Why encrypted backup is so important
You might have seen the news today that Apple is announcing a raft of improvements to Macs and iOS devices aimed at improving security and privacy. These include FIDO support, improvements to iMessage...
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Remarks on “Chat Control”
On March 23 I was invited to participate in a panel discussion at the European Internet Services Providers Association (EuroISPA). The focus of this discussion was on recent legislative proposals,...
View ArticleBook Review: Red Team Blues
As a rule, book reviews are not a thing I usually do. So when I received an out-of-the-blue email from Cory Doctorow last week asking if I would review his latest book, Red Team Blues, it took a...
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PRFs, PRPs and other fantastic things
A few weeks ago I ran into a conversation on Twitter about the weaknesses of applied cryptography textbooks, and how they tend to spend way too much time lecturing people about Feistel networks and...
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On Ashton Kutcher and Secure Multi-Party Computation
Back in March I was fortunate to spend several days visiting Brussels, where I had a chance to attend a panel on “chat control“: the new content scanning regime being considered by the EU Commission....
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Some rough impressions of Worldcoin
Recently a reader wrote in and asked if I would look at Sam Altman’s Worldcoin, presumably to give thoughts on it from a privacy perspective. This was honestly the last thing I wanted to do, since...
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To Schnorr and beyond (Part 1)
Warning: extremely wonky cryptography post. Also, possibly stupid and bound for nowhere. One of the hardest problems in applied cryptography (and perhaps all of computer science!) is explaining why...
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To Schnorr and beyond (part 2)
This post continues a long, wonky discussion of Schnorr signature schemes and the Dilithium post-quantum signature. You may want to start with Part 1. In the previous post I discussed the intuition...
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Attack of the week: Airdrop tracing
It’s been a while since I wrote an “attack of the week” post, and the fault for this is entirely mine. I’ve been much too busy writing boring posts about Schnorr signatures! But this week’s news...
View ArticleA quick post on Chen’s algorithm
Update (April 19): Yilei Chen announced the discovery of a bug in the algorithm, which he does not know how to fix. This was independently discovered by Hongxun Wu and Thomas Vidick. At present, the...
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Is Telegram really an encrypted messaging app?
This blog is reserved for more serious things, and ordinarily I wouldn’t spend time on questions like the above. But much as I’d like to spend my time writing about exciting topics, sometimes the...
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Let’s talk about AI and end-to-end encryption
Recently I came across a fantastic new paper by a group of NYU and Cornell researchers entitled “How to think about end-to-end encryption and AI.” I’m extremely grateful to see this paper, because...
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How to prove false statements? (Part 1)
Trigger warning: incredibly wonky theoretical cryptography post (written by a non-theorist)! Also, this will be in two parts. I plan to be back with some more thoughts on practical stuff, like cloud...
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How to prove false statements? (Part 2)
This is the second part of a two three-part series, which covers some recent results on “verifiable computation” and possible pitfalls that could occur there. This post won’t make much sense on its...
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U.K. asks to backdoor iCloud Backup encryption
I’m supposed to be finishing a wonky series on proof systems (here and here) and I promise I will do that this week. In the midst of this I’ve been a bit distracted by world events. Last week the...
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How to prove false statements? (Part 3)
This is the third and penultimate post in a series about theoretical weaknesses in Fiat-Shamir as applied to proof systems. The first post is here, the second post is here, and you should probably...
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Three questions about Apple, encryption, and the U.K.
Two weeks ago, the Washington Post reported that the U.K. government had issued a secret order to Apple demanding that the company include a “backdoor” into the company’s end-to-end encrypted iCloud...
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Dear Apple: add “Disappearing Messages” to iMessage right now
This is a cryptography blog and I always feel the need to apologize for any post that isn’t “straight cryptography.” I’m actually getting a little tired of apologizing for it (though if you want some...
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A bit more on Twitter/X’s new encrypted messaging
Update 6/10: Based on a short conversation with an engineering lead at X, some of the devices used at X are claimed to be using HSMs. See more further below. Matthew Garrett has a nice post about...
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Kerberoasting
I learn about cryptographic vulnerabilities all the time, and they generally fill me with some combination of jealousy (“oh, why didn’t I think of that”) or else they impress me with the brilliance of...
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