ePrint Report: Isogeny-based Cryptography using Isomorphisms of Superspecial Abelian Surfaces Pierrick Gaudry, Julien Soumier, Pierre-Jean Spaenlehauer We investigate the algorithmic problem of computing isomorphisms between products of supersingular elliptic curves, given their endomorphism rings. This computational problem seems to be difficult when the domain and codomain are fixed, whereas we provide efficient algorithms to compute…

ePrint Report: Distributional Private Information Retrieval Ryan Lehmkuhl, Alexandra Henzinger, Henry Corrigan-Gibbs A private-information-retrieval (PIR) scheme lets a client fetch a record from a remote database without revealing which record it fetched. Classic PIR schemes treat all database records the same but, in practice, some database records are much more popular (i.e., commonly fetched) than…

ePrint Report: Cryptanalysis of an Efficient Signature Based on Isotropic Quadratic Forms Henry Bambury, Phong Q. Nguyen We present a key-recovery attack on DEFI, an efficient signature scheme proposed recently by Feussner and Semaev, and based on isotropic quadratic forms, borrowing from both multivariate and lattice cryptography. Our lattice-based attack is partially heuristic, but works…

ePrint Report: TockOwl: Asynchronous Consensus with Fault and Network Adaptability Minghang Li, Qianhong Wu, Zhipeng Wang, Bo Qin, Bohang Wei, Hang Ruan, Shihong Xiong, Zhenyang Ding BFT protocols usually have a waterfall-like degradation in performance in the face of crash faults. Some BFT protocols may not experience sudden performance degradation under crash faults. They achieve…

ePrint Report: DewTwo: a transparent PCS with quasi-linear prover, logarithmic verifier and 4.5KB proofs from falsifiable assumptions Benedikt Bünz, Tushar Mopuri, Alireza Shirzad, Sriram Sridhar We construct the first polynomial commitment scheme (PCS) that has a transparent setup, quasi-linear prover time, $log N$ verifier time, and $log log N$ proof size, for multilinear polynomials of…

ePrint Report: Symmetric Perceptrons, Number Partitioning and Lattices Neekon Vafa, Vinod Vaikuntanathan The symmetric binary perceptron ($mathrm{SBP}_{kappa}$) problem with parameter $kappa : mathbb{R}_{geq1} to [0,1]$ is an average-case search problem defined as follows: given a random Gaussian matrix $mathbf{A} sim mathcal{N}(0,1)^{n times m}$ as input where $m geq n$, output a vector $mathbf{x} in {-1,1}^m$…

ePrint Report: On the Anonymity of Linkable Ring Signatures Xavier Bultel, Charles Olivier-Anclin Security models provide a way of formalising security properties in a rigorous way, but it is sometimes difficult to ensure that the model really fits the concept that we are trying to formalise. In this paper, we illustrate this fact by showing…

ePrint Report: A Revision of CROSS Security: Proofs and Attacks for Multi-Round Fiat-Shamir Signatures Michele Battagliola, Riccardo Longo, Federico Pintore, Edoardo Signorini, Giovanni Tognolini Signature schemes from multi-round interactive proofs are becoming increasingly relevant in post-quantum cryptography. A prominent example is CROSS, recently admitted to the second round of the NIST on-ramp standardisation process for…

ePrint Report: Asynchronous YOSO a la Paillier Ivan Bjerre Damgård, Simon Holmgaard Kamp, Julian Loss, Jesper Buus Nielsen We present the first complete asynchronous MPC protocols for the YOSO (You Speak Only Once) setting. Our protocols rely on threshold additively homomorphic Paillier encryption and are adaptively secure. We rely on the paradigm of Blum et…

ePrint Report: A Privacy Model for Classical & Learned Bloom Filters Hayder Tirmazi The Classical Bloom Filter (CBF) is a class of Probabilistic Data Structures (PDS) for handling Approximate Query Membership (AMQ). The Learned Bloom Filter (LBF) is a recently proposed class of PDS that combines the Classical Bloom Filter with a Learning Model while…