Huck Bennett

Huck Bennett

@huckbennett.bsky.social

Faculty at the University of Colorado. Interested in theoretical computer science, and especially lattices. Also: mountains, running, music. https://home.cs.colorado.edu/~hbennett/

726 followers236 following193 posts

Holy crap! I find this way, WAY more surprising than the 3-SUM and APSP results, which I already found extremely surprising. "Just" SETH would have already been gigantic if somewhat less surprising. A few comments:

Ryan Williams@rrwilliams.bsky.social

An internal model at OpenAI has produced a claimed refutation of ETH! Russell Impagliazzo, Mohan Paturi, and I have been asked to help organize an open and independent examination of this claim. 1/4

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Holy crap! I find this way, WAY more surprising than the 3-SUM and APSP results, which I already found extremely surprising. "Just" SETH would have already been gigantic if somewhat less surprising. A few comments:

Ryan Williams@rrwilliams.bsky.social

An internal model at OpenAI has produced a claimed refutation of ETH! Russell Impagliazzo, Mohan Paturi, and I have been asked to help organize an open and independent examination of this claim. 1/4

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To be clear, I'm not downplaying the magnitude of this result, which is insane. But, it's still interesting that they shave logs in the exponent instead of getting, say, a 2^{O(sqrt(n))}-time algorithm. It'd be ridiculous if this were the "right" running time for k-SAT.

Holy crap! I find this way, WAY more surprising than the 3-SUM and APSP results, which I already found extremely surprising. "Just" SETH would have already been gigantic if somewhat less surprising. A few comments:

Ryan Williams@rrwilliams.bsky.social

An internal model at OpenAI has produced a claimed refutation of ETH! Russell Impagliazzo, Mohan Paturi, and I have been asked to help organize an open and independent examination of this claim. 1/4

1. The recent string of algorithmic AI results have really changed my priors about what's hard. I would have guessed that our algorithms for any of int. mult., FFT, Subset Sum, 3-SUM, APSP, and k-SAT are close to optimal, although not all with the same level of confidence.

The timing of this is very funny to me too. I'm teaching both undergrad and grad algorithms this semester, and, as I have done many times before, I offer an automatic A in the class to anyone who improves on certain algorithms that we see. Of course, I don't give out automatic As so easily...

My undergrad lecture tomorrow is mostly about APSP/Floyd-Warshall, and since I'm a super generous guy, I planned to give an automatic A to anyone who found a O(n^{3-eps})-time algorithm for APSP. The kicker: this is the third time an "automatic A" problem I've given has been solved this semester!

Is reading and understanding a paper the same as writing a paper? What about rewriting a paper in my own words? Now, what if I pay my (hypothetical) human friend Eliza $200 a month to write papers for me with the understanding that I'll put my name on them but add in an Eliza statement? 2/2

Incompetence and/or malpractice. As with any powerful and dangerous tool, "Whoops! How did that happen? We didn't expect that." is not acceptable. (The OpenAI equivocating that Jeremy got on Twitter is not at all convincing.)

Jeremy Kun@jeremykun.com

Why doesn't OpenAI simply air-gap the machines and networks it runs these "dangerous" AI experiments on?

Wow does the post title bury the lede! I particularly like the pictured comment.

Nalini Joshi@monsoon0.bsky.social

Initial Members of the Advisory Group on Mathematics and AI⁠: Camillo De Lellis (IAS) Timothy Gowers (Cambridge) Martin Hairer (EPFL) Nikhil Srivastava (Berkeley) Ulrike Tillmann (Oxford) Ravi Vakil (Stanford) Edward Witten (IAS) Melanie Matchett Wood (Harvard) terrytao.wordpress.com/2026/09/21/a...

Congratulations to PNW running/mountain friend Jess (and her esteemed pacer Colin) on outright winning the Mountain Lakes 100-mile race in Oregon! She was 50 minutes ahead of #2 (also a woman) and ~78 ahead of the first man. Fun fact: 100% of my volcano summits have been with Colin and Jess!

💯. What a sad place we've ended up in. A year or two ago, we'd just be celebrating the results and the authors.

Nutan Limaye@nutanlimaye.bsky.social

This is not where I expected TCS to be in 2026! The last line in the abstract is distressing. :( Is this how we need to work when we get a big result? As if someone is always chasing us?

