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...

Verifiable computation over encrypted data is gaining increasing attention, and using SNARKs to provide proofs for FHE operations has emerged as a promising approach. However, the mismatch between FHE's typically small prime fields and SNARKs' larger field requirements creates verifiable FHE challenges. In this work, we construct a packed sumcheck algorithm specifically designed for small fields. This approach leverages folding and repetition techniques to maintain security without field...

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...

Searchable encryption (SE) enables privacy-preserving keyword search on encrypted data. Public-key SE (PKSE) supports multi-user searches but suffers from high search latency due to expensive public-key operations. Symmetric SE (SSE) offers a sublinear search but is mainly limited to single-user settings. Recently, hybrid SE (HSE) has combined SSE and PKSE to achieve the best of both worlds, including multi-writer encrypted search functionalities, forward privacy, and sublinear search with...

Constructing and implementing isogeny-based cryptographic primitives is an active research. In particular, performing length-$n$ isogenies walks over quadratic field extensions of $\mathbb{F}_p$ plays an exciting role in some constructions, including Hash functions, Verifiable Delay Functions, Key-Encapsulation Mechanisms, and generic proof systems for isogeny knowledge. Remarkably, many isogeny-based constructions, for efficiency, perform $2$-isogenies through square root...

As billions of people rely on end-to-end encrypted messaging, the exposure of metadata, such as communication timing and participant relationships, continues to deanonymize users. Asynchronous metadata-hiding solutions with strong cryptographic guarantees have historically been bottlenecked by quadratic $O(N^2)$ server computation in the number of users $N$ due to reliance on private information retrieval (PIR). We present Myco, a metadata-private messaging system that preserves strong...

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 show that Montgomery ladders compute pairings as a by-product, and explain how a small adjustment to the ladder results in simple and efficient algorithms for the Weil and Tate pairing on elliptic curves using cubical arithmetic. We demonstrate the efficiency of the resulting cubical pairings in several applications from isogeny-based cryptography. Cubical pairings are simpler and more performant than pairings computed using Miller's algorithm: we get a speed-up of over 40% for use-cases...

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...

Fully Homomorphic Encryption (FHE) enables computation on encrypted data without decryption, demonstrating significant potential for privacy-preserving applications. However, FHE faces several challenges, one of which is the significant plaintext-to-ciphertext expansion ratio, resulting in high communication overhead between client and server. The transciphering technique can effectively address this problem by first encrypting data with a space-efficient symmetric cipher, then converting...

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...

Generalized secret sharing (GSS) enables flexible access control in distributed systems by allowing secrets to be shared across arbitrary monotone access structures. However, its adoption in transparent and trustless environments is hindered due to the reliance on trusted participants and secure communication channels. This reliance restricts GSS's ability to provide flexible control in the presence of adversaries. In this paper, we propose publicly verifiable generalized secret sharing...

Mixnets are powerful building blocks for providing anonymity in applications like electronic voting and anonymous messaging. The en- cryption schemes upon which traditional mixnets are built, as well as the zero-knowledge proofs used to provide verifiability, will, however, soon become insecure once a cryptographically-relevant quantum computer is built. In this work, we construct the most compact verifiable mixnet that achieves privacy and verifiability through encryption and...

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...

As real-world networks such as social networks and computer networks are often complex and distributed, modeling them as multilayer graphs is gaining popularity. For instance, when studying social interactions across platforms like LinkedIn, Facebook, TikTok, and Bluesky, users may be connected on several of these platforms. To identify important nodes/users, the platforms might wish to analyze user interactions using, e.g., centrality measures when accounting for connections across all...

The scalability of modern decentralized blockchain systems is constrained by the requirement that the participating nodes execute the entire chains transactions without the ability to delegate the verification workload across multiple actors trustlessly. This is further limited by the need for sequential transaction execution and repeated block validation, where each node must re-execute all transactions before accepting blocks, also leading to delayed broadcasting in many...

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...

The YOSO (You Only Speak Once) model, introduced by Gentry et al. (CRYPTO 2021), helps to achieve strong security guarantees in cryptographic protocols for distributed settings, like blockchains, with large number of parties. YOSO protocols typically employ smaller anonymous committees to execute individual rounds of the protocol instead of having all parties execute the entire protocol. After completing their tasks, parties encrypt protocol messages for the next anonymous committee and...

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...

