International Association
for Cryptologic Research

When estimating the decryption failure rate (DFR) of structured lattice-based cryptography, some schemes implicitly assume that the coefficients of the decryption noise are independent. In practice, however, the decryption noise typically contains terms arising from convolutions of small polynomials, which introduce correlations among coefficients. These correlations can create a non-negligible gap between independence-based estimates and empirical failure rates, leading to underestimated DFRs, overestimated security levels, and exploitable attack surfaces. They also obscure the effect of error-correcting mechanisms in structured lattice-based encryption designs. To date, there has been no practical framework for characterizing such correlations.

In this paper, we give the first systematic characterization of correlations among the coefficients of convolved polynomials with Gaussian coefficients, using the canonical embedding as the central viewpoint. We establish large-deviation results for the coefficients of the resulting polynomial. Our analysis shows that, as the norm grows, convolutional polynomials asymptotically concentrate near a finite set of fixed two-dimensional planes. This gives rise to directional tail structures in the n-dimensional joint probability density, which we call thorns.

As a direct application, we prove that existing decryption-failure attacks succeed precisely by forcing the noise to lie on these thorns. This phenomenon endows the noise with extremely strong correlations, ultimately triggering decryption failures. Furthermore, adopting the canonical embedding perspective allows us to comprehensively illustrate how the independence assumption distorts the true noise distribution. We prove that the independence assumption systematically underestimates the noise norm, and we derive an analytic expression for the probability density function of the Euclidean norm of the decryption noise.

A UOV public key hides a distinguished linear subspace: the public-coordinate image of the central oil-coordinate subspace. In central coordinates, the homogeneous quadratic part of each UOV polynomial contains no oil-oil monomials. Consequently, for every honestly generated UOV public key, each public homogeneous quadratic form vanishes when restricted to this hidden oil subspace. We formalize the hidden oil-subspace relation and construct a Schnorr-like Sigma protocol that proves knowledge of such a subspace without revealing it. The witness consists of matrices $B,W$ satisfying $WB=I_o$ and $Q_k(Bz)\equiv 0$ for all public quadratic forms $Q_k$. The prover masks the witness linearly and responds to a challenge $c$ with $Z=A+cB$, $Y=E+cW$, yielding a protocol with computational 3-special soundness and computational honest-verifier zero knowledge. We prove a generic uniqueness theorem: in the random homogeneous UOV model, the hidden oil subspace is, with overwhelming probability, the unique $o$-dimensional common zero subspace. The uniqueness bound is explicit and negligible for UOV-type parameters. This strengthens the interpretation of the protocol as proving knowledge of the unique hidden oil subspace, rather than merely some oil-like subspace. We provide empirical observations on small parameters and discuss applications and limitations.

The Message Queuing Telemetry Transport (MQTT) protocol is highly preferable for Internet of Things (IoT) environments due to its lightweight architecture, but routing sensitive medical data through a central broker introduces severe privacy risks if the broker is untrusted or compromised. To address this, we propose secure MQTT, a high performance end to end encrypted (E2EE) protocol tailored for constrained devices that renders the broker completely blind to message payloads and incapable of man in the middle (MitM) attacks. Our design utilizes a nested AES-GCM encryption architecture that strictly separates link-level routing metadata from application layer confidentiality. To establish these secure channels efficiently, MQTT integrates MQTT v5.0 enhanced authentication key exchange mechanism via a challenge response embedding one time Broker Nonce into the Schnorr digital signatures version of HMQV key exchange protocol. This provide authenticated end to end session key derivation, that requires only a negligible computational increase over basic ECDH. The security of this proposed model has been rigorously proven using the ProVerif cryptographic verifier under the Dolev-Yao threat model, offering a highly secure, low overhead solution for modern IoT networks.

Li et al. (IEEE Transactions on Dependable and Secure Computing 2026) proposed proxy-free public key authenticated encryption with ciphertext update and keyword search (proxy-free PAUKS). In this short note, we demonstrate that keyword information is leaked from updated ciphertexts. We also demonstrate that our attack is effective against the PAUKS scheme proposed by Li et al. (IEEE Transactions on Information Forensics and Security 2023).

We present a novel construction that applies the Ciphertext-Policy Attribute-Based Encryption paradigm in an original symmetric framework, where also the encryptor needs to have enough attributes to be able to produce a ciphertext for a given policy.