I'm in Ottawa, ON, Canada to give a couple of talks at the Selected Areas in Cryptography (SAC) summer school on Monday: sacworkshop.org/SAC26/schedu.... The first is about lattice basics, LWE, and LWE optimizations. The second is on the lattice-isomorphism problem and related cryptography.

sacworkshop.orgSchedule - Selected Areas in Cryptography (SAC) 2026August 24–28, 2026 at the University of Ottawa. SAC is Canada's research conference on cryptography, held annually since 1994.

Here's a thread about four papers of mine that are being presented at conferences this week. I won't be at any of them due to the start of classes at CU, but my awesome students and collaborators will! (And, no, none of these papers used AI except for typo checking in one case.) 1/

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Here's a thread about four papers of mine that are being presented at conferences this week. I won't be at any of them due to the start of classes at CU, but my awesome students and collaborators will! (And, no, none of these papers used AI except for typo checking in one case.) 1/

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LCE is essentially the D = 1 case of code distortion. We give algorithms and show hardness, and study concepts like successive minima of codes and the 0 -> 0 "norm" on subspaces. This work adapts a number of ideas from analogous work on lattices (arxiv.org/abs/1605.03613). 12/

arxiv.orgOn the Lattice Distortion ProblemWe introduce and study the \emph{Lattice Distortion Problem} (LDP). LDP asks how "similar" two lattices are. I.e., what is the minimal distortion of a linear bijection between the two lattices? LDP ge...

Here's a thread about four papers of mine that are being presented at conferences this week. I won't be at any of them due to the start of classes at CU, but my awesome students and collaborators will! (And, no, none of these papers used AI except for typo checking in one case.) 1/

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Here's a thread about four papers of mine that are being presented at conferences this week. I won't be at any of them due to the start of classes at CU, but my awesome students and collaborators will! (And, no, none of these papers used AI except for typo checking in one case.) 1/

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As a bonus, in an appendix we give a careful write-up of a folklore very flexible/good compressed sensing scheme (works over any ring, has nearly optimal parameters and running time, measurement matrix is binary). See my previous comment on this too: bsky.app/profile/huck.... 7/

Huck Bennett@huckbennett.bsky.social

Congratulations to Venkat! We recently used the explicit expander construction from GUV (the CCC paper) to get a compressed sensing scheme, which is the key to our MM algorithms in arxiv.org/abs/2508.10250. (Thanks to @eigx.bsky.social for the pointer to GUV!)

Paper #3: "Hardness of the Binary Covering Radius Problem in Large ℓ_p Norms," arxiv.org/abs/2603.03219, at APPROX 26, with Peter Ly. The Covering Radius Problem (CRP) is one of the most fundamental lattice problems, but its complexity is not well understood compared to others. 8/

arxiv.orgHardness of the Binary Covering Radius Problem in Large $\ell_p$ NormsWe study the hardness of the $γ$-approximate decisional Covering Radius Problem on lattices in the $\ell_p$ norm ($γ$-$\text{GapCRP}_p$). Specifically, we prove that there is an explicit function $γ(p...

Here's a thread about four papers of mine that are being presented at conferences this week. I won't be at any of them due to the start of classes at CU, but my awesome students and collaborators will! (And, no, none of these papers used AI except for typo checking in one case.) 1/

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Paper #2: "Output-Sparse Matrix Multiplication Using Compressed Sensing," arxiv.org/abs/2508.10250, at RANDOM 26, with Karthik Gajulapalli, Alexander Golovnev, and Evelyn Warton. We give the fastest known deterministic algorithm for output-sparse MM (i.e., MM where the product matrix is sparse). 5/

arxiv.orgOutput-Sparse Matrix Multiplication Using Compressed SensingWe give two algorithms for output-sparse matrix multiplication (OSMM), the problem of multiplying two $n \times n$ matrices $A, B$ when their product $AB$ is promised to have at most $O(n^δ)$ many non...

We also match the fastest known randomized algorithms for OSMM (arxiv.org/abs/2309.06317). Our algorithms use a reduction to compressed sensing and in the randomized case, MM verification (so that a strong derandomization of Freivalds' algorithm would derandomize our OSMM alg). 6/

arxiv.orgThe Time Complexity of Fully Sparse Matrix MultiplicationWhat is the time complexity of matrix multiplication of sparse integer matrices with $m_{in}$ nonzeros in the input and $m_{out}$ nonzeros in the output? This paper provides improved upper bounds for ...

