CryptoDB
François Gérard
Publications
Year
Venue
Title
2023
TCHES
High-order masking of NTRU
Abstract
The main protection against side-channel attacks consists in computing every function with multiple shares via the masking countermeasure. While the masking countermeasure was originally developed for securing block-ciphers such as AES, the protection of lattice-based cryptosystems is often more challenging, because of the diversity of the underlying algorithms. In this paper, we introduce new gadgets for the high-order masking of the NTRU cryptosystem, with security proofs in the classical ISW probing model. We then describe the first fully masked implementation of the NTRU Key Encapsulation Mechanism submitted to NIST, including the key generation. To assess the practicality of our countermeasures, we provide a concrete implementation on ARM Cortex-M3 architecture, and eventually a t-test leakage evaluation.
2022
EUROCRYPT
Mitaka: A Simpler, Parallelizable, Maskable Variant of Falcon
📺
Abstract
This work describes the Mitaka signature scheme: a new hash-and-sign
signature scheme over NTRU lattices which can be seen as a variant of
NIST finalist Falcon. It achieves comparable efficiency but is
considerably simpler, online/offline, and easier to parallelize and
protect against side-channels, thus offering significant advantages from
an implementation standpoint. It is also much more versatile in terms of
parameter selection.
We obtain this signature scheme by replacing the FFO lattice Gaussian
sampler in Falcon by the “hybrid” sampler of Ducas and Prest, for
which we carry out a detailed and corrected security analysis. In
principle, such a change can result in a substantial security loss, but
we show that this loss can be largely mitigated using new techniques in
key generation that allow us to construct much higher quality lattice
trapdoors for the hybrid sampler relatively cheaply. This new approach
can also be instantiated on a wide variety of base fields, in contrast
with Falcon's restriction to power-of-two cyclotomics.
We also introduce a new lattice Gaussian sampler with the same quality
and efficiency, but which is moreover compatible with the integral matrix
Gram root technique of Ducas et al., allowing us to avoid floating point
arithmetic. This makes it possible to realize the same signature
scheme as Mitaka efficiently on platforms with poor support for
floating point numbers.
Finally, we describe a provably secure masking of Mitaka. More precisely,
we introduce novel gadgets that allow provable masking at any order at much
lower cost than previous masking techniques for Gaussian sampling-based
signature schemes, for cheap and dependable side-channel protection.
2022
TCHES
High-order Table-based Conversion Algorithms and Masking Lattice-based Encryption
Abstract
Masking is the main countermeasure against side-channel attacks on embedded devices. For cryptographic algorithms that combine Boolean and arithmetic masking, one must therefore convert between the two types of masking, without leaking additional information to the attacker. In this paper we describe a new high-order conversion algorithm between Boolean and arithmetic masking, based on table recomputation, and provably secure in the ISW probing model. We show that our technique is particularly efficient for masking structured LWE encryption schemes such as Kyber and Saber. In particular, for Kyber IND-CPA decryption, we obtain an order of magnitude improvement compared to existing techniques.
2022
TCHES
High-order Polynomial Comparison and Masking Lattice-based Encryption
Abstract
The main protection against side-channel attacks consists in computing every function with multiple shares via the masking countermeasure. For IND-CCA secure lattice-based encryption schemes, the masking of the decryption algorithm requires the high-order computation of a polynomial comparison. In this paper, we describe and evaluate a number of different techniques for such high-order comparison, always with a security proof in the ISW probing model. As an application, we describe the full high-order masking of the NIST standard Kyber, with a concrete implementation on ARM Cortex M architecture, and a t-test evaluation.
2020
TCHES
Cortex-M4 optimizations for {R,M} LWE schemes
📺
Abstract
This paper proposes various optimizations for lattice-based key encapsulation mechanisms (KEM) using the Number Theoretic Transform (NTT) on the popular ARM Cortex-M4 microcontroller. Improvements come in the form of a faster code using more efficient modular reductions, optimized small-degree polynomial multiplications, and more aggressive layer merging in the NTT, but also in the form of reduced stack usage. We test our optimizations in software implementations of Kyber and NewHope, both round 2 candidates in the NIST post-quantum project, and also NewHope-Compact, a recently proposed variant of NewHope with smaller parameters. Our software is the first implementation of NewHope-Compact on the Cortex-M4 and shows speed improvements over previous high-speed implementations of Kyber and NewHope. Moreover, it gives a common framework to compare those schemes with the same level of optimization. Our results show that NewHope- Compact is the fastest scheme, followed by Kyber, and finally NewHope, which seems to suffer from its large modulus and error distribution for small dimensions.
Coauthors
- Erdem Alkim (1)
- Yusuf Alper Bilgin (1)
- Murat Cenk (1)
- Jean-Sébastien Coron (3)
- Thomas Espitau (1)
- Pierre-Alain Fouque (1)
- Simon Montoya (2)
- Mélissa Rossi (1)
- Akira Takahashi (1)
- Mehdi Tibouchi (1)
- Matthias Trannoy (1)
- Alexandre Wallet (1)
- Yang Yu (1)
- Rina Zeitoun (3)