I'm David Llewellyn-Jones and this is my homepage. I'm a software engineer at Jolla, who's also interested in programming, security, privacy and graphics. I occasionally crave adventure and a good thunderstorm. You might be interested in my software, my research or my random musings.

Want to know more about me? Here's a personality sketch written by a psychologist when I was in school.

“David is of high intelligence, although lacking in true creativity. He has a need for order and clarity, and for neat and tidy systems in which every detail finds its appropriate place. His writing is rather dull and mechanical, occasionally enlivened by somewhat corny puns and by flashes of imagination of the sci-fi type. He has a strong drive for competence. He seems to have little feel and little sympathy for other people and does not enjoy interacting with others. Self-centered, he nonetheless has a deep moral sense.”

Wow. Harsh. But disturbingly accurate.

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4 Jul 2020 : Waste data dump #
It's been a pretty good fortnight as far as my waste output is concerned. Plastic and general waste are up slightly, but that's counterbalanced with no metal or glass used this fortnight at all, bringing my daily average to 157g/day over the last two weeks. I'm happy with that.
20 Jun 2020 : Waste data dump #
My latest waste data dump just has been uploaded. My daily average over the last fortnight was 162g per day, which is a generally decent result for me. My goal is less than 300g, and during lockdown I've been closer to 150g, but a month ago it looked like things were creeping up. I'm much happier with 162g. That sets my 2020 average to date at 199g per day, compared to 304g in 2019. Breaking it down, my plastic output was rather high this fortnight. This is a bit of a cycle, because I buy many products in plastic containers (cosmetics; foods; cleaning products) which often last more than a fortnight. Returnables is also up because in the hot weather I'm buying more drinks. This was counterbalanced by less card and paper although I'm not really sure why to be honest.
7 Jun 2020 : Waste data dump #
I've uploaded another fortnight of waste data, up on my waste data page. The last two weeks haven't been so great again, with my daily average of 258g/day. That's below my target, and below the previous fortnight, but still well above my output level from a month ago, which was closer to 150g/day. The change has been driven by a few exceptional items in the card and compost categories making it into the bin; I need to make sure exceptional doesn't become routine.
1 Jun 2020 : Deploying authentication in the wild: Towards greater ecological validity in security usability studies #
Finally it looks like the last of the Pico papers, written with my co-authors Seb Aebischer, Claudio Dettoni, Graeme Jenkinson, Kat Krol, Toshiyuki Masui and Frank Stajano, and which has been working its way through the review process for many months, will finally be published. The paper is called "Deploying authentication in the wild: Towards greater ecological validity in security usability studies" and it describes the results — and challenges — of our usability trials of the Pico password replacement app. The details are now on my publications page and there's also a preprint.
24 May 2020 : Waste data dump #
This week was not a great waste output week. My average was 289g/day, only just below my 300g target. Mostly that's the product of me taking some time out with Joanna, meaning bottles of drink and a single-use escape room game with lots of packaging.