Ross Anderson unexpectedly passed away Thursday night in, I believe, his home in Cambridge.

I can’t remember when I first met Ross. Of course it was before 2008, when we created the Security and Human Behavior workshop. It was well before 2001, when we created the Workshop on Economics and Information Security. (Okay, he created both—I helped.) It was before 1998, when we wrote about the problems with key escrow systems. I was one of the people he brought to the Newton Institute, at Cambridge University, for the six-month cryptography residency program he ran (I mistakenly didn’t stay the whole time)—that was in 1996.

I know I was at the first Fast Software Encryption workshop in December 1993, another conference he created. There I presented the Blowfish encryption algorithm. Pulling an old first-edition of Applied Cryptography (the one with the blue cover) down from the shelf, I see his name in the acknowledgments. Which means that sometime in early 1993—probably at Eurocrypt in Lofthus, Norway—I, as an unpublished book author who had only written a couple of crypto articles for Dr. Dobb’s Journal, asked him to read and comment on my book manuscript. And he said yes. Which means I mailed him a paper copy. And he read it. And mailed his handwritten comments back to me. In an envelope with stamps. Because that’s how we did it back then.

I have known Ross for over thirty years, as both a colleague and a friend. He was enthusiastic, brilliant, opinionated, articulate, curmudgeonly, and kind. Pick up any of his academic papers—there are many—and odds are that you will find a least one unexpected insight. He was a cryptographer and security engineer, but also very much a generalist. He published on block cipher cryptanalysis in the 1990s, and the security of large-language models last year. He started conferences like nobody’s business. His masterwork book, Security Engineering—now in its third edition—is as comprehensive a tome on cybersecurity and related topics as you could imagine. (Also note his fifteen-lecture video series on that same page. If you have never heard Ross lecture, you’re in for a treat.) He was the first person to understand that security problems are often actually economic problems. He was the first person to make a lot of those sorts of connections. He fought against surveillance and backdoors, and for academic freedom. He didn’t suffer fools in either government or the corporate world.

He’s listed in the acknowledgments as a reader of every one of my books from Beyond Fear on. Recently, we’d see each other a couple of times a year: at this or that workshop or event. The last time I saw him was last June, at SHB 2023, in Pittsburgh. We were having dinner on Alessandro Acquisti‘s rooftop patio, celebrating another successful workshop. He was going to attend my Workshop on Reimagining Democracy in December, but he had to cancel at the last minute. (He sent me the talk he was going to give. I will see about posting it.) The day before he died, we were discussing how to accommodate everyone who registered for this year’s SHB workshop. I learned something from him every single time we talked. And I am not the only one.

My heart goes out to his wife Shireen and his family. We lost him much too soon.

EDITED TO ADD (4/10): I wrote a longer version for Communications of the ACM.