Icy-DVRF: A Distributed Verifiable Random Function Based on FROST Signatures

Subtitle: A FROST-based Threshold Schnorr Signature Scheme with Identifiable Aborts and Fully Adaptive Security from AOMDL

Verifiable Random Sampling

This work proposes a concrete VRS construction based on random quantum circuit sampling (RCS) executable on today's quantum computing devices and model the construction and prove its security within the constructive cryptography (CC) framework, thereby ensuring composability with other cryptographic protocols.

A Practical Dynamic Searchable Symmetric Encryption Scheme With Trusted Hardware-Assisted

Side-Channel Secure CSIDH with Projective Coordinates

CSIDH is an isogeny-based Non-Interactive Key Exchange (NIKE) proposed at ASIACRYPT'18. In this work, we present the first masked version of CSIDH and, in fact, any isogeny-based scheme. We develop gadgets to efficiently mask all arithmetics in the underlying finite field and prove them secure in the d -probing model. In particular, we develop new gadgets for the Montgomery ladder using the fact that projective values already represent a multiplicative sharing in two variables. The technique (dubbed quotient masking) might be of independent interest. Lastly, we provide an efficient implementation based on High-Security CSIDH (Communications in Cryptology 2024). We show that the relative computational overhead of masking the latter—compared to other state-of-the-art CSIDH implementations—is similar to other masked implementations of post-quantum cryptography primitives.

Compressed Key Exchange Protocol from Orientations of Large Discriminant Using AVX-512

CSIDH (Commutative Supersingular Isogeny Diffie–Hellman) is a classgroup- based key-exchange protocol operated on supersingular elliptic curves, which, at the time of its proposal, exhibited several attractive selling points such as noninteractivity. Unfortunately, CSIDH is vulnerable to the sub-exponentiation attack– Kuperberg’s algorithm, thereby requiring large parameters to ensure security. A recent work based on oriented elliptic curves with large discriminants, proposed by Houben, allows for a significantly small base field (around 255 bits). We name this protocol CSIDH-LDO. However, the practicality of CSIDH-LDO is currently hindered by the necessity of performing multiple group actions and its huge public-key size.In this paper, we address these bottlenecks by presenting highly optimized constanttime implementations alongside an effective public-key compression framework for CSIDH-LDO. We combine algorithmic improvements, specifically scalar multiplication by differential addition chains and isogeny computation on the twisted Edwards model, with limb-slicing to exploit parallelism via Intel’s AVX-512 instructions. To resolve the architectural mismatch when mapping r ∈ {7, 13} group actions to 8-lane SIMD registers, we evaluate two parallel scheduling strategies. While a dummy-based approach allows us to leverage efficient Fp2-arithmetic, our dummy-free strategy systematically exploits internal parallelism to fully saturate the 512-bit vectors without redundant computations. Benchmarks on an Intel Tiger Lake processor demonstrate our parallel implementations achieve speedups of up to 3.40x (AVX-512F) and 7.30x (AVX-512IFMA) over an optimized x64 assembly baseline. Furthermore, we establish a formal framework for public-key compression tailored for CSIDH-LDO. Specifically, we propose two efficient techniques that achieve a compact public key representation of approximately (r + 2) log2(p) bits, thereby significantly reducing communication bandwidth. To the best of our knowledge, this work is the first to demonstrate the efficacy of SIMD parallelization combined with optimized compression for isogenybased protocols derived from orientations of large discriminants.

Quantum-safe DualRing with shorter signature and public key

With the standardization of post-quantum signature schemes such as Dilithium and Falcon, lattice-based ring signatures have become a promising tool for anonymous authentication and privacy-preserving encryption in big data environments. Specifically, the DualRing-LB scheme (CRYPTO’ 21), despite its short signatures and elegant structure, suffers from the large public key size, which dominates its communication cost and hinders scalability. There are two methods to reduce the public key size: the first is a compression technique, and the second is the bimodal distribution. The former discards the lower bits of the public key while the latter utilizes a smaller modulus. However, the unforgeability proof of DualRing-LB is incompatible with these methods because they lead to a rapid increase in the norm bound of the module short integer solution (or MSIS) problem, thereby significantly reducing security. In this paper, we follow the original security method of DualRing-LB and apply the trapdoor sampling technique to derive a tighter upper bound of MSIS problem, yielding a fixed security level independent of the ring size. The new proof result enables the use of both the compression technique and the bimodal distribution to enhance the communication efficiency of lattice-based DualRing schemes. Based on this result, we propose three practical lattice-based instantiations that reduce the public key size by 56%, 67%, 50%, compared to DualRing-LB, respectively, and achieve overall size reductions of at least 52%, 56%, 38%, respectively, across different ring sizes. Our results can contribute to lightweight, privacy-preserving cryptographic mechanisms for secure data sharing and authentication in large-scale distributed systems.