The scheme is built from minimal assumptions on collision-resistant hash functions and pseudorandom functions, exploiting the properties of linear secret sharing and polynomial interpolation. Thus, it is natively Post-Quantum secure.

We formally define a novel extended form for access trees, that trades a polynomial space expansion for a more predictable topological structure. This structure enhance the arithmetic possibilities of the associated secret sharing primitive. Moreover, we propose a comprehensive notation for access trees, sharing and interpolation, which may help in the study of these powerful primitives.

This literature review explores the state-of-the-art advancements in quantum and post-quantum blockchain. The realm of quantum computing is on the rise and will disrupt entire tech industries, including classical cryptography, which is the foundation of blockchain. There has been extensive research on classical cryptosystems (i.e., post-quantum) and their integration with blockchain to create quantum-resistant classical blockchains. We have reviewed the state-of-the-art in these post-quantum blockchains in academic research. But to have forward compatibility with the quantum internet and infrastructure in the future and to have quantum mechanical security, research has been conducted to implement blockchain on quantum technologies and quantum cryptography as well. Consequently, we have explored the current state of research in these quantum solutions, known as quantum blockchains.

We present a method for secure pattern matching over encrypted texts using TFHE. Our approach realizes a fully secure binary search algorithm by leveraging two operational modes of integer-input TFHE. While the BGV-based method of Bonte and Iliashenko (CCSW '20) requires $O(|P| \cdot |T|)$ secure character comparisons to find a pattern $P$ in a text $T$, our method reduces this to $O(|P|\log |T|)$ comparisons, achieving improved scalability for large texts. As a result, our method can find a pattern of length 100 in an encrypted text containing genomic data of one million characters in less than 5 minutes, where prior work would require approximately 5 days for the same task. These results highlight the practicality of TFHE and its potential for large-scale secure string search.

Cheng and Meng (IEEE Transactions on Information Forensics and Security 2024) introduced server-aided public key authenticated encryption with keyword search (SA-PAEKS). In this short note, we give general attacks that the cloud server (tester) can obtain keyword information from both a ciphertext and a trapdoor.

Updatable public-key encryption (UPKE) is a cryptographic primitive that was proposed for secure messaging to provide forward secrecy in public-key settings. It extends standard public-key encryption with a key-update mechanism that lets anyone update a receiver’s public key and issue a corresponding token for updating the secret key. Unlike traditional forward secrecy where all past messages should remain secure after a key leakage, UPKEs guarantee security only as long as at least one honest update has occurred. While classically-secure efficient instantiations of UPKE are known from Diffie-Hellman assumptions, constructing an \emph{efficient post-quantum secure} UPKE scheme with \emph{unbounded} updates remains an open problem. In this work, we propose an isogeny-based UPKE that relies on a dimension-four version of the FESTA public-key encryption scheme. It is practically efficient and supports an unbounded amount of updates. Moreover, we provide a formal security proof based on a problem in isogeny-based cryptography that has received considerable scrutiny.

Active weighted threshold signatures support dynamic changes to signer weights, thresholds, and committee membership. We show that local validity of weighted update operations is not a compositional security abstraction: a sequence of individually valid updates can move an initially sub-threshold coalition into an authorized reachable state. We introduce rank-exposure guards, a compiler that enforces a reconstruction-safety invariant over live, stale, derivative, public, and transient signing material. The compiler wraps ledger-sound one-step update engines with atomic activation and old-epoch digest-bound transition certificates, lifting fixed-state weighted unforgeability and update soundness to sequence-level active unforgeability. We instantiate the compiler as REG-ADAPT, a guarded GLI reconfiguration scheme built around ADAPT-style local updates, and implement it on top of the public ADAPT Go artifact. Our evaluation shows that the artifact detects and rejects unsafe update sequences, while adding only microsecond-scale metadata and rank-audit overhead.

The only known solution to the big APN problem was found by exploring the CCZ-equivalence class of a specific quadratic function, the Kim mapping, which is linearly equivalent to various highly-structured functions. For example, one of these functions has a univariate representation with a specific factorisation highlighting its subspace property and that it is a cyclotomic mapping, while another has a bivariate representation corresponding to a $(q,q)$-projective mapping.