Modern life makes having a digital identity no longer optional, whether one needs to manage a bank account or subscribe to a newspaper. As the number of online services increases, it is fundamental to safeguard user privacy and equip service providers (SP) with mechanisms enforcing Sybil resistance, i.e., preventing a single entity from showing as many. Current approaches, such as anonymous credentials and self-sovereign identities, typically rely on identity providers or identity...

Secure two-party computation (2PC) enables two parties to jointly evaluate a function while maintaining input privacy. Despite recent significant progress, a notable efficiency gap remains between actively secure and passively secure protocols. In S\&P'12, Huang, Katz, and Evans formalized the notion of \emph{active security with one-bit leakage}, providing a promising approach to bridging this gap. Protocols derived from this notion have become foundational in designing highly efficient...

Semantic communication systems, which focus on transmitting the semantics of data rather than its exact reconstruction, redefine the design of communication networks for transformative efficiency in bandwidth-limited and latency-critical applications. Addressing these goals, we tackle the rate-distortion-perception (RDP) problem for image compression, a critical challenge in achieving perceptually realistic reconstructions under rate constraints. Formulated within the randomized distributed...

CRLite is a low-bandwidth, low-latency, privacy-preserving mechanism for distributing certificate revocation data. A CRLite aggregator periodically encodes revocation data into a compact static hash set, or membership test, which can can be downloaded by clients and queried privately. We present a novel data-structure for membership tests, which we call a clubcard, and we evaluate the encoding efficiency of clubcards using data from Mozilla's CRLite infrastructure. As of November 2024,...

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...

An oblivious RAM (ORAM) compiler is a cryptographic tool that transforms a program $P$ running in time $n$ into an equivalent program $\tilde P$, with the property that the sequence of memory addresses read from/written to by $\tilde P$ reveal nothing about $\tilde P$'s data (Goldreich and Ostrovsky, JACM'96). An efficient ORAM compiler $C$ should achieve some combination of the following: - Low bandwidth blow-up: $\tilde P$ should read/write a similar amount of data as does P. - Low...

Secure graph computation enables computing on graphs while hiding the graph topology as well as the associated node/edge data. This facilitates collaborative analysis among multiple data owners, who may only hold a private partial view of the global graph. Several works address this problem using the technique of secure multiparty computation (MPC) in the presence of 2 or 3 parties. However, when moving to the multiparty setting, as required for collaborative analysis among multiple data...

The Ethereum Global Network (EGN) is the peer-to-peer (P2P) network underlying Ethereum and thousands of subsequent blockchain services. Deviating from traditional single-service P2P networks, EGN's multi-service architecture has gained widespread acceptance for supposedly improving node discovery efficiency and security. This paper challenges this belief by critically examining EGN's design and its purported benefits. Our analysis reveals significant shortcomings in EGN's node discovery...

The GCM authenticated encryption (AE) scheme is one of the most widely used AE schemes in the world, while it suffers from risk of nonce misuse, short message length per encryption and an insufficient level of security. The goal of this paper is to design new AE schemes achieving stronger provable security in the standard model and accepting longer nonces (or providing nonce misuse resistance), with the design rationale behind GCM. As a result, we propose two enhanced variants of GCM and...

Conventional Publicly Verifiable Secret Sharing (PVSS) protocols allow a dealer to share a secret among $n$ parties without interaction, ensuring that any $t + 1$ parties (where $t+1 \le n$) can recover the secret, while anyone can publicly verify the validity of both the individual shares and the reconstructed secret. PVSS schemes are shown to be a key tool in a wide range of practical applications. In this paper, we introduce Pre-constructed PVSS (PPVSS), an extension of standard PVSS...

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...

Current DAG-based BFT protocols face a critical trade-off: certified DAGs provide strong security guarantees but require additional rounds of communication to progress the DAG construction, while uncertified DAGs achieve lower latency at the cost of either reduced resistance to adversarial behaviour or higher communication costs. This paper presents Starfish, a partially synchronous DAG-based BFT protocol that achieves the security properties of certified DAGs, the efficiency of...

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...

HuFu is an unstructured lattice-based signature scheme proposed during the NIST PQC standardization process. In this work, we present a side-channel analysis of HuFu's reference implementation. We first exploit the multiplications involving its two main secret matrices, recovering approximately half of their entries through a non-profiled power analysis with a few hundred traces. Using these coefficients, we reduce the dimension of the underlying LWE problem, enabling full secret key...

