Pseudorandom codes are error-correcting codes with the property that no efficient adversary can distinguish encodings from uniformly random strings. They were recently introduced by Christ and Gunn [CRYPTO 2024] for the purpose of watermarking the outputs of randomized algorithms, such as generative AI models. Several constructions of pseudorandom codes have since been proposed, but none of them are robust to error channels that depend on previously seen codewords. This stronger kind of...

Secure aggregation is the distributed task of securely computing a sum of values (or a vector of values) held by a set of parties, revealing only the output (i.e., the sum) in the computation. Existing protocols, such as Prio (NDSI’17), Prio+ (SCN’22), Elsa (S&P’23), and Whisper (S&P’24), support secure aggregation with input validation to ensure inputs belong to a specified domain. However, when malicious servers are present, these protocols primarily guarantee privacy but not input...

Pseudo-Random Injections (PRIs) have had several applications in symmetric-key cryptography, such as in the idealization of Authenticated Encryption with Associated Data (AEAD) schemes, building robust AEAD, and, recently, in converting a committing AEAD scheme into a succinctly committing AEAD scheme. In Crypto 2024, Bellare and Hoang showed that if an AEAD scheme is already committing, it can be transformed into a succinctly committed scheme by encrypting part of the plaintext using a PRI....

\textit{Federated Learning} (FL) is a distributed machine learning paradigm that allows multiple clients to train models collaboratively without sharing local data. Numerous works have explored security and privacy protection in FL, as well as its integration with blockchain technology. However, existing FL works still face critical issues. \romannumeral1) It is difficult to achieving \textit{poisoning robustness} and \textit{data privacy} while ensuring high \textit{model accuracy}....

In this paper, we introduce zkMarket, a privacy-preserving fair trade system on the blockchain. zkMarket addresses the challenges of transaction privacy and computational efficiency. To ensure transaction privacy, zkMarket is built upon an anonymous transfer protocol. By combining encryption with zero-knowledge succinct non-interactive arguments of knowledge (zk-SNARK), both the seller and the buyer are enabled to trade fairly. Furthermore, by encrypting the decryption key, we make the data...

Distributed mean estimation (DME) is a fundamental and important task as it serves as a subroutine in convex optimization, aggregate statistics, and, more generally, federated learning. The inputs for distributed mean estimation (DME) are provided by clients (such as mobile devices), and these inputs often contain sensitive information. Thus, protecting privacy and mitigating the influence of malicious adversaries are critical concerns in DME. A surge of recent works has focused on building...

In a zero-knowledge proof market, we have two sides. On one side, bidders with proofs of different sizes and some private value to have this proof computed. On the other side, we have distributors (also called sellers) which have compute available to process the proofs by the bidders, and these distributors have a certain private cost to process these proofs (dependent on the size). More broadly, this setting applies to any online resource allocation where we have bidders who desire a...

The recent explosion of high-quality language models has necessitated new methods for identifying AI-generated text. Watermarking is a leading solution and could prove to be an essential tool in the age of generative AI. Existing approaches embed watermarks at inference and crucially rely on the large language model (LLM) specification and parameters being secret, which makes them inapplicable to the open-source setting. In this work, we introduce the first watermarking scheme for...

Fully asynchronous multi-party computation (AMPC) has superior robustness in realizing privacy and guaranteed output delivery (G.O.D.) against asynchronous adversaries that can arbitrarily delay communications. However, none of these protocols are truly practical, as they either have sub-optimal resilience, incur cumbersome communication cost, or suffer from an online phase with extra cryptographic overhead. The only attempting implementation---HoneyBadgerMPC (hbMPC)---merely ensures G.O.D....

This work conducts a comprehensive investigation on determining the entropic hardness of (R/M)LWR under polynomial modulus. Particularly, we establish the hardness of (M)LWR for general entropic secret distributions from (Module) LWE assumptions based on a new conceptually simple framework called rounding lossiness. By combining this hardness result and a trapdoor inversion algorithm with asymptotically the most compact parameters, we obtain a compact lossy trapdoor function (LTF) with...

Large language models (LLMs) have recently transformed many industries, enhancing content generation, customer service agents, data analysis and even software generation. These applications are often hosted on remote servers to protect the neural-network model IP; however, this raises concerns about the privacy of input queries. Fully Homomorphic Encryption (FHE), an encryption technique that allows for computations on private data, has been proposed as a solution to the challenge....

This paper addresses verifiable consensus of pre-processed circuit polynomials for succinct non-interactive argument of knowledge (SNARK). More specifically, we focus on parts of circuits, referred to as wire maps, which may change based on program inputs or statements being argued. Preparing commitments to wire maps in advance is essential for certain SNARK protocols to maintain their succinctness, but it can be costly. SNARK verifiers can alternatively consider receiving wire maps from an...

The theory of compressed $\Sigma$-protocols [AC20, ACF21] provides a standardized framework for creating efficient $\Sigma$-protocols. This method involves two main phases: first, amortization, which combines multiple instances that satisfy a homomorphic relation into a single instance; and second, Bulletproofs compression [BBB+18], which minimizes communication overhead to a logarithmic scale during the verification of the combined instance. For high-degree polynomial (non-homomorphic)...

