Fully Homomorphic Encryption (FHE) enables arbitrary and unlimited computations directly on encrypted data. Notably, the TFHE scheme allows users to encrypt bits or small numbers (4-6 bits) and compute any univariate function using programmable bootstrapping (PBS), while simultaneously refreshing the ciphertext noise. Since both linear and non-linear functions can be evaluated using PBS, it is possible to compute arbitrary functions and circuits of unlimited depth without any accuracy loss....

Lattices are the basis of most NIST-recommended post-quantum cryptography (PQC) schemes, required to thwart the threat posed by the eventual construction of large-scale quantum computers. At the same time, lattices enable more advanced cryptographic constructions, such as fully homomorphic encryption (FHE), which is increasingly used for privacy-preserving applications like machine learning. This work delves into the efficiency and trade-off assessment of polynomial multiplication algorithms...

In recent years, online anonymity has become increasingly important but is under threat due to the challenges of moderating anonymous spaces. A promising cryptographic solution, known as anonymous blocklisting, allows users to post anonymously while still enabling moderation. Moderation via anonymous blocklisting roughly works by requiring that when users post a message they attach a cryptographic proof that they did not author any posts on a “blocklist”. Existing anonymous blocklisting...

Zero-Knowledge Proof (ZKP) is a cornerstone technology in privacy-preserving computing, addressing critical challenges in domains such as finance and healthcare by ensuring data confidentiality during computation. However, the high computational overhead of ZKP, particularly in proof generation and verification, limits its scalability and usability in real-world applications. Existing efforts to accelerate ZKP primarily focus on specific components, such as polynomial commitment schemes or...

Mix networks (mixnets) offer robust anonymity even against adversaries monitoring all network links; however, they impose high latency on communications. To address this, recent research has explored strategic low-latency routing within mixnets. While these strategies appear to reduce latency, their impact on mixnet anonymity has not been carefully assessed, raising concerns about potential deanonymization of clients. Tackling this challenge, this paper first quantifies the anonymity loss...

A group signature scheme enables users of a group to anonymously sign messages on behalf of the group, while a designated authority can revoke anonymity when needed to ensure user accountability. Among group signature schemes, fully dynamic ones are particularly desirable as they allow new users to join and misbehaved existing users to be revoked without requiring system-wide updates. This paper introduces DGSP, a post-quantum fully dynamic group signature scheme that addresses key...

This work addresses the hintless single-server Private Information Retrieval (PIR) from the perspective of high-level protocol design and introduces PIRCOR and PIRCOR$^{*}$ that outperform the state-of-the-art PIRANA (Liu et. al., IEEE S&P 2024) and YPIR (Menon and Wu, USENIX Security 2024) in terms of the query size and the query generation time. In PIRCOR, we construct an efficient Rotation-based Expanded Binary Code (REBC) to expand $\alpha$ primary codewords into $\beta$ expanded...

Smart contracts are integral to decentralized systems like blockchains and enable the automation of processes through programmable conditions. However, their immutability, once deployed, poses challenges when addressing errors or bugs. Existing solutions, such as proxy contracts, facilitate upgrades while preserving application integrity. Yet, proxy contracts bring issues such as storage constraints and proxy selector clashes - along with complex inheritance management. This paper introduces...

Range counting is the problem of preprocessing a set $P\subset R^d$ of $n$ points, such that given a query range $\gamma$ we can efficiently compute $|P\cap\gamma|$. In the more general range searching problem the goal is to compute $f(P\cap\gamma)$, for some function $f$. It was already shown (Kushnir et al. PETS'24) how to efficiently answer a range searching query under FHE using a technique they called Copy-and-Recurse to traverse partition trees. In the Range emptiness problem the...

Secure rate-distortion-perception (RDP) trade-offs arise in critical applications, such as semantic compression and privacy-preserving generative coding, where preserving perceptual quality while minimizing distortion is vital. This paper studies a framework for secure RDP over noiseless and noisy broadcast channels under strong secrecy constraints. We first characterize the exact secure RDP region for noiseless transmission channels. We then develop an inner bound on the secure RDP region...

Quantum computers leverage qubits to solve certain computational problems significantly faster than classical computers. This capability poses a severe threat to traditional cryptographic algorithms, leading to the rise of post-quantum cryptography (PQC) designed to withstand quantum attacks. FALCON, a lattice-based signature algorithm, has been selected by the National Institute of Standards and Technology (NIST) as part of its post-quantum cryptography standardization process. However, due...

The Classic McEliece key encapsulation mechanism (KEM), a candidate in the fourth-round post-quantum cryptography (PQC) standardization process by the National Institute of Standards and Technology (NIST), stands out for its conservative design and robust security guarantees. Leveraging the code-based Niederreiter cryptosystem, Classic McEliece delivers high-performance encapsulation and decapsulation, making it well-suited for various applications. However, there has not been a systematic...

