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Aleksei Udovenko

@affine.group

Researcher in Cryptography (symmetric-key, white-box, post-quantum, etc.) https://affine.group

18 Posts140 Follower73 Folgt
Maria Corte-Real Santos@maria.isogeny.club · yesterday

New paper dropped! We explore the expansion properties of the superspecial isogeny graph in dimension g > 1 (with level structure), and give several applications of this result. tl;dr: they are not optimal expander graphs but still provide enough expansion for cryptographic use! ia.cr/2026/2429

Rapid mixing in superspecial isogeny graphs

We prove expansion properties of superspecial isogeny graphs in dimension $g \geq 2$, including arbitrary level structure. In particular, we provide explicit bounds for the spectral gap, and a fine ch...

ia.cr

Krijn Reijnders @krijn.isogeni.es · 2w ago

New paper! Given a Jacobian over Fp, can you easily check supersingularity? If you've worked with these objects in magma, you know how annoying this question can be. Turns out it's very easy: we give efficient probabilistic tests, and conclusive if you need to be absolutely sure. ia.cr/2026/2259

Supersingularity and Superspeciality Verification of Abelian Surfaces

Supersingular abelian surfaces are essential in isogeny-based cryptography. Despite this, we have no efficient algorithm to verify if a given abelian surface is supersingular. In this work, we initiat...

eprint.iacr.org

No One Upstairs@nooneupstairs.bsky.social · 2w ago

Yes, to all the thread. But government assessment of universities would need to change away from for-profit, quantity & IF. Many times, the rules for assessment are made by academics who enjoy the status quo, and so we continue with these problems.

Mark A. Hanson@hansonmark.bsky.social · 3w ago

There is one regulatory mechanism that can make this happen: funder and university action. Funders and universities require the research they fund to be published. Great, keep doing that. Just require it to be in non-profit journals. Keep walking and talking with me here... 👣 9/n

Total Internal Reflection🇬🇧🇺🇸🇺🇦@tirscienceblog.bsky.social · 3w ago

Great 🧵 from @hansonmark.bsky.social on why all academics should be opting to publish in non-profit journals 👏👏👏👇

Mark A. Hanson@hansonmark.bsky.social · 3w ago

I'm surprised a community of publishing writers can blame AI for the problems of peer review when those same writers cite our study, "the strain on scientific publishing", which characterizes how this problem existed before AI. bit.ly/StrainQSS It's the incentives structure, not the AI. 1/n

John Stott@jpsastro.bsky.social · 3w ago

Had a UKRI funded grant proposal rejected at the "AI triage stage". "This AI-based triage was used only to identify approximately 50% of the strongest proposals to take forward to full human review." 🧪 #academicsky

I am writing to let you know that, unfortunately, your application was not successful. Review process As part of the initial triage of the 179 proposals submitted to this call, each was assessed using an AI-based review. Every proposal was read independently by several different AI models against the same seven criteria used to shape this call (including cyber security relevance, research quality and novelty, importance of the problem addressed, feasibility of the project plan, likely outputs and impact, value for money, and responsible research practice), with each model asked to give a score and a written justification with supporting quotations from the text. To guard against any one model's idiosyncrasies, we also ran a second, independent process in which different AI models debated the merits and weaknesses of each proposal before reaching a judgement, again against the same criteria. Scores from both processes were combined to produce an overall ranking. This AI-based triage was used only to identify approximately 50% of the strongest proposals to take forward to full human review. Projects selected for funding were drawn from those that progressed to the full human review stage. We recognise that AI-assisted assessment is a new and evolving part of the review process, and we are continuing to evaluate how well it aligns with the judgements of human reviewers on this call. We will soon produce a document detailing our method, so that others can build upon it and improve it. Feedback on your application Your application was not selected to progress beyond the AI triage stage. To provide transparency on the outcome of this assessment, we are sharing below the scores (out of 5) from each of the two AI review processes described above, together with the mean score across the two processes.
Clément Canonne@ccanonne.github.io · 3w ago

Quite the exciting talk by Ryan O'Donnell (@booleananalysis.bsky.social) at the Simons Institute next week, on Expander Graphs. We'll finally know which ones are his favorites! Livestream option available upon (free) registration: simons.berkeley.edu/events/my-fa... @simonsinstitute.bsky.social

My Favorite Expanders | Richard M. Karp Distinguished Lecture

Expander graphs are sparse graphs for which, whenever you split the graph into two parts, the number of edges going between the parts is proportional to the size of the smaller part. There are extreme...

simons.berkeley.edu

Helger Lipmaa@helger.bsky.social · 4w ago

A different view. As a cryptographer (or maybe, as me - some cryptographers are in a different camp), I mostly agree with what @wtgowers.bsky.social is saying - my goal is to solve problems, and if AI does it better, then so be it. My problem is ethical. The way (say) OpenAI approaches it is wrong.