Traditional secure multiparty computation (MPC) protocols presuppose a fixed set of participants throughout the computational process. To address this limitation, Fluid MPC [CRYPTO 2021] presents a dynamic MPC model that allows parties to join or exit during circuit evaluation dynamically. However, existing dynamic MPC protocols can guarantee safety but not liveness within asynchronous networks. This paper introduces ΠAD-MPC, a fully asynchronous dynamic MPC protocol. ΠAD-MPC ensures both...

Masking schemes are key in thwarting side-channel attacks due to their robust theoretical foundation. Transitioning from Boolean to arithmetic (B2A) masking is a necessary step in various cryptography schemes, including hash functions, ARX-based ciphers, and lattice-based cryptography. While there exists a significant body of research focusing on B2A software implementations, studies pertaining to hardware implementations are quite limited, with the majority dedicated solely to creating...

In this paper, we introduce a novel approach to Multi-Key Fully Homomorphic Encryption (MK-FHE) that enhances both efficiency and security beyond the capabilities of traditional MK-FHE and MultiParty Computation (MPC) systems. Our method generates a unified key structure, enabling constant ciphertext size and constant execution time for encrypted computations, regardless of the number of participants involved. This approach addresses critical limitations such as ciphertext size expansion,...

We present the first undetectable watermarking scheme for generative image models. Undetectability ensures that no efficient adversary can distinguish between watermarked and un-watermarked images, even after making many adaptive queries. In particular, an undetectable watermark does not degrade image quality under any efficiently computable metric. Our scheme works by selecting the initial latents of a diffusion model using a pseudorandom error-correcting code (Christ and Gunn, 2024), a...

Peer-to-peer energy trading markets enable users to exchange electricity, directly offering them increased financial benefits. However, discrepancies often arise between the electricity volumes committed to in trading auctions and the volumes actually consumed or injected. Solutions designed to address this issue often require access to sensitive information that should be kept private. This paper presents a novel, fully privacy-preserving billing protocol designed to protect users'...

There has been a recent interest to develop and standardize Robust Authenticated Encryption (Robust AE) schemes. NIST, for example, is considering an Accordion mode (a wideblock tweakable blockcipher), with Robust AE as a primary application. On the other hand, recent attacks and applications suggest that encryption needs to be committing. Indeed, committing security isalso a design consideration in the Accordion mode. Yet it is unclear how to build a Robust AE with committing security....

XCB, a tweakable enciphering mode, is part of IEEE Std. 1619.2 for shared storage media. We show that all versions of XCB are not secure through three plaintext recovery attacks. A key observation is that XCB behaves like an LRW1-type tweakable block cipher for single-block messages, which lacks CCA security. The first attack targets one-block XCB, using three queries to recover the plaintext. The second one requires four queries to recover the plaintext that excludes one block. The last one...

Overpass Channels presents a groundbreaking approach to blockchain scalability, offering a horizontally scalable, privacy-enhanced payment network with independent verification, fluid liquidity, and robust censorship resistance. This paper introduces a novel architecture that leverages zero-knowledge proofs, specifically zk-SNARKs, to ensure transaction validity and privacy while enabling unprecedented throughput and efficiency. By eliminating the need for traditional consensus mechanisms...

Lookup arguments enable a prover to convince a verifier that a committed vector of lookup elements $\vec{f} \in \mathbb{F}^m$ is contained within a predefined table $T \in \mathbb{F}^N$. These arguments are particularly beneficial for enhancing the performance of SNARKs in handling non-arithmetic operations, such as batched range checks or bitwise operations. While existing works have achieved efficient and succinct lookup arguments, challenges remain, particularly when dealing with large...

In the context of secure multiparty computation (MPC) protocols with guaranteed output delivery (GOD) for the honest majority setting, the state-of-the-art in terms of communication is the work of (Goyal et al. CRYPTO'20), which communicates O(n|C|) field elements, where |C| is the size of the circuit being computed and n is the number of parties. Their round complexity, as usual in secret-sharing based MPC, is proportional to O(depth(C)), but only in the optimistic case where there is no...

This article presents an in-depth study of isogeny-based cryptographic methods for the development of secure and scalable electronic voting systems. We address critical challenges such as voter privacy, vote integrity, and resistance to quantum attacks. Our work introduces novel cryptographic protocols leveraging isogenies, establishing a robust framework for post-quantum secure electronic voting. We provide detailed mathematical foundations, protocol designs, and security proofs,...

True Random Number Generators (TRNGs) and Physically Unclonable Functions (PUFs) are critical hardware primitives for cryptographic systems, providing randomness and device-specific security. TRNGs require complete randomness, while PUFs rely on consistent, device-unique responses. In this work, both primitives are implemented on a System-on-Chip Field-Programmable Gate Array (SoC FPGA), leveraging the integrated Phase-Locked Loops (PLLs) for robust entropy generation in PLLbased TRNGs. A...

