Section: Highlights of the Year

Highlights of the Year

The end of this year was the deadline to submit proposals to the NIST competition  (https://csrc.nist.gov/projects/post-quantum-cryptography/post-quantum-cryptography-standardization), whose purpose is to standardize quantum-safe public-key primitives. This call concerns all three major cryptographic primitives, namely public-key cryptosytems, key-exchange protocols and digital signature schemes. The most promising techniques today for addressing this issue are code-based cryptography, lattice-based cryptography, mutivariate cryptography, and hash-based cryptography.

We have contributed to three proposals to the NIST call. In two of them, “BIKE” [67] and “Big Quake” [69], our action is central and we also have a marginal participation in another, “Classic McEliece”. Those projects are of great importance for us because they are a means to demonstrate our long lasting expertise in code-based cryptography. They are the product of numerous research works, including several PhD theses, on the design, the implementation, and the cryptanalysis of code-based cryptographic primitives. There are 69 projects in that call, which will be evaluated by the NIST and the academic cryptographic community in the next three to five years and whose outcome will certainly influence cryptographic applications for one or several decades.

The resistance of symmetric primitives to quantum computers is a topic that has received recently a lot of attention from our community. The ERC starting grant QUASYModo on this subject, awarded to M. Naya-Plasencia, has started in September 2017. We have continued the work started last year obtaining new results, as cryptanalysis of concrete proposals [44], or analysis on attacks considering modular additions (preliminary described in [14]). In particular, we have proposed in [47] a new quantum algorithm for finding collisions. This new algorithm, based on BHT, exploits distinguished points as well as an improved optimization of the parameters, and allows to find for the first time, collisions on $n$ bits with a better time complexity than $2^{n/2}$. Its time and query complexity are of about $2^{2n/5}$, needing $2^{n/5}$ classical memory and a polynomial amount of quantum memory. As collision search is a tool widely used in symmetric cryptanalysis, this algorithm, that also can be applied to multiple preimage search, considerably improves the best known previous attacks when having a relatively small quantum computer available.