Safeguarding cryptographic implementations against the increasing threat of Side-Channel Analysis (SCA) attacks is essential. Masking, a countermeasure that randomizes intermediate values, is a cornerstone of such defenses. In particular, SCA-secure implementation of AES, the most-widely used encryption standard, can employ Boolean masking as well as multiplicative masking due to its underlying Galois field operations. However, multiplicative masking is susceptible to vulnerabilities,...

Private information retrieval (PIR) enables a client to retrieve data from a server while preserving the confidentiality of the client's query. When PIR is instantiated with fully homomorphic encryption (FHE), the protocol becomes non-interactive, requiring only a query-answer exchange, and it achieves asymptotically optimal communication and computation complexity. Although several FHE-based PIR protocols have been practically implemented with the desired properties, there has been little...

Scloud$^{+}$ is a next-generation post-quantum key encapsulation mechanism that combines unstructured-LWE and a ternary key encoding technique to achieve efficient lattice cryptographic operations while eliminating traditional ring structure constraints. Despite its rigorously formalized theoretical security, its practical deployment faces side-channel threats, notably Correlation Power Analysis (CPA) attacks. This paper systematically investigates the physical security of its core...

The large key size for fully homomorphic encryption (FHE) requires substantial costs to generate and transmit the keys. This has been problematic for FHE clients who want to delegate the computation, as they often have limited power. A recent work, Lee-Lee-Kim-No [Asiacrypt 2023], partly solved this problem by suggesting a hierarchical key management system. However, the overall key size was still several gigabytes for real-world applications, and it is barely satisfactory for mobile phones...

Succinct Non-Interactive Arguments of Knowledge (SNARKs) provide a powerful cryptographic framework enabling short, quickly verifiable proofs for computational statements. Existing SNARKs primarily target computations represented as arithmetic circuits. However, they become inefficient when handling binary operations, as each gates operates on a few bits while still incurring the cost of multiple field operations per gate. This inefficiency stems, in part, from their inability to capture...

In this paper, we focus on SM4, a widely used and standardized Chinese block cipher. After revisiting the previously proposed optimal 19-round differential characteristic, we observe that its applicability in differential attacks is limited by a reduced pre-sieving probability, causing the time complexity to exceed that of brute force. To overcome this issue, we employ an automated search approach to identify more promising optimal 19-round differential characteristics. By translating key...

Fully Homomorphic Encryption (FHE) presents unique challenges in programming due to the contrast between traditional and FHE language paradigms. A key challenge is selecting ciphertext configurations (CCs) to achieve the desired level of security, performance, and accuracy simultaneously. Finding the design point satisfying the goal is often labor-intensive (probably impossible), for which reason previous works settle down to a reasonable CC that brings acceptable performance. When FHE is...

This document is a preliminary version of what is intended to be submitted to NIST by Zama as part of their threshold call. The document also serves as partial documentation of the protocols used in the Zama MPC system for threshold TFHE. However, note that the Zama software includes many optimizations built on top of the simple specifications given here. In particular the TFHE parameters given here are larger than those used by the Zama software. This is because the Zama TFHE library...

At CRYPTO 2019, Gohr pioneered the integration of differential cryptanalysis with neural networks, demonstrating significant advantages over traditional distinguishers. Subsequently, at Inscrypt 2020, Su et al. proposed the concept of constructing polyhedral differential neural distinguishers by leveraging multiple effective input differences. More recently, at FSE 2024, Bellini et al. introduced a general-purpose tool for automating the training of single-key differential neural...

Safety and liveness are the two classical security properties of consensus protocols. Recent works have strengthened safety with accountability: should any safety violation occur, a sizable fraction of adversary nodes can be proven to be protocol violators. This paper studies to what extent analogous accountability guarantees are achievable for liveness. To reveal the full complexity of this question, we introduce an interpolation between the classical synchronous and partially-synchronous...

In this work, we explore neural network design options for discriminating Random Number Generators(RNG), as a complement to existing statistical test suites, being a continuation of a recent paper of the aothors. Specifically, we consider variations in architecture and data preprocessing. We test their impact on the network's ability to discriminate sequences from a low-quality RNG versus a high-quality one—that is, to discriminate between "optimal" sequence sets and those from the...

Most homomorphic encryption (FHE) schemes exploit a technique called single-instruction multiple-data (SIMD) to process several messages in parallel. However, they base their security in somehow strong assumptions, such as the hardness of approximate lattice problems with superpolynomial approximation factor. On the other extreme of the spectrum, there are lightweight FHE schemes that have much faster bootstrapping but no SIMD capabilities. On the positive side, the security of these schemes...

We revisit the longstanding open problem of implementing Nakamoto's proof-of-work (PoW) consensus based on a real-world computational task $T(x)$ (as opposed to artificial random hashing), in a truly permissionless setting where the miner itself chooses the input $x$. The challenge in designing such a Proof-of-Useful-Work (PoUW) protocol, is using the native computation of $T(x)$ to produce a PoW certificate with prescribed hardness and with negligible computational overhead over the...

Multisignature schemes are crucial for secure operations in digital wallets and escrow services within smart contract platforms, particularly in the emerging post-quantum era. Existing post-quantum multisignature constructions either do not address the stringent requirements of the Quantum Random Oracle Model (QROM) or fail to achieve practical efficiency due to suboptimal parameter choices. In this paper, we present a novel Dilithium-based multisignature scheme designed to be secure in...