Cryptography is a crucial method for ensuring the security of communication and data transfers across networks. While it excels on devices with abundant resources, such as PCs, servers, and smartphones, it may encounter challenges when applied to resource-constrained Internet of Things (IoT) devices like Radio Frequency Identification (RFID) tags and sensors. To address this issue, a demand arises for a lightweight variant of cryptography known as lightweight cryptography (LWC). In...

Phase-locked loops (PLLs) integrated within field-programmable gate arrays (FPGAs) or System-on-Chip FPGAs (SoCs) represent a promising approach for generating random numbers. Their widespread deployment, isolated functionality within these devices, and robust entropy, as demonstrated in prior studies, position PLL-based true random number generators (PLL-TRNGs) as highly viable solutions for this purpose. This study explicitly examines PLL-TRNG implementations using the ZC702 Rev1.1...

Anamorphic encryptions and anamorphic signatures assume a double key pre-shared between two parties so as to enable the transmission of covert messages. How to securely and efficiently distribute a double key under the dictator's surveillance is a central problem for anamorphic cryptography, especially when the users are forced to surrender their long-term secret keys or even the randomness used in the algorithms to the dictator. In this paper, we propose Anamorphic Authentication Key...

In Side-Channel Analysis (SCA), statistical or machine learning methods are employed to extract secret information from power or electromagnetic (EM) traces. In many practical scenarios, raw power/EM traces can span hundreds of thousands of features, with relevant leakages occurring over only a few small segments. Consequently, existing SCAs often select a small number of features before launching the attack, making their success highly dependent on the feasibility of feature selection....

Federated Learning (FL) enables multiple clients to collaboratively train a machine learning model while keeping their data private, eliminating the need for data sharing. Two common approaches to secure aggregation (SA) in FL are the single-aggregator and multiple-aggregator models. This work focuses on improving the multiple-aggregator model. Existing multiple-aggregator protocols such as Prio (NSDI 2017), Prio+ (SCN 2022), Elsa (S&P 2023) either offer robustness only in the...

Introduced in [CG24], pseudorandom error-correcting codes (PRCs) are a new cryptographic primitive with applications in watermarking generative AI models. These are codes where a collection of polynomially many codewords is computationally indistinguishable from random, except to individuals with the decoding key. In this work, we examine the assumptions under which PRCs with robustness to a constant error rate exist. 1. We show that if both the planted hyperloop assumption...

We propose waterlogs, a new direction to detect and trace synthetic text outputs from large language models based on transparency logs. Waterlogs offer major categorical advantages over watermarking: it (1) allows for the inclusion of arbitrary metadata to facilitate tracing, (2) is publicly verifiable by third parties, and (3) operates in a distributed manner while remaining robust and efficient. Waterlogs rely on a verifiable Hamming distance index, a novel data structure that we...

This paper studies the provable security of the deterministic random bit generator~(DRBG) utilized in Linux 6.4.8, marking the first analysis of Linux-DRBG from a provable security perspective since its substantial structural changes in Linux 4 and Linux 5.17. Specifically, we prove its security up to $O(\min\{2^{\frac{n}{2}},2^{\frac{\lambda}{2}}\})$ queries in the seedless robustness model, where $n$ is the output size of the internal primitives and $\lambda$ is the min-entropy of the...

We present the first Key Policy Attribute-Based Encryption (KP-ABE) scheme employing isogeny-based cryptography through class group actions, specifically utilizing the Csi-FiSh instantiation and pairing groups. We introduce a new assumption, denoted Isog-DLin, which combines the isogeny and DLin assumptions. We propose the following constructions: a small universe KP-ABE and a large universe KP-ABE under the Isog-DBDH assumption, and a small universe KP-ABE under the Isog-DLin assumption. In...

Clarifying the robustness of authenticated encryption (AE) schemes, such as security under nonce misuse or Release of Unverified Plaintext (RUP), is critically important due to the extensive use of AEs in real-world applications. We present a comprehensive analysis of the robustness of well-known standards, namely GCM, CCM, and OCB3. Despite many existing studies, we uncovered several robustness properties for them that were not known in the literature. In particular, we show that both...

Robust message authentication codes (MACs) and authenticated encryption (AE) schemes that provide authenticity in the presence of side-channel leakage are essential primitives. These constructions often rely on primitives designed for strong leakage protection, among others including the use of strong-unpredictable (tweakable) block-ciphers. This paper extends the strong-unpredictability security definition to the versatile and new forkcipher primitive. We show how to construct secure and...

This paper presents Raccoon, a lattice-based signature scheme submitted to the NIST 2022 call for additional post-quantum signatures. Raccoon has the specificity of always being masked. Concretely, all sensitive intermediate values are shared into 𝑑 parts. The main design rationale of Raccoon is to be easy to mask at high orders, and this dictated most of its design choices, such as the introduction of new algorithmic techniques for sampling small errors. As a result, Raccoon achieves a...

