Description
The Quantum Fourier Transform is a fundamental tool in quantum cryptanalysis, not only as the building block of Shor's algorithm, but also in attacks against symmetric cryptosystems. Indeed, hidden shift algorithms such as Simon's (FOCS 1994), which rely on the QFT, have been used to obtain attacks on some very specific block cipher structures. The Fourier Transform is also used in classical cryptanalysis, for example in FFT-based linear key-recovery attacks introduced by Collard et al. (ICISC 2007). Whether such techniques can be adapted to the quantum setting has remained so far an open question. In this talk, we will present a new framework for quantum linear key-recovery attacks using the QFT. These attacks loosely follow the classical method of Collard et al., but adapt it to the quantum setting. Classically, the FFT-based attack needs to compute a statistic (experimental correlation) which is higher for a good key guess, and lower for wrong guesses. The quantum attack encodes this statistic in the amplitudes of a quantum state. On some conditions, this can be used to devise new quantum key-recovery attacks which may be applicable to a broader class of ciphers.
Prochains exposés
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Efficient zero-knowledge proofs and arguments in the CL framework
Orateur : Agathe Beaugrand - Institut de Mathématiques de Bordeaux
The CL encryption scheme, proposed in 2015 by Castagnos and Laguillaumie, is a linearly homomorphic encryption scheme, based on class groups of imaginary quadratic fields. The specificity of these groups is that their order is hard to compute, which means it can be considered unknown. This particularity, while being key in the security of the scheme, brings technical challenges in working with CL,[…] -
Constant-time lattice reduction for SQIsign
Orateur : Sina Schaeffler - IBM Research
SQIsign is an isogeny-based signature scheme which has recently advanced to round 2 of NIST's call for additional post-quantum signatures. A central operation in SQIsign is lattice reduction of special full-rank lattices in dimension 4. As these input lattices are secret, this computation must be protected against side-channel attacks. However, known lattice reduction algorithms like the famous[…] -
Circuit optimisation problems in the context of homomorphic encryption
Orateur : Sergiu Carpov - Arcium
Fully homomorphic encryption (FHE) is an encryption scheme that enables the direct execution of arbitrary computations on encrypted data. The first generation of FHE schemes began with Gentry's groundbreaking work in 2019. It relies on a technique called bootstrapping, which reduces noise in FHE ciphertexts. This construction theoretically enables the execution of any arithmetic circuit, but[…] -
TBD
Orateur : Maria Corte-Real Santos - ENS Lyon
TBD-
Cryptography
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