Bilinear pairings constitute a cornerstone of public-key cryptography, where advancements in Tate pairings and their efficient variants have emerged as a critical research domain within cryptographic science. Currently, the computation of pairings can be effectively implemented through three distinct algorithmic approaches: Miller’s algorithm, the elliptic net algorithm (as developed by Stange), and cubical-based algorithms (as proposed by Damien Robert). Biextensions are the geometric...

In this paper, we investigate the Extended Gabidulin (EG) codes and the Interleaved EG (IEG) codes, and enhance the Rank Quasi-Cyclic (RQC) encryption scheme. Our primary contribution is the development of a general decoding algorithm for (I)EG codes, for which we precisely provide the DFR, bound the decoding capacity, and estimate the decoding complexity. As the core tool, we demonstrate that the Linear Reconstruction (LR) problem derived from the decoding (I)EG codes problem can be...

Proxy re-encryption (PRE) schemes enable a semi-honest proxy to transform a ciphertext of one user $i$ to another user $j$ while preserving the privacy of the underlying message. Multi-hop PRE schemes allow a legal ciphertext to undergo multiple transformations, but for lattice-based multi-hop PREs, the number of transformations is typically bounded due to the increase of error terms. Recently, Zhao et al. (Esorics 2024) introduced a lattice-based unbounded multi-hop (homomorphic) PRE scheme...

Recently, Dupin and Abelard proposed a broadcast encryption scheme which outperforms the Complete Subtree-based and Subset Difference broadcast encryption in terms of encryption cost and bandwidth requirement. However, Dupin and Abelard acknowledge that the worst-case bound for bandwidth requirement of Complete Subtree approach can be reached in their scheme as well. In this paper, we answer the call to further reduce this bandwidth bottleneck. We first provide concrete analysis to show how...

Asynchronous Complete Secret Sharing (ACSS) is a foundational module for asynchronous networks, playing a critical role in cryptography. It is essential for Asynchronous Secure Multi-Party Computation (AMPC) and, with termination, is widely applied in Validated Asynchronous Byzantine Agreement (VABA) and Asynchronous Distributed Key Generation (ADKG) to support secure distributed systems. Currently, there are relatively few statistical secure ACSS protocols that can guarantee termination,...

In Hamming Quasi-Cyclic (HQC), one of the finalists in the NIST competition for the standardization of post-quantum cryptography, decryption relies on decoding a noisy codeword through a public error-correcting code. The noise vector has a special form that depends on the secret key (a pair of sparse polynomials). However, the decoder, which is currently employed in HQC, is agnostic to the secret key, operating under the assumption that the error arises from a Binary Symmetric Channel (BSC)....

Well-trained deep neural networks (DNN), including large language models (LLM), are valuable intellectual property assets. To defend against model extraction attacks, one of the major ideas proposed in a large body of previous research is obfuscation: splitting the original DNN and storing the components separately. However, systematically analyzing the methods’ security against various attacks and optimizing the efficiency of defenses are still challenging. In this paper, We propose a...

Typical protocols in the multi-party private set operations (MPSO) setting enable $m > 2$ parties to perform certain secure computation on the intersection or union of their private sets, realizing a very limited range of MPSO functionalities. Most works in this field focus on just one or two specific functionalities, resulting in a large variety of isolated schemes and a lack of a unified framework in MPSO research. In this work, we present an MPSO framework, which allows $m$ parties, each...

When Nakamoto invented Bitcoin, the first generation of cryptocurrencies followed it in applying POW (Proof of Work) consensus mechanism; due to its excessive energy consumption and heavy carbon footprints, new innovations evolved like Proof of Space, POS (Proof of Stake), and a lot more with many variants for each. Furthermore, the emergence of more blockchain applications and kinds beyond just cryptocurrencies needed more consensus mechanisms that is optimized to fit requirements of each...

In the McEliece public-key encryption scheme, a private key is almost always not determined uniquely by its associated public key. This paper gives a structural characterization of equivalent private keys, generalizing a result known for the more approachable special case $\lvert L\rvert=q$. These equivalences reduce the cost estimate for a simple private-key search using the support-splitting algorithm (SSA) by a polynomial but practically very substantial factor. We provide an optimized...

Quantum computing is regarded as one of the most significant upcoming advancements in computer science. Although fully operational quantum computers have yet to be realized, they are expected to solve specific problems that are difficult to solve using classical computers. Given the limitations of quantum computing resources, it is crucial to design compact quantum circuits for core operations, such as quantum arithmetic. In this paper, we focus on optimizing the circuit depth of...