We consider protocols for secure multi-party computation (MPC) built from FHE under honest majority, i.e., for $n=2t+1$ players of which $t$ are corrupt, that are robust. Surprisingly there exists no robust threshold FHE scheme based on BFV to design such MPC protocols. Precisely, all existing methods for generating a common relinearization key can abort as soon as one player deviates. We address this issue, with a new relinearization key (adapted from [CDKS19, CCS'19]) which we show how to...

Masking has become a widely applied and heavily researched method to protect cryptographic implementations against SCA attacks. The success of masking is primarily attributed to its strong theoretical foundation enabling it to formally prove security by modeling physical properties through so-called probing models. Specifically, the robust $d$-probing model enables us to prove the security for arbitrarily masked hardware circuits, manually or with the assistance of automated tools, even when...

The recent VOLE-based interactive zero-knowledge (VOLE-ZK) protocols along with non-interactive zero-knowledge (NIZK) proofs based on MPC-in-the-Head (MPCitH) and VOLE-in-the-Head (VOLEitH) extensively utilize the commitment schemes, which adopt a circular correlation robust (CCR) hash function as the core primitive. Nevertheless, the state-of-the-art CCR hash construction by Guo et al. (S&P'20), building from random permutations, can only provide 128-bit security, when it is instantiated...

We propose a new wide encryption (WE) mode of operation that satisfies robust authenticated encryption (RAE) and committing security with minimum ciphertext expansion. WE is attracting much attention in the last few years, and its advantage includes RAE security that provides robustness against wide range of misuses, combined with the encode-then-encipher (EtE) construction. Unfortunately, WE-based EtE does not provide good committing security, and there is a recent constant-time CMT-4...

Considering side-channel analysis (SCA) security for cryptographic devices, the mitigation of electromagnetic leakage and electromagnetic interference (EMI) between modules poses significant challenges. This paper presents a comprehensive review and deep analysis of the utilization of EMI shielding materials, devised for reliability purposes and standards such as EMI/EMC, as a countermeasure to enhance EM-SCA security. We survey the current landscape of EMI-shields materials, including...

In this work, we continue the analysis of the binding properties of implicitly-rejecting key-encapsulation mechanisms (KEMs) obtained via the Fujisaki-Okamoto (FO) transform. These binding properties, in earlier literature known under the term robustness, thwart attacks that can arise when using KEMs in larger protocols. Recently, Cremers et al. (ePrint'24) introduced a framework for binding notions, encompassing previously existing but also new ones. While implicitly-rejecting KEMs have...

Side-channel-analysis (SCA) resistance with cost optimization in AES hardware implementations remains a significant challenge. While traditional masking-based schemes offer provable security, they often incur substantial resource overheads (latency, area, randomness, performance, power consumption). Alternatively, the RAMBAM scheme introduced a redundancy-based approach to control the signal-to-noise ratio, and achieves exponential leakage reduction as redundancy increases. This method...

Blockchain technology ensures accountability, transparency, and redundancy in critical applications, includ- ing IoT with embedded systems. However, the reliance on public-key cryptography (PKC) makes blockchain vulnerable to quantum computing threats. This paper addresses the urgent need for quantum-safe blockchain solutions by integrating Post- Quantum Cryptography (PQC) into blockchain frameworks. Utilizing algorithms from the NIST PQC standardization pro- cess, we aim to fortify...

This paper presents a novel reduction from the average-case hardness of the Module Inhomogeneous Short Integer Solution (M-ISIS) problem to the worst-case hardness of the Closest Vector Problem (CVP) by defining and leveraging “perfect” lattices for cryptographic purposes. Perfect lattices, previously only theoretical constructs, are characterized by their highly regular structure, optimal density, and a central void, which we term the “Origin Cell.” The simplest Origin Cell is a...

Enhancing privacy in federal learning (FL) without considering robustness can create an open door for attacks such as poisoning attacks on the FL process. Thus, addressing both the privacy and security aspects simultaneously becomes vital. Although, there are a few solutions addressing both privacy and security in the literature in recent years, they have some drawbacks such as requiring two non-colluding servers, heavy cryptographic operations, or peer-to-peer communication topology. In...

Cryptocurrencies and blockchain technology provide an innovative model for reshaping digital services. Driven by the movement toward Web 3.0, recent systems started to provide distributed services, such as computation outsourcing or file storage, on top of the currency exchange medium. By allowing anyone to join and collect cryptocurrency payments for serving others, these systems create decentralized markets for trading digital resources. Yet, there is still a big gap between the promise of...

MPC-in-the-Head (MPCitH) has recently gained traction as a foundation for post-quantum signature schemes, offering robust security without trapdoors. Despite its strong security profile, MPCitH-based schemes suffer from high computational overhead and large signature sizes, limiting their practical application. This work addresses these inefficiencies by relaxing vector commitments within MPCitH-based schemes. We introduce the concept of vector semi-commitment, which relaxes the binding...

Private Information Retrieval (PIR) enables a client to retrieve a database element from a semi-honest server while hiding the element being queried from the server. Maliciously-secure PIR (mPIR) [Colombo et al., USENIX Security '23] strengthens the guarantees of plain (i.e., semi-honest) PIR by ensuring that even a misbehaving server (a) cannot compromise client privacy via selective-failure attacks, and (b) must answer every query *consistently* (i.e., with respect to the same database)....

