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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16 Sep 2020 : Contrac 0.6.2 released #
I've just pushed the latest changes to github and made Contrac 0.6.2 available from OpenRepos. This update adds new Chinese translations and fixes a bug that prevented the update button from being used daily (a borked calculation meant you could only update every two days, or thereabouts).
14 Sep 2020 : Contrac 0.6.1 released #
After a busy weekend of work, Contrac 0.6.1 is now available from OpenRepos and with code on github. The latest improvements include Chinese translations (thanks to the sterling work of dashinfantry) a homescreen cover, attenuation value configuration, and risk configuration downloaded from the Corona-Warn-App servers to ensure the risk evaluations mirror the official app.
6 Sep 2020 : Contrac 0.5.1 released #
The latest version of Contrac now analyses the keys downloaded from the server against thoe collected using Bluetooth and provides an up-to-date risk assessment for the user. This is a pretty big step, because it means the app now has all the pieces needed to perform the full exposure notification cycle (diagnosis upload, key download, exposure analysis). There are still plenty of potential improvements of course, the main one being that it needs to be plugged in to the official severs rather than my test server, but hopefully that'll come soon. In the meantime, get it from OpenRepos and github.
1 Sep 2020 : Contrac 0.4.1 released #
Version 0.4.1 of Contac, an exposure notification app compatible with Germany's Covid-Warn-App is now available from OpenRepos and github. This latest version adds a bunch of improvements behind-the-scenes, including the encrypted metadata component of the BLE beacons and an improved data aggregation algorithm.
24 Aug 2020 : Contrac 0.3.1 alpha now available #
The new version of Contrac is now available from OpenRepos and github. This is a small, but hopefully useful, update. The daemon now has persistent state, so if it's set to scan/advertise for beacons it will remain in that state even after a restart.