The current landscape of system-on-chips (SoCs) security verification faces challenges due to manual, labor-intensive, and inflexible methodologies. These issues limit the scalability and effectiveness of security protocols, making bug detection at the Register-Transfer Level (RTL) difficult. This paper proposes a new framework named BugWhisperer that utilizes a specialized, fine-tuned Large Language Model (LLM) to address these challenges. By enhancing the LLM's hardware security knowledge...

CHide is one of the most prominent e-voting protocols, which, while combining security and efficiency, suffers from having very long encrypted credentials. In this paper, starting from CHide, we propose a new protocol, based on multiparty Class Group Encryption (CGE) instead of discrete logarithm cryptography over known order groups, achieving a computational complexity of $O(nr)$, for $n$ votes and $r$ voters, and using a single MixNet. The homomorphic properties of CGE allow for more...

Over two decades since their introduction in 2005, all major verifiable pairing delegation protocols for public inputs have been designed to ensure information-theoretic security. However, we note that a delegation protocol involving only ephemeral secret keys in the public view can achieve everlasting security, provided the server is unable to produce a pairing forgery within the protocol’s execution time. Thus, computationally bounding the adversary’s capabilities during the protocol’s...

Blockchain advancements, currency digitalization, and declining cash usage have fueled global interest in Central Bank Digital Currencies (CBDCs). The BIS states that the hybrid model, where central banks authorize intermediaries to manage distribution, is more suitable than the direct model. However, designing a CBDC for practical implementation requires careful consideration. First, the public blockchain raises privacy concerns due to transparency. While zk-SNARKs can be a solution, they...

Digital signatures underpin identity, authenticity, and trust in modern computer systems. Cryptography research has shown that it is possible to prove possession of a valid message and signature for some public key, without revealing the message or signature. These proofs of possession work only for specially-designed signature schemes. Though these proofs of possession have many useful applications to improving security, privacy, and anonymity, they are not currently usable for widely...

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,...

Recent advances in Vector Oblivious Linear Evaluation (VOLE) protocols have enabled constant-round, fast, and scalable (designated-verifier) zero-knowledge proofs, significantly reducing prover computational cost. Existing protocols, such as QuickSilver [CCS’21] and LPZKv2 [CCS’22], achieve efficiency with prover costs of 4 multiplications in the extension field per AND gate for Boolean circuits, with one multiplication requiring a O(κ log κ)-bit operation where κ = 128 is the security...

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...

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...

Single Sign-On (SSO) is a popular authentication mechanism enabling users to access multiple web services with a single set of credentials. Despite its convenience, SSO faces outstanding privacy challenges. The Identity Provider (IdP) represents a single point of failure and can track users across different Relying Parties (RPs). Multiple colluding RPs may track users through common identity attributes. In response, anonymous credential-based SSO solutions have emerged to offer...

Zero-knowledge (ZK) proofs have been recently explored for the integrity of machine learning (ML) inference. However, these protocols suffer from high computational overhead, with the primary bottleneck stemming from the evaluation of non-linear functions. In this paper, we propose the first systematic ZK proof framework for non-linear mathematical functions in ML using the perspective of table lookup. The key challenge is that table lookup cannot be directly applied to non-linear functions...

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...

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...

The Chou-Orlandi batch oblivious transfer (OT) protocol is a particularly attractive OT protocol that bridges the gap between practical efficiency and strong security guarantees and is especially notable due to its simplicity. The security analysis provided by Chou and Orlandi bases the security of their protocol on the hardness of the computational Diffie-Hellman ($\mathsf{CDH}$) problem in prime-order groups. Concretely, in groups in which no better-than-generic algorithms are known for...

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...

The emergence of video streams as a primary medium for communication and the demand for high-quality video sharing over the internet have given rise to several security and privacy issues, such as unauthorized access and data breaches. To address these limitations, various Selective Video Encryption (SVE) schemes have been proposed, which encrypt specific portions of a video while leaving others unencrypted. The SVE approach balances security and usability, granting unauthorized users access...

McEliece cryptosystems, based on code-based cryptography, is a candidate in Round 4 of NIST's post-quantum cryptography standardization process. The QC-MDPC (quasi-cyclic moderate-density parity-check) variant is particularly noteworthy due to its small key length. The Guo-Johansson-Stankovski (GJS) attack against the QC-MDPC McEliece cryptosystem was recently proposed and has intensively been studied. This attack reconstructs the secret key using information on decoding error rate (DER)....