We propose a new framework based on random submersions — that is projection over a random subspace blinded by a small Gaussian noise — for constructing verifiable short secret sharing and showcase it to construct efficient threshold lattice-based signatures in the hash-and-sign paradigm, when based on noise flooding. This is, to our knowledge, the first hash-and-sign lattice-based threshold signature. Our threshold signature enjoys the very desirable property of robustness, including at key...

Secure Aggregation (SA) stands as a crucial component in modern Federated Learning (FL) systems, facilitating collaborative training of a global machine learning model while protecting the privacy of individual clients' local datasets. Many existing SA protocols described in the FL literature operate synchronously, leading to notable runtime slowdowns due to the presence of stragglers (i.e. late-arriving clients). To address this challenge, one common approach is to consider stragglers as...

Motivated by the problem of detecting AI-generated text, we consider the problem of watermarking the output of language models with provable guarantees. We aim for watermarks which satisfy: (a) undetectability, a cryptographic notion introduced by Christ, Gunn & Zamir (2024) which stipulates that it is computationally hard to distinguish watermarked language model outputs from the model's actual output distribution; and (b) robustness to channels which introduce a constant fraction of...

In the *Distributed Secret Sharing Generation* (DSG) problem $n$ parties wish to obliviously sample a secret-sharing of a random value $s$ taken from some finite field, without letting any of the parties learn $s$. *Distributed Key Generation* (DKG) is a closely related variant of the problem in which, in addition to their private shares, the parties also generate a public ``commitment'' $g^s$ to the secret. Both DSG and DKG are central primitives in the domain of secure multiparty...

The Keyed Hashing and Asymmetric Nonce (KHAN) encryption algorithm is a novel cryptographic scheme that utilizes the unique properties of full reptend prime numbers. This paper details the algorithm, its theoretical foundations, and the rigorous proofs of its security properties. By leveraging the characteristics of cyclic sequences derived from full reptend primes, KHAN provides robust encryption with high resistance to cryptanalytic attacks.

In this paper, we study the robustness of Kyber, the Learning With Errors (LWE)-based Key Encapsulation Mechanism (KEM) chosen for standardization by NIST, against key mismatch attacks. We demonstrate that Kyber's security levels can be compromised with a few mismatch queries by striking a balance between the parallelization level and the cost of lattice reduction for post-processing. This highlights the imperative need to strictly prohibit key reuse in CPA-secure Kyber. We further...

We study watermarking schemes for language models with provable guarantees. As we show, prior works offer no robustness guarantees against adaptive prompting: when a user queries a language model more than once, as even benign users do. And with just a single exception (Christ and Gunn, 2024), prior works are restricted to zero-bit watermarking: machine-generated text can be detected as such, but no additional information can be extracted from the watermark. Unfortunately, merely detecting...

The hardness of Kolmogorov complexity is intricately connected to the existence of one-way functions and derandomization. An important and elegant notion is Levin's version of Kolmogorov complexity, \(\mathsf{Kt}\), and its decisional variant, \(\mathsf{MKtP}\). The question whether \(\mathsf{MKtP}\) can be computed in polynomial time is particularly interesting because it is not subject to known technical barriers such as algebrization or natural proofs that would explain the lack of a...

Asynchronous Verifiable Information Dispersal (AVID) allows a dealer to disperse a message $M$ across a collection of server replicas consistently and efficiently, such that any future client can reliably retrieve the message $M$ if some servers fail. Since AVID was introduced by Cachin and Tessaro in 2005, several works improved the asymptotic communication complexity of AVID protocols. However, recent gains in communication complexity have come at the expense of sub-optimal storage,...

Vertical Federated Learning (VFL) is becoming a standard collaborative learning paradigm with various practical applications. Randomness is essential to enhancing privacy in VFL, but introducing too much external randomness often leads to an intolerable performance loss. Instead, as it was demonstrated for other federated learning settings, leveraging internal randomness —as provided by variational autoencoders (VAEs) —can be beneficial. However, the resulting privacy has never been...

To introduce a post-quantum-secure encryption scheme specifically for use in flight-computers, we used avionics’ module-isolation methods to wrap a recent encryption standard (HPKE – Hybrid Public Key Encryption) within a software partition. This solution proposes an upgrade to HPKE, using quantum-resistant ciphers (Kyber/ML-KEM and Dilithium/ML-DSA) redundantly alongside well-established ciphers, to achieve post-quantum security. Because cryptographic technology can suddenly become...

he unique design of the FLIP cipher necessitated a generalization of standard cryptographic criteria for Boolean functions used in stream ciphers, prompting a focus on properties specific to subsets of $\mathbb{F}_2^n$ rather than the entire set. This led to heightened interest in properties related to fixed Hamming weight sets and the corresponding partition of $\mathbb{F}_2^n$ into n+1 such sets. Consequently, the concept of Weightwise Almost Perfectly Balanced (WAPB) functions emerged,...