This work presents SPHINCSLET, the first fully standard-compliant and area-efficient hardware implementation of the SLH-DSA algorithm, formerly known as SPHINCS+, a post-quantum digital signature scheme. SPHINCSLET is designed to be parameterizable across different security levels and hash functions, offering a balanced trade-off between area efficiency and performance. Existing hardware implementations either feature a large area footprint to achieve fast signing and verification or adopt a...

eIDAS 2.0 (electronic IDentification, Authentication and trust Services) is a very ambitious regulation aimed at equipping European citizens with a personal digital identity wallet (EU Digital Identity Wallet) on a mobile phone that not only needs to achieve a high level of security, but also needs to be available as soon as possible for a large number of citizens and respect their privacy (as per GDPR - General Data Protection Regulation). In this paper, we introduce the foundations of...

A Random Oracle Combiner (ROC), introduced by Dodis et al. (CRYPTO ’22), takes two hash functions $h_1, h_2$ from m bits to n bits and outputs a new hash function $C$ from $m$' to $n$' bits. This function C is guaranteed to be indifferentiable from a fresh random oracle as long as one of $h_1$ and $h_2$ (say, $h_1$) is a random oracle, while the other h2 can “arbitrarily depend” on $h_1$. The work of Dodis et al. also built the first length-preserving ROC, where $n$′ = $n$. Unfortunately,...

Laconic cryptography focuses on designing two-message protocols that allow secure computation on large datasets while minimizing communication costs. While laconic cryptography protocols achieve asymptotically optimal communication complexity for many tasks, their concrete efficiency is prohibitively expensive due to the heavy use of public-key techniques or the non-black-box of cryptographic primitives. In this work, we initiate the study of "laconic cryptography with preprocessing",...

In this paper, we present efficient SNARKs for Boolean circuits, achieving significant improvements in the prover efficiency. The core of our technique is a novel tower sumcheck protocol and a tower zero-check protocol tailored for tower fields, which enable this efficiency boost. When instantiated with Wiedemann's binary tower fields with the base field of $GF(2)$ and the top-level field $GF(2^{2^\ell})$, assuming the quadratic complexity of multiplications \(O(2^{2\ell})\) in the top-level...

Zero-knowledge proofs (ZKPs) are cryptographic protocols that enable a prover to convince a verifier of a statement's truth without revealing any details beyond its validity. Typically, the statement is encoded as an arithmetic circuit, and allows the prover to demonstrate that the circuit evaluates to true without revealing its inputs. Despite their potential to enhance privacy and security, ZKPs are difficult to write and optimize, limiting their adoption in machine learning and data...

We demonstrate an attack on the soundness of a widely known optimization of the Gemini multilinear Polynomial Commitment Scheme (PCS). The attack allows a malicious prover to falsely claim that a multilinear polynomial takes a value of their choice, for any input point. We stress that the original Gemini multilinear PCS and HyperKZG, an adaptation of Gemini, are not affected by the attack.

Since the selection of the National Institute of Standards and Technology (NIST) Post-Quantum Cryptography (PQC) standardization algorithms, research on integrating PQC into security protocols such as TLS/SSL, IPSec, and DNSSEC has been actively pursued. However, PQC migration for Internet of Things (IoT) communication protocols remains largely unexplored. Embedded devices in IoT environments have limited computational power and memory, making it crucial to optimize PQC algorithms for...

Distributed SNARKs enable multiple provers to collaboratively generate proofs, enhancing the efficiency and scalability of large-scale computations. The state-of-the-art distributed SNARK for Plonk, Pianist (S\&P '24), achieves constant proof size, constant amortized communication complexity, and constant verifier complexity. However, when proving the Rank-One Constraint System (R1CS), a widely used intermediate representation for SNARKs, Pianist must perform the transformation from R1CS...

Hardware IP blocks have been subjected to various forms of confidentiality and integrity attacks in recent years due to the globalization of the semiconductor industry. System-on-chip (SoC) designers are now considering a zero-trust model for security, where an IP can be attacked at any stage of the manufacturing process for piracy, cloning, overproduction, or malicious alterations. Hardware redaction has emerged as a promising countermeasure to thwart confidentiality and integrity attacks...

This work presents an exact and compact formula for the probability of rotation-xor differentials (RX-differentials) through modular addition, for arbitrary rotation amounts, which has been a long-standing open problem. The formula comes with a rigorous proof and is also verified by extensive experiments. Our formula uncovers error in a recent work from 2022 proposing a formula for rotation amounts bigger than 1. Surprisingly, it also affects correctness of the more studied and used...

In recent years, the integration of deep learning with differential cryptanalysis has led to differential neural cryptanalysis, enabling efficient data-driven security evaluation of modern cryptographic algorithms. Compared to traditional differential cryptanalysis, differential neural cryptanalysis enhances the efficiency and automation of the analysis by training neural networks to automatically extract statistical features from ciphertext pairs. As research advances, neural distinguisher...

As artificial intelligence (AI) becomes increasingly embedded in high-stakes applications such as healthcare, finance, and autonomous systems, ensuring the verifiability of AI computations without compromising sensitive data or proprietary models is crucial. Zero-knowledge machine learning (ZKML) leverages zero-knowledge proofs (ZKPs) to enable the verification of AI model outputs while preserving confidentiality. However, existing ZKML approaches require specialized cryptographic expertise,...

