CryptoDB
Paul Frixons
Publications
Year
Venue
Title
2024
CIC
Block Cipher Doubling for a Post-Quantum World
Abstract
<p> In order to maintain a similar security level in a post-quantum setting, many symmetric primitives should have to double their keys and increase their state sizes. So far, no generic way for doing this is known that would provide convincing quantum security guarantees. In this paper we propose a new generic construction, QuEME, that allows one to double the key and the state size of a block cipher in such a way that a decent level of quantum security is guaranteed. The QuEME design is inspired by the ECB-Mix-ECB (EME) construction, but is defined for a different choice of mixing function than what we have seen before, in order to withstand a new quantum superposition attack that we introduce as a side result: this quantum superposition attack exhibits a periodic property found in collisions and breaks EME and a large class of its variants. We prove that QuEME achieves n-bit security in the classical setting, where n is the block size of the underlying block cipher, and at least (n/6)-bit security in the quantum setting. We finally propose a concrete instantiation of this construction, called Double-AES, that is built with variants of the standardized AES-128 block cipher. </p>
2024
CIC
Attacking trapdoors from matrix products
Abstract
<p> Recently, Geraud-Stewart and Naccache proposed two trapdoors based on matrix products. In this paper, we answer the call for cryptanalysis. We explore how using the trace and determinant of a matrix can be used to attack their constructions. We fully break their first construction in a polynomial-time attack. We show an information leak in the second construction using characteristic polynomials, and provide two attacks that decrease the bit security by about half. </p>
Coauthors
- Ritam Bhaumik (1)
- André Chailloux (1)
- Thomas Decru (1)
- Tako Boris Fouotsa (1)
- Paul Frixons (2)
- Valerie Gilchrist (1)
- Bart Mennink (1)
- María Naya-Plasencia (1)
- Christophe Petit (1)