Existing oblivious systems offer robust security by concealing memory access patterns, but they encounter significant scalability and performance challenges. Recent efforts to enhance the practicality of these systems involve embedding oblivious computation, e.g., oblivious sorting and shuffling, within Trusted Execution Environments (TEEs). For instance, oblivious sort has been heavily utilized: in Oblix (S&P'18), when oblivious indexes are created and accessed; in Snoopy's high-throughput...

Security proofs for cryptographic primitives typically assume operations are executed in the correct sequence; however, insecure implementations or software-level attacks can disrupt control flows, potentially invalidating these guarantees. To address this issue, we introduce a new security notion, IND-CFA, which formalizes decryption security in the presence of adversarially controlled execution flows. Using this notion, we investigate the control flows under which a cryptographic scheme...

This paper presents a novel blockchain-based decentralized identity system (DID), tailored for enhanced digital identity management in Internet of Things (IoT) and device-to-device (D2D) networks. The proposed system features a hierarchical structure that effectively merges a distributed ledger with a mobile D2D network, ensuring robust security while streamlining communication. Central to this design are the gateway nodes, which serve as intermediaries, facilitating DID registration and...

Dynamic Decentralized Functional Encryption (DDFE), introduced by Chotard et al. (CRYPTO'20), represents a robust generalization of (Multi-Client) Functional Encryption. It allows users to dynamically join and contribute private inputs to individually controlled joint functions without requiring a trusted authority. Recently, Shi et al. (PKC'23) proposed the first Multi-Client Functional Encryption scheme for function-hiding inner products (FH-IP) without relying on random oracles....

In this paper we address the use of Neural Networks (NN) for the assessment of the quality and hence safety of several Random Number Generators (RNGs), focusing both on the vulnerability of classical Pseudo Random Number Generators (PRNGs), such as Linear Congruential Generators (LCGs) and the RC4 algorithm, and extending our analysis to non-conventional data sources, such as Quantum Random Number Generators (QRNGs) based on Vertical-Cavity Surface- Emitting Laser (VCSEL). Among the...

This paper presents an in-depth exploration of the development and deployment of a Layer 1 (L1) blockchain designed to underpin metaverse experiences. As the digital and physical realms become increasingly intertwined, the metaverse emerges as a frontier for innovation, demanding robust, scalable, and secure infrastructure. The core of our investigation centers around the challenges and insights gained from constructing a blockchain framework capable of supporting the vast, dynamic...

Zero-Knowledge Proof (ZKP) technology marks a revolutionary advancement in the field of cryptography, enabling the verification of certain information ownership without revealing any specific details. This technology, with its paradoxical yet powerful characteristics, provides a solid foundation for a wide range of applications, especially in enhancing the privacy and security of blockchain technology and other cryptographic systems. As ZKP technology increasingly becomes a part of the...

Oblivious message retrieval (OMR) allows resource-limited recipients to outsource the message retrieval process without revealing which messages are pertinent to which recipient. Its realizations in recent works leave an open problem: can an OMR scheme be both practical and provably secure against spamming attacks from malicious senders (i.e., DoS-resistant) under standard assumptions? In this paper, we first prove that a prior construction $\mathsf{OMRp2}$ is DoS-resistant under a...

SHA2 is widely used in various traditional public key ryptosystems, post-quantum cryptography, personal identification, and network communication protocols. Therefore, ensuring its robust security is of critical importance. Several differential fault attacks based on random word fault have targeted SHA1 and SHACAL-2. However, extending such random word-based fault attacks to SHA2 proves to be much more difficult due to the increased complexity of the Boolean functions in SHA2. In this...

Lattice-based cryptography has emerged as a promising new candidate to build cryptographic primitives. It offers resilience against quantum attacks, enables fully homomorphic encryption, and relies on robust theoretical foundations. Zero-knowledge proofs (ZKPs) are an essential primitive for various privacy-preserving applications. For example, anonymous credentials, group signatures, and verifiable oblivious pseudorandom functions all require ZKPs. Currently, the majority of ZKP systems are...

The Bitcoin ecosystem has continued to evolve beyond its initial promises of decentralization, transparency, and security. Recent advancements have notably been made with the integration of Layer-2 solutions, which address scalability issues by offloading transactions from the main blockchain. This facilitates faster and more cost-effective transactions while maintaining integrity. The advent of inscriptions and ordinal protocols has further broadened the spectrum of capabilities, enabling...

The (parallel) classical black pebbling game is a helpful abstraction which allows us to analyze the resources (time, space, space-time, cumulative space) necessary to evaluate a function $f$ with a static data-dependency graph $G$ on a (parallel) computer. In particular, the parallel black pebbling game has been used as a tool to quantify the (in)security of Data-Independent Memory-Hard Functions (iMHFs). However, the classical black pebbling game is not suitable to analyze the cost of...

Sharding is a critical technique that enhances the scalability of blockchain technology. However, existing protocols often assume adversarial nodes in a general term without considering the different types of attacks, which limits transaction throughput at runtime because attacks on liveness could be mitigated. There have been attempts to increase transaction throughput by separately handling the attacks; however, they have security vulnerabilities. This paper introduces Reticulum, a novel...

