Comment by KirillPanov | Hacker News Reader

Comment by KirillPanov | Hacker News Reader

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I feel like packet size was and continues to be a major obstacle for DNSSEC. Do you know why the DNSSEC/DANE world hasn't simply acknowledged this and switched to requiring ECC?

It is trivial to fit several compressed curve points (i.e. signatures) in a single packet, whereas you can't even fit two RSA signatures in a minimum-safe-to-assume DNS UDP reply packet after accounting for padding and ASN.1 overhead.

I get the feeling that there is some faction that really hates UDP and they sort of hijacked the DNSSEC situation to use as a lever to force people to allow DNS-over-TCP.

That seems to be backfiring, however, and DNSSEC has wound up taking a bullet for the UDP-haters.

Many very-large networks simply can't afford for their DNS traffic to be exposed to TCP's intrusion-detection malleability and slowloris (resource exhaustion) attacks. These networks appear to be simply ignoring the "thou must TCP thine DNS" edict. DNSSEC is not a good enough carrot for them. I think ditching RSA would have been a more pragmatic choice than ditching UDP or skipping DNSSEC.

Dunno why there are so many foot-draggers failing to deploy better DNSSEC algorithms. I’m grumpy about SHA-1 in particular https://datatracker.ietf.org/doc/html/draft-fanf-dnsop-sha-l...

When I query vjhv.verisign.com I get a response containing four 2048 bit RSA-SHA-2 signatures in 1049 bytes which is well within the EDNS MTU for unfragmented UDP, so I’m not convinced the problem is as bad as you paint it. There have been problems with EDNS trying to use fragmented UDP, but that has been reduced a lot by newer software being more cautious about message size limits for DNS over UDP.

DNS needs TCP even in the absence of DNSSEC, because there are queries you cannot resolve without it. Some operators might convince themselves they can get away without it, but they will probably suffer subtle breakage.

> four 2048 bit RSA-SHA-2 signatures in 1049 bytes which is well within the EDNS MTU for unfragmented UDP

I was referring to the non-EDNS 512-byte limit.

Yes, you get ~2.5 times more with EDNS. Still, four records is not a lot.

> DNS needs TCP even in the absence of DNSSEC, because there are queries you cannot resolve without it.

Theoretically? Perhaps. Some would argue that connectionless DNS is valuable enough that people should not create those resource records. Before DNSSEC that was a working consensus. And with ECC it could be once again.

That's the opposite of the direction Internet cryptography is going, given hybrid PQC and classical systems.

The bloaty key/signature size is only a problem with the PQ encryption systems.

For signing only there are much more efficient PQ cryptosystems, with signatures around the same size as ECC. If DNSSEC ever adopts PQC it will be one of those systems.

Here are two of the earliest, and easiest to understand. There are much better ones now.

https://en.wikipedia.org/wiki/Lamport_signature#Short_keys_a...

https://en.wikipedia.org/wiki/Merkle_signature_scheme

Mostly, it's because very few serious engineering organizations deploy DNSSEC at all, so the best practices and tooling support aren't there.

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