible new systems aren't going to be developed with RSA, regardless.
deknos 1 day ago
veggieWHITES 1 day ago
[1] https://en.wikipedia.org/wiki/National_Institute_of_Standard...
gruez 1 day ago
y-curious 1 day ago
archgoon 1 day ago
kurikuri 3 hours ago
User23 18 hours ago