Description
Quasi-cyclic moderate density parity check (QC-MDPC) codes allow the design of McEliece-like public-key encryption schemes with compact keys and a security that provably reduces to hard decoding problems for quasi-cyclic codes. Because of these features, QC-MDPC have attracted a lot of interest from the cryptographic community. In particular, the BIKE suite of key exchange mechanisms has been selected to the second round of the NIST call for standardization of quantum safe cryptographic primitives.<br/> To reach IND-CCA security, it is necessary to prove that the decoding failure rate (DFR) is negligible. Getting a formal proof of a low DFR is a difficult task. Instead, we propose to ensure this low DFR under some additional security assumption on the decoder. This assumption relates to the asymptotic behavior of the decoder and is supported by several other works. We thus evaluate a decoder by simulation and extrapolate its DFR under the decoder security assumption. Using standard techniques from communication systems, we can evaluate the confidence in our extrapolation.<br/> The construction of a set of weak keys, in the sense that they have a higher DFR, has been exhibited in a recent work [Drucker, Gueron, Kostic 2019]. We observe that these keys are related to the key recovery reaction attack of [Guo, Johansson, Stankovski 2016] by the fact that they have an atypical "spectrum". From this observation, we can generalize the construction by directly generating keys with an atypical spectrum. Using combinatorics to count these weak keys and applying our methodology to evaluate the DFR, we prove that they do not affect the security of the scheme.<br/> lien: http://desktop.visio.renater.fr/scopia?ID=723203***9541&autojoin
Next sessions
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Post-Quantum Public-Key Pseudorandom Correlation Functions for OT
Speaker : Mahshid Riahinia - ENS, CNRS
Public-Key Pseudorandom Correlation Functions (PK-PCF) are an exciting recent primitive introduced to enable fast secure computation. Despite significant advances in the group-based setting, success in the post-quantum regime has been much more limited. In this talk, I will introduce an efficient lattice-based PK-PCF for the string OT correlation. At the heart of our result lie several technical[…] -
Predicting Module-Lattice Reduction
Speaker : Paola de Perthuis - CWI
Is module-lattice reduction better than unstructured lattice reduction? This question was highlighted as `Q8' in the Kyber NIST standardization submission (Avanzi et al., 2021), as potentially affecting the concrete security of Kyber and other module-lattice-based schemes. Foundational works on module-lattice reduction (Lee, Pellet-Mary, Stehlé, and Wallet, ASIACRYPT 2019; Mukherjee and Stephens[…]-
Cryptography
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Attacking the Supersingular Isogeny Problem: From the Delfs–Galbraith algorithm to oriented graphs
Speaker : Arthur Herlédan Le Merdy - COSIC, KU Leuven
The threat of quantum computers motivates the introduction of new hard problems for cryptography.One promising candidate is the Isogeny problem: given two elliptic curves, compute a “nice’’ map between them, called an isogeny.In this talk, we study classical attacks on this problem, specialised to supersingular elliptic curves, on which the security of current isogeny-based cryptography relies. In[…]-
Cryptography
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