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Comment by mswphd

4 days ago

this is literally what happened with previous NSA meddling though? Both DUAL_EC_DRBG and DES were done "officially" by the NSA.

Additionally, the main authors behind ML-KEM are all european. The design of ML-KEM is "very boring", in the sense that it's essentially the scheme that most (lattice) cryptographers would have suggested. There were 2 other NIST PQC schemes that went very far (New Hope and Saber) that were essentially the same scheme (there were minor technical differences, but it's really not that big).

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mswphd

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adrian_b  4 days ago

DJB did not criticize anything about ML-KEM.

The TFA has nothing to do with ML-KEM, but only about how to transition from the current algorithms to post-quantum algorithms.

For now, it is completely unknown how secure ML-KEM really is, because it is too new. For many complex cryptographic algorithms a decade or even a few decades have been required until someone discovered how to break them. The predecessor of ML-KEM, SIKE, has already been broken. Perhaps nobody will break ML-KEM, or perhaps it will be broken in a couple of years.

The only risk-free strategy is to use both ML-KEM and the current key exchange algorithm. This adds a negligible cost, because ML-KEM is much more expensive.

Therefore I agree with DJB about this, because I never bet that the worst case will not happen. Any good design must work fine even when the worst happens.

  • mswphd  4 days ago

    DJB wrote this article after asking people to brigadge the current TLS-WG's attempt to get rough consensus on a current draft RFC for pure ML-KEM. This is clearly part of this tirade for that.

    ML-KEM is not new. It's hardness is based on MLWE. LWE (a slightly harder problem) has been around for 20 years. Attacks against it stablized to be 2^{cn} time maybe 15 years ago. The value of c has been stable for nearly 10 years.

    MLWE is mildly different, but still from > 1 decade ago. The only improved attacks are ~8x faster (and they are relatively naive). It has been a very popular cryptanalytic target since it was suggested (LWE has been dominating cryptography for the last >10 years).

    It does not add negligible cost in all settings. In hardware, a hybrid scheme requires an implementation of SHA2 and SHA3. This is expensive.

    Any good design must not do fine when even the worst happens. When we did the AES competition, we did not combine AES with DES (or 3DES) in case AES was weak.

    This is beside the point though. Most cryptographers would still recommend the hybrid over pure ML-KEM. This RFC (for pure MLKEM) is marked "recommended to implement = N". It is purely for settings where the implementors independently want to use pure ML-KEM for some reason. In these settings, they should implement it against some standard, so it is interoperable.

    • tveita  4 days ago

      > Most cryptographers would still recommend the hybrid over pure ML-KEM. This RFC (for pure MLKEM) is marked "recommended to implement = N". It is purely for settings where the implementors independently want to use pure ML-KEM for some reason.

      That's exactly how it was with Dual_EC_DRBG.

      E.g. https://www.schneier.com/essays/archives/2007/11/did_nsa_put...

         I don’t understand why the NSA was so insistent about including Dual_EC_DRBG in the standard. It makes no sense as a trap door: It’s public, and rather obvious. It makes no sense from an engineering perspective: It’s too slow for anyone to willingly use it. And it makes no sense from a backwards-compatibility perspective: Swapping one random-number generator for another is easy.
  
  My recommendation, if you’re in need of a random-number generator, is not to use Dual_EC_DRBG under any circumstances.

      So most cryptographers _recommended_ staying the hell away from Dual_EC_DRBG. But hey, harmless, no one serious about security would actually use it right?

      Except as we know now, after the standardization NSA was able to persuade/bribe vendors to implement it.

      RSA is still a viable cryptography vendor, after accepting money to backdoor their product for paying customers. The standardization gave them a fig leaf of plausible deniability. Honest mistake, could happen to anyone, right? If they had needed to implement a "non-standard" backdoor, or if it had been officially struck from the standard, it would have been a lot harder to row away from.

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iAMkenough  4 days ago

2006's NSA is not 2026's NSA

  • some_furry  4 days ago

    The NSA isn't DJB's oppositiom here. It's the majority of the international community of cryptography experts.

    • adrian_b  4 days ago

      Your claim does not match the reality, because at the previous IETF meeting most have voted like DJB.

      I cannot see how any true "expert" would have the courage to claim that in a cryptography standard it is admissible to accept risks that cannot be quantified.

      For the variant supported by DJB there are no risks, while for the variant supported by NSA nobody can estimate the risks.

      It is as simple as this, so it is weird that there are people arguing about a decision that should have been non-controversial.

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