Zero-knowledge range arguments are a fundamental cryptographic primitive that allows a prover to convince a verifier of the knowledge of a secret value lying within a predefined range. They have been utilized in diverse applications, such as confidential transactions, proofs of solvency and anonymous credentials. Range arguments with a transparent setup dispense with any trusted setup to eliminate security backdoor and enhance transparency. They are increasingly deployed in diverse...

Efficiently protecting embedded software implementations of standard symmetric cryptographic primitives against side-channel attacks has been shown to be a considerable challenge in practice. This is, in part, due to the most natural countermeasure for such ciphers, namely Boolean masking, not amplifying security well in the absence of sufficient physical noise in the measurements. So-called prime-field masking has been demonstrated to provide improved theoretical guarantees in this context,...

A secret-sharing scheme is a method by which a dealer distributes shares to parties such that only authorized subsets of parties can reconstruct the secret. Secret-sharing schemes are an important tool in cryptography and they are used as a building block in many secure protocols, e.g., secure multiparty computation protocols for arbitrary functionalities, Byzantine agreement, threshold cryptography, access control, attribute-based encryption, and weighted cryptography (e.g., stake-based...

Sigma protocols ($\Sigma$-protocols) provide a foundational paradigm for constructing secure algorithms in privacy-preserving applications. To enhance efficiency, several extended models [BG18], [BBB+18], [AC20] incorporating various optimization techniques have been proposed as ``replacements'' for the original $\Sigma$-protocol. However, these models often lack the expressiveness needed to handle complex relations and hinder designers from applying appropriate instantiation and...

The Advanced Encryption Standard (AES) in Galois/Counter Mode (GCM) delivers both confidentiality and integrity yet poses performance and security challenges on resource-limited microcontrollers. In this paper, we present an optimized AES-GCM implementation for the ARM Cortex-M4 that combines Fixslicing AES with the FACE (Fast AES-CTR Encryption) strategy, significantly reducing redundant computations in AES-CTR. We further examine two GHASH implementations—a 4-bit Table-based approach and a...

We present almost-optimal lattice-based attribute-based encryption (ABE) and laconic function evaluation (LFE). For depth d circuits over $\ell$-bit inputs, we obtain * key-policy (KP) and ciphertext-policy (CP) ABE schemes with ciphertext, secret key and public key size $O(1)$; * LFE with ciphertext size $\ell + O(1)$ as well as CRS and digest size $O(1)$; where O(·) hides poly(d, λ) factors. The parameter sizes are optimal, up to the poly(d) dependencies. The security of our...

This work introduce a new approach called Max bias analysis for the entropy computation of structures of Free Ring Oscillator-based Physical Random Number Generator. It employs the stochastic model based on the well-established Wiener process, specifically adapted to only capture thermal noise contributions while accounting for potential non-zero bias in the duty cycle. Our analysis is versatile, applicable to combinations of multiple sampled Ring Oscillator (RO) filtering by any function....

DNA edit distance (ED) measures the minimum number of single nucleotide insertions, substitutions, or deletions required to convert a DNA sequence into another. ED has broad applications in healthcare such as sequence alignment, genome assembly, functional annotation, and drug discovery. Privacy-preserving computation is essential in this context to protect sensitive genomic data. Nonetheless, the existing secure DNA edit distance solutions lack efficiency when handling large data sequences...

Side-channel analysis (SCA) is a growing field in hardware security where adversaries extract secret information from embedded devices by measuring physical observables like power consumption and electromagnetic emanation. SCA is a security assessment method used by governmental labs, standardization bodies, and researchers, where testing is not just limited to standardized cryptographic circuits, but it is expanded to AI accelerators, Post Quantum circuits, systems, etc. Despite its...

In this paper we provide new theoretical and empirical evidences that gradient-based deep learning profiling attacks (DL-SCA) suffer from masking schemes. This occurs through an initial stall of the learning process: the so-called plateau effect. To understand why, we derive an analytical expression of a DL-SCA model targeting simulated traces which enables us to study an analytical expression of the loss. By studying the loss landscape of this model, we show that not only do the magnitudes...

Scloud+ is an unstructured LWE-based key encapsulation mechanism (KEM) with conservative quantum security, in which ternary secrets and lattice coding are incorporated for higher computational and communication efficiency. However, its efficiencies are still much inferior to those of the structured LWE-based KEM, like ML-KEM (standardized by NIST). In this paper, we present a configurable hardware architecture for Scloud+.KEM to improve the computational efficiency. Many algorithmic and...

Recently, Differential Fault Attacks (DFAs) have proven highly effective against stream ciphers designed for Hybrid Homomorphic Encryption (HHE). In this work, we present a table-based DFA framework called the \textit{shortcut attack}, which generalizes the attack proposed by Wang and Tang on the cipher \textsf{Elisabeth}. The framework applies to a broad sub-family of ciphers following the Group Filter Permutator (GFP) paradigm and enhances previous DFAs by improving both the fault...

