Forging RSA-PSS signatures with mbedTLS

This posts describes how to forge public-key signatures computed using mbedTLS’s implementation of RSA-PSS (the RSA-based standard signature scheme). Forging a signature means determining a valid signature of some message without knowing the secret key, but possibly know valid signatures of other messages. A signature scheme—or implementation thereof—is considered insecure if such forgeries are practical. … Continue reading Forging RSA-PSS signatures with mbedTLS

Defeating Quantum Algorithms with Hash Functions

In this post I'll explain why quantum computers are useless to find hash function collisions, and how we can leverage this powerlessness to build post-quantum signature schemes. I'll then describe a quantum computing model that you can try at home, and  one where hash function collisions are easy to find. Let me start with a few … Continue reading Defeating Quantum Algorithms with Hash Functions

When Constant-Time Source Code May Not Save You

On November 14 at CANS 2016 in Milan I presented a timing attack against an implementation of Curve25519 (also called X25519). This elliptic curve was designed by DJ Bernstein in order to provide a secure curve without probable NSA back doors and with safe computations. Additionally it was designed to be protected against state-of-the-art timing attacks. The targeted implementation called … Continue reading When Constant-Time Source Code May Not Save You

SANS Holiday Hack Challenge 2016

During my holiday I tackled the SANS HolidayHack challenge 2016. It was a lot of fun and a useful way of keeping my skills up to date. The goal of the challenge was to answer some questions and play a little game with a lot of quests made up of computer science challenges. I will publish just a condensed section … Continue reading SANS Holiday Hack Challenge 2016

Do not create a backdoor, use your provider’s one !

It was recently shown by the Mirai botnet or Linux/Moose worm that more and more connected devices can run a large scale DDoS. As an example, I'll provide here a small analysis showing that the problem is even more complicated since we sometimes have to live with old devices which have not been updated by Internet providers. A … Continue reading Do not create a backdoor, use your provider’s one !

iOS malware: myth or reality?

Introduction The 2015 DBIR report from Verizon contained a small section on mobile malware but the part on iOS said that all alerts on this platform were all false positives that were in fact triggered by Android devices ("most of the suspicious activity logged from iOS devices was just failed Android exploits"). This is great as … Continue reading iOS malware: myth or reality?

Spark Summit Europe 2016

I attended Spark Summit Europe 2016 in Brussels this year in October, a conference where Apache Spark enthusiasts meet up. I've been using Spark for nearly a year now on multiple projects and was delighted to see so many Spark users at Square Brussels. There were three trainings to choose from on the first day. I … Continue reading Spark Summit Europe 2016