Here's a thread about four papers of mine that are being presented at conferences this week. I won't be at any of them due to the start of classes at CU, but my awesome students and collaborators will! (And, no, none of these papers used AI except for typo checking in one case.) 1/

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These primitives are Fully Homomorphic Encryption (computing on encrypted data) and Identity Based Encryption (PKE where a party's name or email address serves as the public key). The proofs port ideas from LWE crypto to LIP crypto. (The recent attack on HAWK does not affect this work.) 4/

Here's a thread about four papers of mine that are being presented at conferences this week. I won't be at any of them due to the start of classes at CU, but my awesome students and collaborators will! (And, no, none of these papers used AI except for typo checking in one case.) 1/

Huck Bennett reposted

Congratulations to Venkat! We recently used the explicit expander construction from GUV (the CCC paper) to get a compressed sensing scheme, which is the key to our MM algorithms in arxiv.org/abs/2508.10250. (Thanks to @eigx.bsky.social for the pointer to GUV!)

arxiv.orgOutput-Sparse Matrix Multiplication Using Compressed SensingWe give two algorithms for output-sparse matrix multiplication (OSMM), the problem of multiplying two $n \times n$ matrices $A, B$ when their product $AB$ is promised to have at most $O(n^δ)$ many non...

Simons Institute Director Venkat Guruswami has been honored this summer with STOC and CCC 2026 Test of Time Awards for papers that transformed coding theory and pseudorandomness, and emerged from a common algebraic core. simons.berkeley.edu/news/guruswa...

Yes, the result itself is very interesting (more on this below). From a skim, I agree with Noah that the paper is not well-written. Am I happy to see LLMs invade TCS? No, it's terrible. Is this the most impactful LLM result about lattices this week? Unclear. 1/

Clément Canonne@ccanonne.github.io

(same thing for @huckbennett.bsky.social and @noahsd.bsky.social , regarding the CVP one... If you have the time and energy of course!)

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Alas, not all approx factors γ are the same: γ-CVP for γ = n^{1/2} is in coNP, and so it likely isn't NP-hard. Still, the new result with γ = n^{1/200} comes close to the n^{1/2} barrier for the first time. Previously no poly hardness was known, and now it's a matter of pinning down the exponent. 4/

Oops: The paper shows hardness with γ = n^c in the ell_2 norm for c = 1/400, not c = 1/200. It gets c = 1/(200p) in the ell_p norm. As Chris pointed out, this is not at all tight though: bsky.app/profile/chri....

Chris Peikert@chrispeikert.bsky.social

2/ Strangely, Astra didn't optimize the polynomial approx factor! 1min with GPT-5.6 suggests that n^c -CVP is hard for **any c < 1/14** (not just c=1/400), simply by tightening up the bookkeeping. (Recall that c=1/2 is a fundamental barrier, where n^c-CVP is in NP \cap coNP.)

Yes, the result itself is very interesting (more on this below). From a skim, I agree with Noah that the paper is not well-written. Am I happy to see LLMs invade TCS? No, it's terrible. Is this the most impactful LLM result about lattices this week? Unclear. 1/

Clément Canonne@ccanonne.github.io

(same thing for @huckbennett.bsky.social and @noahsd.bsky.social , regarding the CVP one... If you have the time and energy of course!)

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Alas, not all approx factors γ are the same: γ-CVP for γ = n^{1/2} is in coNP, and so it likely isn't NP-hard. Still, the new result with γ = n^{1/200} comes close to the n^{1/2} barrier for the first time. Previously no poly hardness was known, and now it's a matter of pinning down the exponent. 4/

Was this the most important big-AI company LLM result about lattices this week? Theoretically, yes. Practically, no. Also, Claude found a faster exponential-time algorithm for a key recovery attack on the submitted-to-NIST signature scheme HAWK. See Chris's thread: bsky.app/profile/chri.... 5/5

Chris Peikert@chrispeikert.bsky.social

This is a very cool and exciting discovery by Claude Mythos! It found a serious 𝒎𝒂𝒕𝒉𝒆𝒎𝒂𝒕𝒊𝒄𝒂𝒍 attack on the post-quantum signature scheme HAWK, an "on-ramp" candidate for potential NIST standardization. www.anthropic.com/research/dis...

Yes, the result itself is very interesting (more on this below). From a skim, I agree with Noah that the paper is not well-written. Am I happy to see LLMs invade TCS? No, it's terrible. Is this the most impactful LLM result about lattices this week? Unclear. 1/

Clément Canonne@ccanonne.github.io

(same thing for @huckbennett.bsky.social and @noahsd.bsky.social , regarding the CVP one... If you have the time and energy of course!)

If you assume that γ-SVP and γ-CVP have similar complexity (which is often true) and treat all polynomial approx factors γ as about the same, this new result might suggest that we're close to basing (public-key) cryptography just on NP-hardness. That would be amazing. 3/