Hyperledger Fabric is a unique permissioned platform for implementing blockchain in a consortium. It has a distinct transaction flow of execute-order-validate. During the execution phase, a pre-determined set of endorsing peers execute a transaction and sign the transaction response. This process is termed endorsement. In the validation phase, peers validate the transaction with reference to an endorsement policy. The identity of the endorsing organizations is obtainable to all the nodes in...

We revisit the problem of secure aggregation of high-dimensional vectors in a two-server system such as Prio. These systems are typically used to aggregate vectors such as gradients in private federated learning, where the aggregate itself is protected via noise addition to ensure differential privacy. Existing approaches require communication scaling with the dimensionality, and thus limit the dimensionality of vectors one can efficiently process in this setup. We propose PREAMBLE:...

The most fundamental performance metrics of secure multi-party computation (MPC) protocols are related to the number of messages the parties exchange (i.e., round complexity), the size of these messages (i.e., communication complexity), and the overall computational resources required to execute the protocol (i.e., computational complexity). Another quality metric of MPC protocols is related to the black-box or non-black-box use of the underlying cryptographic primitives. Indeed, the design...

The rapid growth of cloud computing and data-driven applications has amplified privacy concerns, driven by the increasing demand to process sensitive data securely. Homomorphic encryption (HE) has become a vital solution for addressing these concerns by enabling computations on encrypted data without revealing its contents. This paper provides a comprehensive evaluation of two leading HE libraries, SEAL and OpenFHE, examining their performance, usability, and support for prominent HE schemes...

Efficient implementation of a pairing-based cryptosystem relies on high-performance arithmetic in finite fields $\mathbb{F}_{p}$ and their extensions $\mathbb{F}_{p^k}$, where $k$ is the embedding degree. A small embedding degree is crucial because part of the arithmetic for pairing computation occurs in $\mathbb{F}_{{p}^k}$ and includes operations such as squaring, multiplication, and Frobenius operations. In this paper, we present a fast and efficient method for computing the Frobenius...

Poly1305 is a widely-deployed polynomial hash function. The rationale behind its design was laid out in a series of papers by Bernstein, the last of which dates back to 2005. As computer architectures evolved, some of its design features became less relevant, but implementers found new ways of exploiting these features to boost its performance. However, would we still converge to this same design if we started afresh with today's computer architectures and applications? To answer this...

The key collision attack was proposed as an open problem in key-committing security in Authenticated Encryption (AE) schemes like $\texttt{AES-GCM}$ and $\texttt{ChaCha20Poly1305}$. In ASIACRYPT 2024, Taiyama et al. introduce a novel type of key collision—target-plaintext key collision ($\texttt{TPKC}$) for $\texttt{AES}$. Depending on whether the plaintext is fixed, $\texttt{TPKC}$ can be divided into $\texttt{fixed-TPKC}$ and $\texttt{free-TPKC}$, which can be directly converted into...

Privacy-preserving distributed computation enables a resource-limited client to securely delegate computations on sensitive data to multiple servers by distributing shares of the data. In such systems, verifiable secret sharing (VSS) is a fundamental component, ensuring secure data distribution and directly impacting the overall performance. The most practical approach to construct VSS is through polynomial commitment (PC), with two main research directions to improve the VSS efficiency....

Oblivious permutation (OP) enables two parties, a sender with a private data vector $x$ and a receiver with a private permutation π, to securely obtain the shares of π(x). OP has been used to construct many important MPC primitives and applications such as secret shuffle, oblivious sorting, private set operations, secure database analysis, and privacy-preserving machine learning. Due to its high complexity, OP has become a performance bottleneck in several practical applications, and many...

Matrix multiplication of two encrypted matrices (CC-MM) is a key challenge for privacy-preserving machine learning applications. As modern machine learning models focus on scalability, fast CC-MM on large datasets is increasingly in demand. In this work, we present a CC-MM algorithm for large matrices. The algorithm consists of plaintext matrix multiplications (PP-MM) and ciphertext matrix transpose algorithms (C-MT). We propose a fast C-MT algorithm, which is computationally inexpensive...

In verifiable secret sharing (VSS), a dealer shares a secret input among several parties, ensuring each share is verifiable. Motivated by its applications in the blockchain space, we focus on a VSS where parties holding shares are not allowed to reconstruct the dealer's secret (even partially) on their own terms, which we address as privacy-targeted collusion if attempted. In this context, our work investigates mechanisms deterring such collusion in VSS among rational and malicious...

In this paper, we study preimage resistance of the SHA-3 standard. We propose a squeeze meet-in-the-middle attack as a new preimage attack method for the sponge functions. This attack combines the squeeze attack and meet-in-the-middle attack, and is implemented by internal differentials. We analyze the inverse operation of the SHA-3 round function, and develop a new target internal differential algorithm as well as a linearization technique for the Sbox in the backward phase. In addition, we...

Non-malleable zero-knowledge (NMZK), originally introduced in the seminal work of Dolev, Dwork, and Naor (STOC 91), is a fundamental concept for modeling the security of proof systems against man-in-the-middle attacks. Recently, Kim, Liang, and Pandey (CRYPTO 2022) presented the first efficient constant-round NMZK argument system based solely on symmetric-key cryptography. Their construction relies on a non-black-box use of the involved cryptographic primitives and on multiple...

