20 Feb 2019
RAVENS is the result of my internship at Orange. The challenge this project is solving is updating the firmware of extremely small devices in a secure, resilient and efficient manner.
The project is open source, available on GitHub at https://github.com/Orange-OpenSource/RAVENS. We’re open to suggestions, and pull requests! 😀
RAVENS: Decompressing with only 4kB of memory
13 Mar 2019
When trying to port BSDiff to our platform, we encountered two main challenges. The first was performing the update in place, which resulted in us solving the WbR conflict problem. The second was a bit more intrinsic to the original approach: the idea of compressing part of the payload. Due to our highly stringent memory requirements (the target I had in mind was 16kB of RAM), we had to find a compression algorithm enabling decompression with very little memory, and very little access to the already decompressed data (we wanted to stream the decompressed data in the RAM buffer, not decompress the full payload).
RAVENS: How a small problem turned big, or the tale of WbR conflicts
6 Mar 2019
While working on the project that led to RAVENS, Write-before-Read (WbR) conflicts appeared a little bit out of nowhere and almost became a showstopper. The algorithm Hugin uses to get rid of them is by far the most complex and time intensive part of the whole project. In this article, I’ll try to describe why they are such a big deal, how we got rid of them and why it took me so long.
RAVENS: Securely transferring updates, with basically the whole world against you
27 Feb 2019
RAVENS was started in part as a security research project. Therefore, it has to go beyond simply installing an update, but also need to download it, in a potentially hostile environment.
Although this sounds like a solved problem (HTTPS!), this turned in a surprisingly complex problem when platform limitations had to be taken into account. Specifically, the devices we were targeting (that is, very low power devices powered by a monolithic MCU) may not have the memory to run a TLS stack.
RAVENS: Installing in-place updates, reliably
20 Feb 2019
The most obvious challenge is not always the hardest to solve. This is the case of reliable in-place updates. How does RAVENS manage to rewrite “itself”, even if power is cut?
Ground rules First, there is an important detail to note. Due to how limited are the devices that need this level of efficiency, the running program isn’t copied to RAM. This means that there are some ground rules: you can’t rewrite (i.
Upgrading a deprecated software or the tale of Flamingo (Part 1)
10 Sep 2016
TL;DR: Code is available on Github
Flamingo is a XMPP client released in 2012 which differentiate itself with a high quality design. Considering the competition consisted almost solely of Adium, a barely maintained, very old (probably the early OS X days) project based on libpurple. From a user experience perspective, Flamingo was light years ahead, but two problems prevented a migration to be a no brainer.
The future of computing
22 Mar 2016
The release of the new iPad Pro, coupled with Apple communications trying to sell old PC users to iPad sparked some new debates on whatever this platform will overtake the world given the proper tools (the most realistic one being Xcode for iPad and the ability to side load apps (on which I don’t agree but whatever)). I initially wanted to unleash my (hotter) take on Twitter but instead decided to take some time to put it down in clearer words.
Tracking a user in subway without GPS signal
1 Nov 2015
The subway is a strange place: very common in most of the large cities, faster and more reliable than busses, but yet, by its very nature, a challenge to use by navigation apps. By being underground most of the time, there is no GPS or WiFi signal, and LTE/3G is sporadic at best (beside a couple of cities, but far from the standard) and 2G signal would massively increase the battery strain. Moreover, I’m unsure the reception would be good enough to perform a localization precise enough. The builtin location service is thus out of question.
14 Nov 2012
I used to be a proud user of Firefox but updates after updates, the slowness finally kicked me out of its userbase
After that, I started to look for something else. And there is only one big opponent to Firefox: Chrome… But well, there is an issue.
I’m not a big fan of Google.