A sequential aggregate signature scheme (SAS) allows multiple potential signers to sequentially aggregate their respective signatures into a single compact signature. Typically, verification of a SAS signatures requires access to all messages and public key pairs utilized in the aggregate generation. However, efficiency is crucial for cryptographic protocols to facilitate their practical implementation. To this end, we propose a sequential aggregate signature scheme with lazy verification...

Key Exchange mechanisms (KE or KEMs) such as the Diffie-Hellman protocol have proved to be a cornerstone conciliating the efficiency of symmetric encryption and the practicality of public key primitives. Such designs however assume the non-compromission of the long term asymmetric key in use. To relax this strong security assumption, and allow for modern security features such as Perfect Forward Secrecy (PFS) or Post Compromise Security (PCS), Ratcheted-KE (RKE) have been proposed. ...

Shor's and Grover's algorithms' efficiency and the advancement of quantum computers imply that the cryptography used until now to protect one's privacy is potentially vulnerable to retrospective decryption, also known as harvest now, decrypt later attack in the near future. This dissertation proposes an overview of the cryptographic schemes used by Tor, highlighting the non-quantum-resistant ones and introducing theoretical performance assessment methods of a local Tor network. The...

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...

This study explores the algebraic cryptanalysis of small-scale variants of the E0 stream cipher, a legacy cipher used in the Bluetooth protocol. By systematically reducing the size of the linear feedback shift registers (LFSRs) while preserving the cipher’s core structure, we investigate the relationship between the number of unknowns and the number of consecutive keystream bits required to recover the internal states of the LFSRs. Our work demonstrates an approximately linear relationship...

In the interconnected global financial system, anti-money laundering (AML) and combating the financing of terrorism (CFT) regulations are indispensable for safeguarding financial integrity. However, while illicit transactions constitute only a small fraction of overall financial activities, traditional AML/CFT frameworks impose uniform compliance burdens on all users, resulting in inefficiencies, transaction delays, and privacy concerns. These issues stem from the institution-centric...

This paper examines the deployment of Multi-Party Computation (MPC) in corporate data processing environments, focusing on its legal and technical implications under the European Union’s General Data Protection Regulation (GDPR). By combining expertise in cryptography and legal analysis, we address critical questions necessary for assessing the suitability of MPC for real-world applications. Our legal evaluation explores the conditions under which MPC qualifies as an anonymizing approach...

Fault attacks pose a significant threat to cryptographic implementations, motivating the development of countermeasures, primarily based on a combination of redundancy and masking techniques. Redundancy, in these countermeasures, is often implemented via duplication or linear codes. However, their inherent structure remains susceptible to strategic fault injections bypassing error checks. To address this, the CAPA countermeasure from CRYPTO 2018 leveraged information-theoretic MAC tags for...

Advanced Encryption Standard (AES) is one of the most widely used and extensively studied encryption algorithms globally, which is renowned for its efficiency and robust resistance to attacks. In this paper, three quantum circuits are designed to implement the S-box, which is the sole nonlinear component in AES. By incorporating a linear key schedule, we achieve a quantum circuit for implementing AES with the minimum number of qubits used. As a consequence, only 264/328/398 qubits are needed...

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...

Practical signature-based witness encryption (SWE) schemes recently emerged as a viable alternative to instantiate timed-release cryptography in the honest majority setting. In particular, assuming threshold trust in a set of parties that release signatures at a specified time, one can ``encrypt to the future'' using an SWE scheme. Applications of SWE schemes include voting, auctions, distributed randomness beacons, and more. However, the lack of homomorphism in existing SWE schemes reduces...

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...

The Message Layer Security (MLS) protocol has recently been standardized by the IETF. MLS is a scalable secure group messaging protocol expected to run more efficiently compared to the Signal protocol at scale, while offering a similar level of strong security. Even though MLS has undergone extensive examination by researchers, the majority of the works have focused on confidentiality. In this work, we focus on the authenticity of the application messages exchanged in MLS. Currently, MLS...

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,...