Bootstrapping in approximate homomorphic encryption involves evaluating the modular reduction function. Traditional methods decompose the modular reduction function into three components: scaled cosine, double-angle formula, and inverse sine. While these approaches offer a strong trade-off between computational cost and level consumption, they lack flexibility in parameterization. In this work, we propose a new method to decompose the modular reduction function with improved...

Secure Two-Party Computation (2PC) enables secure inference with cryptographic guarantees that protect the privacy of the model owner and client. However, it adds significant performance overhead. In this work, we make 2PC-based secure inference efficient while considering important deployment scenarios. We observe that the hitherto unconsidered latency of fetching keys from storage significantly impacts performance, as does network speed. We design a Linear Secret Sharing (LSS)-based...

Consider a weak analyst that wishes to outsource data collection and computation of aggregate statistics over a a potentially large population of (also weak) clients to a powerful server. For flexibility and efficiency, we consider public-key and non-interactive protocols, meaning the clients know the analyst's public key but do not share secrets, and each client sends at most one message. Furthermore, the final step should be silent, whereby the analyst simply downloads the (encrypted)...

Deimos Cipher is a symmetric encryption algorithm designed to achieve high entropy, strong diffusion, and computational efficiency. It integrates HKDF with BLAKE2b for key expansion, ensuring secure key derivation from user-supplied passwords. The encryption process employs XChaCha20, a high-speed stream cipher, to provide strong security and resistance against nonce reuse attacks. To guarantee data integrity and authentication, HMAC-SHA256 is used, preventing unauthorized...

The introduction of shared computation architectures assembled from heterogeneous chiplets introduces new security threats. Due to the shared logical and physical resources, an untrusted chiplet can act maliciously to surreptitiously probe the data communication between chiplets or sense the computation shared between them. This paper presents Garblet, the first framework to leverage the flexibility offered by chiplet technology and Garbled Circuits (GC)-based MPC to enable efficient,...

Decentralization is a great enabler for adoption of modern cryptography in real-world systems. Widespread adoption of blockchains and secure multi-party computation protocols are perfect evidentiary examples for dramatic rise in deployment of decentralized cryptographic systems. Much of cryptographic research can be viewed as reducing (or eliminating) the dependence on trusted parties, while shielding from stronger adversarial threats. In this work, we study the problem of multi-authority...

S-boxes are the most popular nonlinear building blocks used in symmetric-key primitives. Both cryptographic properties and implementation cost of an S-box are crucial for a good cipher design, especially for lightweight ones. This paper aims to determine the exact minimum area of optimal 4-bit S-boxes (whose differential uniform and linearity are both 4) under certain standard cell library. Firstly, we evaluate the upper and lower bounds upon the minimum area of S-boxes, by...

In pairing-based cryptography, the final exponentiation with a large fixed exponent is crucial for ensuring unique outputs in both Tate and optimal ate pairings. While significant strides have been made in optimizing elliptic curves with even embedding degrees, progress remains limited for curves with odd embedding degrees, especially those divisible by $3$. This paper introduces novel techniques to optimize the computation of the final exponentiation for the optimal ate pairing on such...

Lee et al. proposed a new bootstrapping algorithm based on homomorphic automorphism, which merges the empty sets of ciphertexts by adjusting the window size. This algorithm supports arbitrary secret key distributions with no additional runtime costs while using small evaluation keys. However, our implementation reveals that once the window size exceeds a certain threshold, the time required for bootstrapping remains relatively constant. This observation prompts the question of how to further...

This paper addresses the critical challenges in designing cryptographic algorithms that achieve both high performance and cross-platform efficiency on ARM and x86 architectures, catering to the demanding requirements of next-generation communication systems, such as 6G and GPU/NPU interconnections. We propose HiAE, a high-throughput authenticated encryption algorithm optimized for performance exceeding 100 Gbps and designed to meet the stringent security requirements of future communication...

We initiate the study of {\em split prover zkSNARKs}, which allow Alice to offload part of the zkSNARK computation to her assistant, Bob. In scenarios like online transactions (e.g., zCash), a significant portion of the witness (e.g., membership proofs of input coins) is often available to the prover (Alice) before the transaction begins. This setup offers an opportunity to Alice to initiate the proof computation early, even before the entire witness is available. The remaining computation...

Secure two-party comparison, known as Yao's millionaires' problem, has been a fundamental challenge in privacy-preserving computation. It enables two parties to compare their inputs without revealing the exact values of those inputs or relying on any trusted third party. One elegant approach to secure computation is based on homomorphic encryption. Recently, building on this approach, Carlton et al. (CT-RSA 2018) and Bourse et al. (CT-RSA 2020) presented novel solutions for the problem of...

In a secret sharing scheme with polynomial sharing, the secret is an element of a finite field, and the shares are obtained by evaluating polynomials on the secret and some random field elements, i.e., for every party there is a set of polynomials that computes the share of the party. These schemes generalize the linear ones, adding more expressivity and giving room for more efficient schemes. To identify the access structures for which this efficiency gain is relevant, we need a systematic...