In this paper, we show that the properties of this kind all correspond to a type of functions we introduce: multivariate projective mappings. These are multivariate functions whose coordinates are homogeneous. Furthermore, while a function might not have this form, it can still be equivalent to another function that has it. To handle this case, we describe how to identify the presence of a multivariate projective mapping in the linear-equivalence class of a function. We then derive our main result: for almost all known infinite families of APN functions, there exists a multivariate projective mapping, or a function commuting with the Frobenius mapping, that is CCZ-equivalent to them. Despite the widely different initial representations of these families (univariate, bivariate, or trivariate), this pattern holds. We also discuss concrete techniques to detect (or rule out) the presence of a multivariate projective mapping equivalent to a given function.

Research on cryptographic algorithms implemented in hardware and protected against side-channel attacks has advanced rapidly in recent years. Generalized masking schemes, such as Threshold Implementations (TI) and Domain-Oriented Masking (DOM), currently provide a solid theoretical security foundation. Security models, including the probing model and its various extensions, enable formal verification of these guarantees. In addition, established guidelines for designing securely composable gadgets, along with tools for the automatic generation of masked designs, have further advanced the field. Experimental security assessment approaches, such as the Test Vector Leakage Assessment (TVLA) complement these efforts. Consequently, the primary focus of the research community has shifted toward optimizing existing techniques and bridging the gap between theoretical and practical security models.

In this work, we demonstrate a case in which side-channel leakage, caused by glitches, can be concealed during experimental assessment in a setup that is theoretically not robustly secure. This effect arises due to specific patterns of glitch propagation. We investigate whether a particular layout of the complete logic chain can further contribute to a design’s resistance to side-channel attacks, potentially reducing latency and area by relaxing glitch-mitigation requirements, such as reducing the number of pipeline registers. To this end, we introduce new adversarial model which further relaxes the model of Müller and Moradi, introduced at CHES 2024. To illustrate the practical relevance of our proposal, we provide experimental evidence by modifying a well-known, provably secure AES S-box design by De Cnudde, rendering it insecure under the robust probing model. We conduct TVLA of power consumption for both FPGA-based (physical) and ASIC-like (simulation) implementations of our netlists, demonstrating the absence of detectable leakage, similar to the originally robustly secure version of the algorithm.

End-to-end encrypted (E2EE) messengers such as Signal, WhatsApp and iMessage increasingly deploy Key Transparency (KT) to make malicious key substitution detectable. Yet KT only delivers its intended protection if users are anchored to the same global append-only KT history. A malicious operator can break this condition by equivocating, presenting incompatible views of the KT directory to different clients. Current deployments delegate detection to a small set of third-party auditors, creating a centralized trust bottleneck that can be pressured, compromised, or fail to audit continuously.

We ask whether clients can detect equivocation themselves, without dedicated infrastructure, simply by comparing KT state as they communicate. We introduce MINGLE, an opportunistic in-band gossip protocol for end-to-end encrypted messengers. MINGLE piggybacks compact KT commitments on a subset of ordinary messages before encryption, keeping gossip indistinguishable from regular application data while requiring no external services or overlay network. Rather than asking users to manually verify safety numbers or relying on a small set of auditors, MINGLE distributes the consistency check across the entire communication graph: an adversary wishing to sustain a split view must permanently isolate targeted clients from the rest of the network, preventing any cross-partition message from ever being delivered, a requirement that grows increasingly difficult to maintain covertly as the social graph densifies. MINGLE inherits the Trust-on-First-Use (TOFU) assumption standard in E2EE messengers: equivocation that begins at registration evades immediate detection, though the append-only log ensures it remains retroactively exposable once any cross-partition gossip event occurs. Using a temporal communication model, we show that under eventual cross-partition connectivity, conflicting KT views yield publicly verifiable evidence.

We prototype MINGLE in the Signal Android client using Signal's KT Server implementation, incurring a payload overhead of 119 bytes per gossip-carrying message without UI changes. Simulations under realistic messaging patterns show that MINGLE achieves high reliability and fast evidence generation without aggressive gossip flooding. MINGLE yields evidence of a targeted split view in a \(12000\)-client deployment within about \(5\) minutes when only \(20\%\) of clients participate and gossip is attached to roughly \(5\%\) of messages, suggesting that ordinary client communication can serve as a practical audit layer for KT.