Physical attacks pose a substantial threat to the secure implementation of cryptographic algorithms. While considerable research efforts are dedicated to protecting against passive physical attacks (e.g., side-channel analysis (SCA)), the landscape of protection against other types of physical attacks remains a challenge. Fault attacks (FA), though attracting growing attention in research, still lack the prevalence of provably secure designs when compared to SCA. The realm of combined...

Threshold variants of the Schnorr signature scheme have recently been at the center of attention due to their applications to cryptocurrencies. However, existing constructions for threshold Schnorr signatures among a set of $n$ parties with corruption threshold $t_c$ suffer from at least one of the following drawbacks: (i) security only against static (i.e., non-adaptive) adversaries, (ii) cubic or higher communication cost to generate a single signature, (iii) strong synchrony assumptions...

Vehicle-to-grid (V2G) provides effective charging services, allows bidirectional energy communication between the power grid and electric vehicle (EV), and reduces environmental pollution and energy crises. Recently, Sungjin Yu et al. proposed a PUF-based, robust, and anonymous authentication and key establishment scheme for V2G networks. In this paper, we show that the proposed protocol does not provide user anonymity and is vulnerable to tracing attack. We also found their scheme is...

Decentralized Storage Networks (DSNs) represent a paradigm shift in data storage methodology, distributing and housing data across multiple network nodes rather than relying on a centralized server or data center architecture. The fundamental objective of DSNs is to enhance security, reinforce reliability, and mitigate censorship risks by eliminating a single point of failure. Leveraging blockchain technology for functions such as access control, ownership validation, and transaction...

Additive randomized encodings (ARE), introduced by Halevi, Ishai, Kushilevitz, and Rabin (CRYPTO 2023), reduce the computation of a k-party function $f (x_1, . . . , x_k )$ to locally computing encodings $\hat{x}_i$ of each input xi and then adding them together over some Abelian group into an output encoding $\hat{y} = ∑ \hat{x}_i$, which reveals nothing but the result. In robust ARE (RARE) the sum of any subset of $\hat{x}_i$, reveals only the residual function obtained by restricting the...

Fault injection attacks are a serious threat to system security, enabling attackers to bypass protection mechanisms or access sensitive information. To evaluate the robustness of CPU-based systems against these attacks, it is essential to analyze the consequences of the fault propagation resulting from the complex interplay between the software and the processor. However, current formal methodologies combining hardware and software face scalability issues due to the monolithic approach...

We construct pseudorandom error-correcting codes (or simply pseudorandom codes), which are error-correcting codes with the property that any polynomial number of codewords are pseudorandom to any computationally-bounded adversary. Efficient decoding of corrupted codewords is possible with the help of a decoding key. We build pseudorandom codes that are robust to substitution and deletion errors, where pseudorandomness rests on standard cryptographic assumptions. Specifically,...

We continue the study of blockcipher-based (tweakable) correlation robust hash functions, which are central building blocks of circuit garbling and oblivious-transfer extension schemes. Motivated by Roy (CRYPTO 2022), we first enhance the multi-user tweakable correlation robust notion of Guo et al. (CRYPTO 2020) with a {\it key leaking oracle} that tells the adversary whether a certain user key satisfies the adversarially-chosen predicate. We then investigate the state-of-the-art hash...

Garbled Circuit (GC) techniques usually work with Boolean circuits. Despite intense interest, efficient arithmetic generalizations of GC were only known from heavy assumptions, such as LWE. We construct arithmetic garbled circuits from circular correlation robust hashes, the assumption underlying the celebrated Free XOR garbling technique. Let $\lambda$ denote a computational security parameter, and consider the integers $\mathbb{Z}_m$ for any $m \geq 2$. Let $\ell = \lceil \log_2 m...

Although having been popular for a long time, Byzantine Fault Tolerance (BFT) consensus under the partially-synchronous network is denounced to be inefficient or even infeasible in recent years, which calls for a more robust asynchronous consensus. On the other hand, almost all the existing asynchronous consensus are too complicated to understand and even suffer from the termination problem. Motivated by the above problems, we propose SimpleFT in this paper, which is a simple asynchronous...

The conversion between arithmetic and Boolean masking representations (A2B \& B2A) is a crucial component for side-channel resistant implementations of lattice-based (post-quantum) cryptography. In this paper, we first propose novel $d$-order algorithms for the secure addition (SecADDChain$_q$) and B2A (B2X2A). Our secure adder is well-suited for repeated ('chained') executions, achieved through an improved method for repeated masked modular reduction. The optimized B2X2A gadget removes a...

Post-quantum digital signature schemes have recently received increased attention due to the NIST standardization project for additional signatures. MPC-in-the-Head and VOLE-in-the-Head are general techniques for constructing such signatures from zero-knowledge proof systems. A common theme between the two is an all-but-one vector commitment scheme which internally uses GGM trees. This primitive is responsible for a significant part of the computational time during signing and...