Highly-optimized assembly is commonly used to achieve the best performance for popular cryptographic schemes such as the newly standardized ML-KEM and ML-DSA. The majority of implementations today rely on hand-optimized assembly for the core building blocks to achieve both security and performance. However, recent work by Abdulrahman et al. takes a new approach, writing a readable base assembly implementation first and leaving the bulk of the optimization work to a tool named SLOTHY based...

In this work, we explore the field of lattice-based Predicate Encryption (PE), with a focus on enhancing compactness and refining functionality. First, we present a more compact bounded collusion predicate encryption scheme compared to previous constructions, significantly reducing both the per-unit expansion and fixed overhead, while maintaining an optimal linear blow-up proportional to $Q$. Next, we propose a Predicate Inner Product Functional Encryption (P-IPFE) scheme based on our...

In this work, we consider the setting where the process of securely evaluating a multi-party functionality is divided into two phases: offline (or preprocessing) and online. The offline phase is independent of the parties’ inputs, whereas the online phase does require the knowledge of the inputs. We consider the problem of minimizing the round of communication required in the online phase and propose a round preserving compiler that can turn a big class of multi-party computation (MPC)...

With the growing emphasis on data privacy, secure multi-party computation has garnered significant attention for its strong security guarantees in developing privacy-preserving machine learning (PPML) schemes. However, only a few works address scenarios with a large number of participants. The state of the art by Liu et al. (LXY24, USENIX Security'24) first achieves a practical PPML protocol for up to 63 parties but is constrained to semi-honest security. Although naive extensions to the...

We propose the notion of succinct oblivious tensor evaluation (OTE), where two parties compute an additive secret sharing of a tensor product of two vectors $\mathbf{x} \otimes \mathbf{y}$, exchanging two simultaneous messages. Crucially, the size of both messages and of the CRS is independent of the dimension of $\mathbf{x}$. We present a construction of OTE with optimal complexity from the standard learning with errors (LWE) problem. Then we show how this new technical tool enables a...

In Crypto'19, Goyal, Jain, and Sahai (GJS) introduced the elegant notion of *secret-sharing of an NP statement* (NPSS). Roughly speaking, a $t$-out-of-$n$ secret sharing of an NP statement is a reduction that maps an instance-witness pair to $n$ instance-witness pairs such that any subset of $(t-1)$ reveals no information about the original witness, while any subset of $t$ allows full recovery of the original witness. Although the notion was formulated for general $t \leq n$, the only...

A Garbling Scheme is a fundamental cryptographic primitive, with numerous theoretical and practical applications. Since its inception by Yao (FOCS'82, '86), optimizing the communication and computation complexities of securely garbling circuits has been an area of active research. One such optimization, and perhaps the most fundamental, is the `Free-XOR' technique (Kolesnikov and Schneider, ICALP'08) which allows XOR gates in a function garbling to not require representation, and therefore...

This paper presents a novel single-trace side-channel attack on FALCON—a lattice-based post-quantum digital signature protocol recently approved for standardization by NIST. We target the discrete Gaussian sampling operation within the FALCON key generation scheme and use a single power measurement trace to succeed. Notably, negating the ‘shift right 63-bit’ operation (for 64-bit values) leaks critical information about the ‘-1’ vs. ‘0’ assignments to intermediate coefficients. These leaks...

SCARF is a tweakable block cipher dedicated to cache address randomization, proposed at the USENIX Security conference. It has a 10-bit block, 48-bit tweak, and 240-bit key. SCARF is aggressively optimized to meet the harsh latency constraints of cache address randomization, and uses a dedicated model for its security claim. The full version of SCARF has 8 rounds, and its designers claim security up to $2^{40}$ queries and $2^{80}$ computations. In this work we present a distinguisher...

The public comments received for the review process for NIST (SP) 800-38A pointed out two important issues that most companies face: (1) the limited security that AES can provide due to its 128-bit block size and (2) the problem of nonce-misuse in practice. In this paper, we provide an alternative solution to these problems by introducing two optimally secure deterministic authenticated encryption (DAE) schemes, denoted as DENC1 and DENC2 respectively. We show that our proposed constructions...

The celebrated Algorand protocol solves validated byzantine agreement in a scalable manner in the synchronous setting. In this paper, we study the feasibility of similar solutions in the asynchronous setting. Our main result is an asynchronous validated byzantine agreement protocol that we call Asynchronous Algorand. As with Algorand, it terminates in an expected constant number of rounds, and honest parties send an expected $O(n ~\mathsf{polylog}~n)$ bits, where $n$ is the number of...

The U.S. National Institute of Standards and Technology recently standardized the first set of post-quantum cryptography algo- rithms. These algorithms address the quantum threat, but also present new challenges due to their larger memory and computational footprint. Three of the four standardized algorithms are lattice based, offering good performance but posing challenges due to complex implementation and intricate security assumptions. A more conservative choice for quantum- safe...