Publicly Verifiable Secret Sharing (PVSS) is widely used in distributed systems. Existing schemes usually incur at least $O(n)$ online cost: the dealer encrypts, proves, and publishes $n$ shareholder-dependent objects, which public verification must process. In this work, we present a generic framework that transforms publicly verifiable CCA2-secure threshold encryption (CCATE) into \emph{constant-online} PVSS, with distribution and public- verification costs independent of the number of shareholders. The framework moves the share-generation work into a reusable setup phase: once threshold keys and public verification material are fixed, online sharing amounts to a single publicly verifiable threshold encryption. We instantiate the framework with two CCATE constructions: 1) a pairing-free instantiation using standard Threshold ElGamal encryption under a committee-based setup assumption; and 2) a silent-setup scheme leveraging non-interactive key generation via a Power-of-Tau ceremony, eliminating inter-party coordination during setup. Furthermore, we discuss epoch-based membership updates under the corresponding setup assumptions, clarifying the security boundary of reconfiguration. The resulting schemes incur higher setup costs, but the critical online distribution and public-verification phases are constant-size and constant-time. This trade-off is particularly useful when setup can be amortized over many PVSS instances, as in blockchain and distributed-system deployments.

Efficient and secure hardware implementations of post-quantum cryptographic schemes are critical for real-world adoption. In this work, we propose a unified FPGA-based architecture for Kyber and Dilithium that combines flexibility, lightweight design, and fault tolerance. The architecture adopts a microcoded, programmable datapath supporting both schemes with minimal area overhead, enabling seamless integration of modules such as SHAKE, sampling, and coefficient rounding. To enhance resilience against propagation-based fault attacks—which exploit effective/ineffective fault behavior in public-domain computations—we embed a probabilistic verification mechanism using rejection sampling. This countermeasure transforms deterministic operations into cryptographically constrained probabilistic processes that remain efficient under normal conditions while significantly degrading under adversarial faults. The result is a robust and compact design that not only supports both a lattice-based KEM and signature scheme, but also provides the first unified fault countermeasure architecture for Kyber and Dilithium, maintaining low retry counts and minimal performance degradation in fault-free environments.

The advent of quantum computing is expected to transform the landscape of cryptographic security, making many classical algorithms vulnerable to quantum attacks such as Grover’s exhaustive key search. In this study, we present an efficient quantum circuit implementation of the lightweight block cipher KLEIN for all variants. Each functional component of the cipher, such as key addition, substitution, RotateNibbles, MixNibbles, and key scheduling, is implemented. The complete quantum design involves gates such as CCNOT, CNOT, and Pauli-X. Furthermore, we provide a comprehensive resource estimate for executing Grover’s search algorithm on the proposed quantum circuits, highlighting their resilience and practicality in post-quantum cryptographic contexts.

Research at the intersection of artificial intelligence (AI) and cryptography is expanding, but existing surveys often focus on specific techniques or provide only high-level overviews without cross-domain comparison. This paper presents a trend analysis across major subfields of AI-aided cryptography. We review 90 publications from 2021–2025 and complement them with call for papers from journals, conferences, and public tenders. The results show uneven coverage: cryptanalysis and hashing dominate, while protocols, encryption, and post-quantum cryptography are less explored. We outline emerging gaps and likely growth areas to support future research prioritization.