Federated Learning (FL) accomplishes collaborative model training without the need to share local training data. However, existing FL aggregation approaches suffer from inefficiency, privacy vulnerabilities, and neglect of poisoning attacks, severely impacting the overall performance and reliability of model training. In order to address these challenges, we propose SuperFL, an efficient two-server aggregation scheme that is both privacy preserving and secure against poisoning attacks. The...

Secure Multi-Party Computation (MPC) constructions typically allow computation over a finite field or ring. While useful for many applications, certain real-world applications require the usage of decimal numbers. While it is possible to emulate floating-point operations in MPC, fixed-point computation has gained more traction in the practical space due to its simplicity and efficient realizations. Even so, current protocols for fixed-point MPC still require computing a secure truncation...

We show that the authentication scheme [Comput. Networks, 225 (2023), 109664] is flawed. (1) Some parameters are not specified. (2) Some computations are inconsistent. (3) It falsely require the control gateway to share its private key with the medical expert. (4) The scheme fails to keep user anonymity, not as claimed.

Fuzzy extractors derive stable keys from noisy sources non-interactively (Dodis et al., SIAM Journal of Computing 2008). Since their introduction, research has focused on two tasks: 1) showing security for as many distributions as possible and 2) providing stronger security guarantees including allowing one to enroll the same value multiple times (reusability), security against an active attacker (robustness), and preventing leakage about the enrolled value (privacy). Existing constructions...

Key Encapsulation Mechanisms (KEMs) are a critical building block for hybrid encryption and modern security protocols, notably in the post-quantum setting. Given the asymmetric public key of a recipient, the primitive establishes a shared secret key between sender and recipient. In recent years, a large number of abstract designs and concrete implementations of KEMs have been proposed, e.g., in the context of the NIST process for post-quantum primitives. In this work, we (i)...

This work investigates the security of the Ascon authenticated encryption scheme in the context of fault attacks, with a specific focus on Differential Fault Analysis (DFA). Motivated by the growing significance of lightweight cryptographic solutions, particularly Ascon, we explore potential vulnerabilities in its design using DFA. By employing a novel approach that combines faulty forgery in the decryption query under two distinct fault models, leveraging bit-flip faults in the first phase...

We introduce protocols for classical verification of quantum depth (CVQD). These protocols enable a classical verifier to differentiate between devices of varying quantum circuit depths, even in the presence of classical computation. The goal is to demonstrate that a classical verifier can reject a device with a quantum circuit depth of no more than $d$, even if the prover employs additional polynomial-time classical computation to deceive. Conversely, the verifier accepts a device with a...

Vehicle Ad Hoc Networks (VANETs) play a pivotal role in intelligent transportation systems, offering dynamic communication between vehicles, Road Side Units (RSUs), and the internet. Given the open-access nature of VANETs and the associated threats, such as impersonation and privacy violations, ensuring the security of these communications is of utmost importance. This paper presents the Identity-based Cluster Authentication and Key Exchange (ID-CAKE) scheme, a new approach to address...

Motivated by the violation of two fundamental assumptions in secure communication - receiver-privacy and sender-freedom - by a certain entity referred to as ``the dictator'', Persiano et al. introduced the concept of Anamorphic Encryption (AME) for public key cryptosystems (EUROCRYPT 2022). Specifically, they presented receiver/sender-AME, directly tailored to scenarios where receiver privacy and sender freedom assumptions are compromised, respectively. In receiver-AME, entities share a...

DCT is a beyond-birthday-bound~(BBB) deterministic authenticated encryption~(DAE) mode proposed by Forler et al. in ACISP 2016, ensuring integrity by redundancy. The instantiation of DCT employs the BRW polynomial, which is more efficient than the usual polynomial in GCM by reducing half of the multiplication operations. However, we show that DCT suffers from a small stretch problem similar to GCM. When the stretch length $\tau$ is small, choosing a special $m$-block message, we can reduce...

Privacy enhancing technologies must not only protect sensitive data in-transit, but also locally at-rest. For example, anonymity networks hide the sender and/or recipient of a message from network adversaries. However, if a participating device is physically captured, its owner can be pressured to give access to the stored conversations. Therefore, client software should allow the user to plausibly deny the existence of meaningful data. Since biometrics can be collected without consent and...

This paper examines the vulnerabilities inherent in prevailing Public Key Infrastructure (PKI) systems reliant on centralized Certificate Authorities (CAs), wherein a compromise of the CA introduces risks to the integrity of public key management. We present PKChain, a decentralized and compromise-tolerant public key management system built on blockchain technology, offering transparent, tamper-resistant, and verifiable services for key operations such as registration, update, query,...

We introduce a new cryptographic primitive, called Completely Anonymous Signed Encryption (CASE). CASE is a public-key authenticated encryption primitive, that offers anonymity for senders as well as receivers. A "case-packet" should appear, without a (decryption) key for opening it, to be a blackbox that reveals no information at all about its contents. To decase a case-packet fully - so that the message is retrieved and authenticated - a verifcation key is also required. Defining security...