An Anomalous Differential Attack on a Block Cipher

In this attack a differential propagates with difficulty for some 20, 40 and up to 64 rounds. We can say that the propagation encounters some “friction”, because the non-linear functions do not always behave as the attacker would like them to behave. Everything looks normal and this is what happens for all block ciphers all …

Continue reading ‘An Anomalous Differential Attack on a Block Cipher’ »

Hacking a Linux PC at a Close Distance without Being Connected to a Network

The attack allows the attacker to execute arbitrary code on another PC running Linux. The exploit is possible due to an extremely serious vulnerability in Bluetooth stack inside Linux. The attacker literally can run an application of his choice on the other PC. The exploit was found by Andy Nguyen, a security researcher at Google. …

Continue reading ‘Hacking a Linux PC at a Close Distance without Being Connected to a Network’ »

A New Documentary about WW2 Cryptanalysis of Enigma

A new documentary tells the story of the discovery of one of the most important cryptography papers of all times. We are talking about an extensive technical report written in German language and entitled “Kurzgefasste Darstellung der Auflösungsmethoden”. For some 80 years it has remained classified, part of the so called Gustave Bertrand WW2 archives. It was …

Continue reading ‘A New Documentary about WW2 Cryptanalysis of Enigma’ »

A Linear Annihilator Property and Strong Biases with Original DES S-boxes

In 2004 I have published a paper [Crypto 2004, Santa Barbara] in which I explain the concept of the so called Bi-Linear attack on DES. The old attack was not extremely strong. It is possible to see that two conditions would be necessary for such an attack to somewhat work well in cryptanalysis of DES: There …

Continue reading ‘A Linear Annihilator Property and Strong Biases with Original DES S-boxes’ »

How to Backdoor a Block Cipher

I have written an elementary tutorial and a first proof of concept about how to backdoor a block cipher in a quite general setting. Potentially it applies to any block cipher. Success is not guaranteed though, see the paper. ADDED 2 JAN 2019: a new paper shows that invariants of higher degree are substantially more powerful. …

Continue reading ‘How to Backdoor a Block Cipher’ »

UCL InfoSec Visit at Bletchley Park – Friday 29 Sept 2017

Our trip took place 29 Sept 2017.  Some 32 UCL students participated. Students have explored the past in order to find role models for the future.           Due to large numbers, we have split into two groups for a guided Bletchley Park tour, and also had assisted at two bombe demonstrations. …

Continue reading ‘UCL InfoSec Visit at Bletchley Park – Friday 29 Sept 2017’ »

How Many 1024-bit Primes Have Backdoors?

So how did the NSA backdoored the Internet or did they??? New ground-breaking paper shows that DSA and DH mod P keys with 1024 bits are vulnerable to practical backdoors which can be exploited to break our secure communications. Few highlights: For such trapdoored primes the DL problem can be solved in 2 months by an academic cluster. The …

Continue reading ‘How Many 1024-bit Primes Have Backdoors?’ »

UCL InfoSec Visit at Bletchley Park – 2 Oct 2016

    Home Work After a bombe demonstration by a WW2 veteran Ruth Bourne and BP bombe experts, students have been asked to further study at home how Enigma was broken, see our hand-out. More details can be found in our teaching materials “Enigma and Block Ciphers – 100 years of cryptanalysis with non-commutative combinations …

Continue reading ‘UCL InfoSec Visit at Bletchley Park – 2 Oct 2016’ »

Researchers in Cryptography vs. Big Brother

For decades the dominant paradigm in crypto and security research would be: to claim that security vulnerabilities occur accidentally, ignoring major questions such as why there are so many of them and why the “bad scenarios” repeat so many times, concentrate security research on topics of secondary importance, or those which have no importance whatsoever and …

Continue reading ‘Researchers in Cryptography vs. Big Brother’ »