Trusted Execution Environments (TEEs), also known as secure enclaves, such as Intel SGX, Intel TDX or AMD SEV are seeing widespread use to perform computations on highly sensitive data. To analyze the security of cryptographic protocols using TEEs, several formal models exist, notably the one by Pass et al. (EUROCRYPT 2017) for attested computations in the Generalized UC framework. Using this model and the proposed global ideal functionality $\mathcal{G}_{\mathrm{att}}^{\mathrm{PST}}$, provably secure multi-party computations with practical efficiency are possible. Attested computations are achieved by having enclave outputs signed with a key pair held by $\mathcal{G}_{\mathrm{att}}^{\mathrm{PST}}$, together with the enclave's code. Being a global functionality, the verification key can be obtained by any party. Perhaps surprisingly, this model does not give rise to a meaningful notion of public verifiability, i. e. the ability of external parties to plausibly verify results, even though some commercially available enclaves allow exactly that. We formalize this intuition in the form of an impossibility result and propose a novel simulation technique where equivocation is not handled by the simulator resp. adversary anymore, but in a coordinated effort between our new functionality $\mathcal{G}_{\mathrm{att}}$ and a (local) ideal functionality $\mathcal{F}$ that is realized with public verifiability. To this end, several technical problems need to be solved, in particular to ensure that this new mechanism cannot be abused. While unconventional, this approach is, to the best of our knowledge, the first to achieve a general variant of public verifiability a) even when all protocol parties are corrupted and $\mathcal{F}$ is probabilistic and b) where guarantees of honest (external) verifiers are not affected by simulation at all. We call the latter property global public verifiability. We also address a second impossibility result of Pass et al., namely the requirement that every protocol party needs a TEE (even in a setting without public verifiability), unless an additional (global) setup is used. We address this impossibility result by introducing designated-verifier attestations that are only valid for a single party in a single protocol execution, akin to what is possible with real-world enclaves. Using our improved model, we propose protocols for (globally publicly verifiable) composable general MPC and prove their security under the notion of Universal Composition with Global Subroutines (Badertscher et al., TCC 2020) and static malicious corruptions.

Fair and free elections are the foundation of democracies and democratic processes. They require voting protocols that guarantee the integrity and verifiability of the result, as well as the private choice of each voter. Currently deployed e-voting protocols rely on traditional hardness assumptions, like the discrete logarithm problem, to provide these security guarantees. They are not post-quantum secure (pq-secure). While first proposals for pq-secure protocols exist, they are limited in the variety of voting scenarios they can support and/or in terms of efficiency.

In this work, we therefore propose PQKryvos, an efficient and flexible pq-secure homomorphic e-voting protocol that can be instantiated for a wide variety of election methods and ballot formats. Our construction efficiently combines homomorphic lattice-based commitments with hash-based general-purpose proofs (GPZKPs) to ensure ballot correctness. As a pq-secure instantiation of the Kryvos framework introduced by Huber et al. (CCS 2022), PQKryvos not only provides voter privacy and (public) verifiability of the result, but additionally allows for the stronger privacy notion of public tally-hiding. Public tally-hiding ensures that only the intended election result (such as the full vote count or only the winner) is publicly revealed, while no additional information is leaked. This further improves the privacy for both voters and election candidates.

PQKryvos is the first homomorphic pq-secure e-voting protocol to generically support arbitrary ballot formats and the first to provide public tally-hiding. Our implementation and evaluation of PQKryvos demonstrate that it achieves practical performance for diverse election schemes and outperforms the original pre-quantum Kryvos instantiation in some settings. Moreover, we demonstrate that by utilizing GPZKPs, existing pq-secure e-voting protocols can support additional ballot formats, can be enhanced in their tallying phase, and can be extended to publicly tally-hiding protocols.

Blockchain-enabled data sharing provides public verifiability and auditability for access control in Internet of Things environments. However, before formal authorization is granted, efficiently verifying whether a data requester satisfies a hidden access policy remains challenging. Existing schemes may expose user attributes, access policies, or matching relationships during on-chain verification, while pairing-based operations, decryption tests, or general zero-knowledge circuits often introduce high verification overhead or strong trust assumptions.

To address these issues, this paper proposes a privacy-preserving pre-verification access control scheme based on attribute vector commitments and Bulletproofs. The proposed scheme encodes user attributes and access policies into vector forms and uses vector commitments to hide authenticated user attributes. Access eligibility verification is then transformed into a hidden inner-product relation, allowing a data requester to prove policy satisfaction without revealing its real attributes or the policy contents. The pre-verification process is pairing-free and does not require trusted setup, making it suitable for smart-contract-based public verification. In addition, proxy re-encryption is integrated to support controlled data access after successful pre-verification.

Security analysis shows that the proposed scheme achieves pre-verification completeness, knowledge soundness, zero-knowledge, attribute privacy, policy privacy, and collusion resistance. Performance analysis and experimental results demonstrate that the proposed scheme reduces on-chain verification overhead, communication cost, and deployment complexity compared with existing access control schemes, making it practical for privacy-preserving data sharing in blockchain-assisted Internet of Things environments.