Abdalla et al. (ASIACRYPT 2020) introduced a notion of identity-based inner-product functional encryption (IBIPFE) that combines identity-based encryption and inner-product functional encryption (IPFE). Thus far, several pairing-based and lattice-based IBIPFE schemes have been proposed. However, there are two open problems. First, there are no known IBIPFE schemes that satisfy the adaptive simulation-based security. Second, known IBIPFE schemes that satisfy the adaptive...

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...

Cryptographic group actions provide simple post-quantum generalizations to many cryptographic protocols based on the discrete logarithm problem (DLP). However, many advanced group action-based protocols do not solely rely on the core group action problem (the so-called vectorization problem), but also on variants of this problem, to either improve efficiency or enable new functionalities. In particular, the security of the CSI-SharK threshold signature protocol relies on the Vectorization...

Oblivious Transfer (OT) is a fundamental cryptographic primitive introduced nearly four decades ago. OT allows a receiver to select and learn $t$ out of $n$ private messages held by a sender. It ensures that the sender does not learn which specific messages the receiver has chosen, while the receiver gains no information about the remaining $n − t$ messages. In this work, we introduce the notion of functional OT (FOT), for the first time. FOT adds a layer of security to the conventional OT...

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...

Lattice trapdoor algorithms allow us to sample hard random lattices together with their trapdoors, given which short lattice vectors can be sampled efficiently. This enables a wide range of advanced cryptographic primitives. In this work, we ask: can we distribute lattice trapdoor algorithms non-interactively? We study a natural approach to sharing lattice trapdoors: splitting them into partial trapdoors for different lower-rank sublattices which allow the local sampling of short...

Non-interactive zero-knowledge (NIZK) arguments allow a prover to convince a verifier about the truthfulness of an NP-statement by sending just one message, without disclosing any additional information. In several practical scenarios, the Fiat-Shamir transform is used to convert an efficient constant-round public-coin honest-verifier zero-knowledge proof system into an efficient NIZK argument system. This approach is provably secure in the random oracle model, crucially requires the...

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...

Multi-signatures allow a set of parties to produce a single signature for a common message by combining their individual signatures. The result can be verified using the aggregated public key that represents the group of signers. Very recent work by Lehmann and Özbay (PKC '24) studied the use of multi-signatures for ad-hoc privacy-preserving group signing, formalizing the notion of multi-signatures with probabilistic yet verifiable key aggregation. Moreover, they proposed new BLS-type...

Oblivious pseudorandom functions (OPRFs) are an important primitive in privacy-preserving cryptographic protocols. The growing interest in OPRFs, both in theory and practice, has led to the development of numerous constructions and variations. However, most of these constructions rely on classical assumptions. Potential future quantum attacks may limit the practicality of those OPRFs for real-world applications. To close this gap, we introduce Leap, a novel OPRF based on heuristic...

The Fiat–Shamir transformation is a fundamental cryptographic technique widely used to convert public-coin interactive protocols into non-interactive ones. This transformation is crucial in both theoretical and practical applications, particularly in the construction of succinct non-interactive arguments (SNARKs). While its security is well-established in the random oracle model, practical implementations replace the random oracle with a concrete hash function, where security is merely...

Recent applications and attacks have highlighted the need for authenticated encryption (AE) schemes to achieve the so-called committing security beyond privacy and authenticity. As a result, several generic solutions have been proposed to transform a non-committing AE scheme to a committing one, for both basic unique-nonce security and advanced misuse-resistant (MR) security. We observe that all existing practical generic transforms are subject to at least one of the following limitations:...

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...

We propose new techniques for enhancing the efficiency of $\Sigma$-protocols in lattice settings. One major challenge in lattice-based $\Sigma$-protocols is restricting the norm of the extracted witness in soundness proofs. Most of existing solutions either repeat the protocol several times or opt for a relaxation version of the original relation. Recently, Boneh and Chen have proposed an innovative solution called $\mathsf{LatticeFold}$, which utilizes a sum-check protocol to...

Indistinguishability obfuscation (\iO) is a powerful cryptographic primitive and has been quoted as the ``swiss army-knife of modern cryptography''. Most prior works on \iO focused on theoretical feasibility, and paid less attention to the efficiency of the constructions. As a result, all prior constructions stopped at achieving polynomial efficiency without worrying about how large the polynomial is. In fact, it has even been conjectured that a polynomial dependence on the input...