Timothy Gowers@wtgowers.bsky.social · 4w ago

I've written a blog post responding to the letter about maths and AI signed by 25 Fields medallists. As with the Leiden Declaration, I didn't sign it, but I agree with much of it and welcome its existence. gowers.wordpress.com/2026/09/17/w...

Kenny Paterson@kennyog.bsky.social · last mo.

TL;DR: using compression before encryption is much weaker than we thought. Tiny length differences can be amplified - almost without limit - and noise-based or bucketization countermeasures are then easy to bypass. Joint work with @prefix-free.bsky.social and Lenka Mareková, to appear at CCS 2026.

ePrint Updates@eprint.ing.bot · last mo.

Criminology: Refined Techniques for Compression Side-Channel Attacks (Yuanming Song, Lenka Mareková, Kenneth G. Paterson) ia.cr/2026/1972

Abstract. It has been known for two decades that performing compression before encryption is dangerous, because it introduces a side channel leaking information about plaintexts through ciphertext lengths: the compressed plaintext length may be visible in the ciphertext length, and the amount of compression obtained is plaintext-dependent; hence an adversary can obtain some leakage about the plaintext via observation of ciphertext lengths. This issue was first pointed out by Kelsey (FSE 2002) and turned into a practical plaintext recovery attack in the form of the CRIME attack on SSL and TLS by Rizzo and Duong in 2012. A long series of variations and attacks against other systems followed. Despite the known dangers, the compress-then-encrypt paradigm is still prevalent in practice today. This may be because the compression-based side channel is susceptible to noise and may require a large number of queries to enable plaintext recovery, and so can be mitigated by either adding noise (e.g. with random padding) or limiting an adversary’s interaction with the system. We demonstrate that this side channel is much more powerful than previously thought. We focus on the widely-used DEFLATE algorithm in our analysis. We present novel techniques that enable strong amplification of small length differences arising during compression. Our telescoping and chaining amplification techniques exploit the way in which DEFLATE replaces common strings by shorter back-references. Our collision-based amplification technique focusses on exploiting hash table collisions in DEFLATE implementations. This involves a deeper examination (and exploitation) of the internals of DEFLATE than in previous works. These insights result in compressed length differences growing linearly with the length of queries. Compared with length differences of a few bits or bytes in prior work, our new amplification techniques thus enable us to defeat existing noise-based countermeasures. Finally, we introduce the concept of CRIME automata, these being carefully crafted query strings that enable an attacker to exert fine control over the internal behaviour of DEFLATE and produce differences in the output lengths of the compressor according to various criteria (such as whether the DEFLATE sliding window contains a given target string). In turn, our automata are composed in a modular fashion from gadgets having different functions, including matching against target strings, performing logical operations between other gadgets, and, most importantly, amplifying differences in output lengths using the above-mentioned techniques. We provide multiple, concrete automata designs that serve different attack goals. These designs are supported by experiments and a publicly available codebase demonstrating the power, flexibility, and practical impact of our CRIME automata approach.
Eric Schares@eschares.bsky.social · last mo.

🚨Update: Our analysis of global APC expenditure has now been expanded to cover more publishers (7 -> 14) and more years (2019-2025). We estimate $15B in APCs paid over seven years, $3.7B in 2025 alone. Elsevier crosses the $1B threshold by itself in 2025. arxiv.org/abs/2608.16322 #ScholComm

Line chart showing 5 biggest publishers from 2019-2025
Eric Schares@eschares.bsky.social · 2y ago

🚨 Preprint! We combine our recent open dataset of #APC prices with the article counts per journal-year from #OpenAlex to estimate how much the academic community has paid in APCs over the last 5 years. A. $8.349 billion ($8.968 B in 2023 USD) $2.5B in 2023 alone. arxiv.org/abs/2407.16551 #metasci

Jess Miers 🦝@jmiers230.bsky.social · last mo.

I did a somewhat deep dive into the recent OpenAI and Anthropic "hacks" for an upcoming interview. IMO, the AI companies are better off running with the "rogue AI" story because the real story is actually pretty embarrassing. Like making your Wi-Fi password "wifi" embarrassing. 🧵