Program

Simona Samardjiska, Radboud University

Title: 

Algebraic Methods in code-based cryptography

Abstract:

 Code-based cryptography has been around for quite a while with the McEliece cryptosystem using the syndrome decoding problem in the Hamming metric considered one of the best understood cryptosystems with stable record of cryptanalytical advancement.  The best attacks are still message recovery attacks that use combinatorial methods against the underlying hard problem. 

In recent years, the quest for better performance has made the code-based scene much more colorful with abundance of new metrics, new hard problems and cryptographic constructions. As a result, the cryptanalytic methods are also more varied with algebraic methods becoming more relevant and more creative.

In this talk I will give an overview of algebraic attacks used in code-based cryptography. On a high level, such an attack involves modeling a hard problem or a cryptosystem as a  system of equations and then solving it. The challenge lies in finding the best possible algebraic model and the best possible solving method. I will go through several examples of algebraic modeling and solving of hard problems, decryption errors and cryptographic construction. I will further argue that often, a clever  combination of algebraic and combinatorial methods yields the best results.

Alexander May, Ruhr University Bochum

Title: 

Hints for Codes and Lattices

Abstract:

Implementations may leak partial information of cryptographic secret key, e.g. via side-channel analysis. Such partial information is usually called a hint. It is of crucial importance to understand to which extent hints decrease the security of cryptographic constructions. As a consequence, the security loss of cryptographic keys under various hints has been intensively studied within the last decade. 

This talk gives a survey of hints considered in the coding as well as in the lattice world. For codes we review the hint framework  introduced by Horlemann, Puchinger, Renner, Schamberger, Wachter-Zeh (CBCrypto 21), and compare it to the lattice-based frameworks of Dachman-Soled, Ducas, Gong, Rossi (Crypto 20), Dachman-Soled, Gong, Hanson, Kippen (Crypto 23) and May, Nowakowski (Asiacrypt 23). We also provide some practical applications of hints, e.g. their use in the cryptanalysis of McEliece-1284 by Esser, May and Zweydinger (Eurocrypt 22).