Zero-Knowledge Succinct Non-interactive Arguments of Knowledge (zkSNARKs) lead to proofs that can be succinctly verified but require huge computational resources to generate. Prior systems outsource proof generation either through public delegation, which reveals the witness to the third party, or, more preferably, private delegation that keeps the witness hidden using multiparty computation (MPC). However, current private delegation schemes struggle with scalability and efficiency due to...

Syndrome decoding (SD), and equivalently Learning Parity with Noise (LPN), is a fundamental problem in cryptography, which states that for a field $\mathbb{F}$, some compressing public matrix $\mathbf{G} \in \mathbb{F}^{k\times n}$, and a secret sparse vector $\mathbf{e} \in\mathbb{F}^{n}$ sampled from some noise distribution, $\mathbf{G}\mathbf{e}$ is indistinguishable from uniform. Recently, the SD has gained significant interest due to its use in pseudorandom correlation generators...

Komargodski et. al. defined evolving secret-sharing schemes with an unbounded number of parties. In this model, parties arrive one after the other and the number of parties that will arrive is not known. Another cryptographic primitive related to secret-sharing is conditional disclosure of secrets protocols (CDS) that defined by Gertner et. al. A CDS protocol for a Boolean function $f$ involves $k$ servers and a referee. Each server holds a common secret $s$, a common random string $r$,...

Blockchain interoperability solutions allow users to hold and transfer assets among different chains, and in so doing reap the benefits of each chain. To fully reap the benefits of multi-chain financial operations, it is paramount to support interoperability and cross-chain transactions also on Layer-2 networks, in particular payment channel networks (PCNs). Nevertheless, existing works on Layer-2 interoperability solutions still involve on-chain events, which limits their scalability and...

The study of attack algorithms for the Learning with Errors (LWE) problem is crucial for the cryptanalysis of LWE-based cryptosystems. The BKW algorithm has gained significant attention as an important combinatorial attack for solving LWE. However, its exponential time and memory requirements severely limit its practical applications, even with medium-sized parameters. In this paper, we present a memory-efficient BKW algorithm for LWE, which extends Bogos's work [Asiacrypt'16] on the...

Publicly identifiable abort is a critical feature for ensuring accountability in outsourced computations using secure multiparty computation (MPC). Despite its importance, no prior work has specifically addressed identifiable abort in the context of outsourced computations. In this paper, we present the first MPC protocol that supports publicly identifiable abort with minimal overhead for external clients. Our approach minimizes client-side computation by requiring only a few pseudorandom...

Floating-point arithmetic plays a central role in computer science and is used in various domains where precision and computational scale are essential. One notable application is in machine learning, where Fully Homomorphic Encryption (FHE) can play a crucial role in safeguarding user privacy. In this paper, we focus on TFHE and develop novel homomorphic operators designed to enable the construction of precise and adaptable homomorphic floating-point operations. Integrating floating-point...

Current adaptively secure identity-based encryption (IBE) constructions from lattices are unable to achieve a good balance among the master public key size, secret key size, modulus and reduction loss. All existing lattice-based IBE schemes share a common restriction: the modulus is quadratic in the trapdoor norm. In this work, we remove this restriction and present a new adaptively secure IBE scheme from lattices in the standard model, which improves the state-of-the-art construction...

The rapid advancement of quantum computing has ushered in a new era of post-quantum cryptography, urgently demanding quantum-resistant digital signatures to secure modern communications and transactions. Among NIST-standardized candidates, Falcon—a compact lattice-based signature scheme—stands out for its suitability in size-sensitive applications. In this paper, we present cuFalcon, a high-throughput GPU implementation of Falcon that addresses its computational bottlenecks through adaptive...

Cryptographic proof systems enable a verifier to be convinced of of a computation's correctness without re-executing it; common efficiency requirements include both succinct proofs and fast verification. In this work we put forth the general study of cryptographic proof systems with sublinear proving time (after a preprocessing). Prior work has achieved sublinear proving only for limited computational settings (e.g., vector commitments and lookup arguments), relying on specific...

Isogeny-based cryptography relies its security on the hardness of the supersingular isogeny problem: finding an isogeny between two supersingular curves defined over a quadratic field. The Delfs-Galbraith algorithm is the most efficient procedure for solving the supersingular isogeny problem with a time complexity of $\tilde{\mathcal{O}}(p^{1/2})$ operations. The bottleneck of the Delfs-Galbraith algorithm is the so-called subfield curve search (i.e., finding an isogenous supersingular...