Hey! I'm David, a security engineer at the Blockchain team of Facebook, previously a security consultant for the Cryptography Services of NCC Group. I'm also the author of the Real World Cryptography book. This is my blog about cryptography and security and other related topics that I find interesting.

# Sudoku Solver posted November 2013

My Programmmation class first part is about coding a sudoku solver. We have to do everything in english, we have to commit with svn, we have to write a final report with LaTeX.

Every week we're given some vague guidelines and we have to dive deep into C to first, understand what we have to do, and secondly, find solutions in a language we've never really played with before. We have to turn in what we did every week, if our code doesn't compile it's a zero, if it does compile it goes through a multitude of tests that quickly decrease your grade (out of 20). Let's just say I spent many nights and early mornings coding and I started the first week with a 2/20.

It felt like a crash course, it felt unfair at times, but holy cow did I learn some C in a really short amount of time. Props to my professor for that, and I wish I had more courses like that. I might not get the best grade out of this course but I sure learn the most things there.

I've also committed everything I've done on a public git repo so everyone can see how it looks like here :

https://github.com/mimoo/sudoku

You can compile with make, learn how to use with ./sudoku -h

It can read sudokus of different sizes from 1x1 to 64x64 as long as it is presented like this :

#this is a comment

5 3 _ _ 7 _ _ _ _

6 _ _ 1 9 5 _ _ _

_ 9 8 _ _ _ _ 6 _

8 _ _ _ 6 _ _ _ 3

4 _ _ 8 _ 3 _ _ 1

7 _ _ _ 2 _ _ _ 6

_ 6 _ _ _ _ 2 8 _

_ _ _ 4 1 9 _ _ 5

_ _ _ _ 8 _ _ 7 9

# Start of the school year posted September 2013

time table imported to google cal thanks to hackjack's fabulous application
I have at the moment 5 classes which are all taught in french (I guess because there are not enough foreigners this year), but some of them use english for their slides.

### Programmation

Nothing really new to me, some people coming from the same bachelor as I (mathematics) have difficulties getting to know Linux and programming as a whole for the first time. I'm used to coding so I'm pretty confident (I shouldn't relax too much though). We started on a fast-course on C, GCC, Emacs, SVN... and will move on later with Java. It's taught by Emmanuel Fleury who is a very chill professor, good vibe, very easy to talk to. And the best part is that everything he talks about is online here so if you're interested in the course I'm taking you can have a look there. PS: we're learning a bit of LaTeX AND will have to submit final reports in LaTeX. This is great as I have sought a good occasion to learn it for a while. PS2: I'm using LearnXinYminutes.com to get back into C (haven't coded in C for more than 4 years). It's a great website and I recommend it to you if you want to learn something about any language and already have knowledge in programming.

### Théorie de l'information

Taught by the head of the Cryptology Master, Gilles Zemor, the course seems like an introduction to some of the concepts around Cryptography. Our first classes were about Entropy (which I talked about a bit in the previous post) and easy notions of probability. Here are the professor's notes about the course.

### Arithmétique

The only "real" Math course we have, and I'm a bit surprised since this is a "Mathematics" Master". It's essentially about rings, it's about stuff I already learned. Nothing really captivating at the moment.

### Automates et Complexité

This is one of the most intriguing course, people coming from an IT bachelor seem to have no problem with it. I don't really understand the point of learning this but I like it, it's a lot like Regular Expressions and is about logic more than learning concepts by heart. As a programmer it just seems like funny games to me :) (it might get more difficult very quickly). Note : it's taught by Anca Muscholl.

### Réseaux

The only course I had to choose, but we didn't have much choice since they removed half of the available courses including the one I wanted to take (Probability). The course is taught by... it's a rapid introduction about network concept. I'm not really into it, it speaks too briefly about many things, some are interesting, some are not. I was supposed to have an application class but apparently our professor fell asleep on his way (he's narcoleptic). Overall I was surprised by the absence of real "cryptology courses". But the professors told us they would come very quickly in the second semester, so nothing to worry about. comment on this story

# Here we go posted August 2013

Hey guys, I'm David Wong, a 24 years old french dude who's going to start a Master of Cryptology in the university of Bordeaux 1.

Cryptology (or as Americans like to call it: Cryptography, because we all know they don't care about etymology) is the study of the techniques for secure communications (thanks Wikipedia!), from withdrawing money with a fake credit card to establishing a safe phone conversation between two government officials, it can mean a lot of things... I still have no clue what my future job will be, that's why I had the idea of making this small blog where I could post about my ventures into this new world and, hopefully, being able to take a step back and see what I did, what I liked, what happened in two years of Master (and maybe more).

I've already took Cryptography I given by Dan Boneh from Stanford and I must say I really enjoyed going through his course. Might be one of the most interesting and eloquent teacher I had in my life, and I have never met him. Had a few back and forth mail exchanges with him but sadly, there was no collaboration between our universities. California I'll see you later in life I guess.

I'll also post some thoughts about the new city I'll be moving to : Bordeaux. This is for at least 2 years, or less if I change my mind. Anyway, this is going to be exciting!