International Association
for Cryptologic Research

We prove the existence of succinct arguments for QMA, assuming only the existence of collapsing hash functions. This is the first scheme that relies only on unstructured ``Minicrypt'' assumptions, which are not known to imply public-key encryption.

Our main technical contribution is a quantum-succinct claw-state generation protocol that allows us to bootstrap a small number of quantum correlations into an arbitrarily large number of claw-state correlations, using classical communication only. This improves upon the work of [Zhang, STOC 2021], having better round complexity, a proof in the standard model, and being overall much simpler. This yields a quantum-succinct blind delegation of quantum computation protocol from one-way functions, which we plug into the communication-compression compiler of [Bartusek, Liu, and Malavolta, EUROCRYPT 2026] to obtain succinct arguments for QMA.

Tools for generating deep fake photographs are proliferating with greater ease of use and prominence in pop culture. Image authentication tools can defeat these deceitful developments by verifying that a digital image was actually produced by a physical camera. The challenge is that these tools must be robust to desirable image transformations.

Camera attestation uses digital signatures to prove an image's provenance from a camera. Lossy compression makes minute changes in order to reduce an image's size, and blurring or redacting regions of an image can protect its subjects. These changes invalidate an image's signature. Prior works use zero-knowledge (ZK) to prove a published image's edit history, but they do not survive lossy encoding such as the JPEG format.

We present \zkjpeg, a cryptographic tool for JPEG compression that proves an image was correctly compressed from a secret, committed input. In addition, our tool can verify a large family of image transformations by integrating them into JPEG compression with minimal cost.

Our system is fast, flexible, and can be instantiated from off-the-shelf ZK tools. We use PicoZK to convert Python image editing code into a ZK circuit for the line-point zero knowledge (LPZK) proof system.

Lightning's BOLT 12 (offers, onion messages, blinded paths) is the largest addition to the Lightning protocol suite, and it is rolling out now. The specification changed three times in 2026, the community is actively debating its privacy posture, and its newest mechanism, Payer Proofs, landed in July 2026 without any analysis. We give the offer family its first formal treatment, covering the full lifecycle from request to receipt, pinned to specification commits e20a924/1528972 and machine-checked in twenty-two ProVerif models that each converge within seconds. The results read as a map rather than a checklist: the family's privacy and integrity rest on seven bindings, removable assumptions whose removal consequences we check row by row. Receiver anonymity and payer-payee unlinkability hold under unbounded sessions and corrupted path nodes, and every protocol-level attack we exhibit lands on an assumption the specification already leans on out-of-band. The map's structure is itself the finding. The blinding key chain, designed for unlinkability, authenticates recipient-side transit for free, while the payer side's delivery binding rests on implementation discipline alone. The newest part of the specification, its payment receipts, turns out to hide a precise disclosure boundary. We close with six testable recommendations for the BOLTs repository.

Silent payments (BIP-352) let Bitcoin users publish one static address and receive at fresh, unlinkable outputs. The protocol already ships in major wallets, yet its own specification concedes it has no formal security proof—and 2026 brought a worst-case scanning attack, a funds-locking hardware-wallet disclosure, and an omitted-payment bug. We supply the missing analysis. Receiver and co-transactor unlinkability are proved under DDH, with the label system as a corollary that includes an executable linking attack and its fix. We then quantify what scanning costs and what an attacker can buy with it. The community's K_max cap turns quadratic attack amplification into linear; every compliant scanner needs Ω(N+KM) work; our set-probing scanner meets this bound and runs 39× faster in our measurements; and a year of fee data prices a full-block attack as low as 0.0015 BTC. For collaborative transactions we show what the specification's warning was about (the transaction assembler can always identify the recipient's output, and malformed partial secrets burn payer funds, the failure class disclosed in August 2026), and we construct the variant the warning called for: blind collaborative payments with information-theoretic payer privacy. Delegation, finally, offers no safe default: scanning servers either learn too much or can hide payments. A twelve-experiment benchmark suite accompanies the paper.

The 5G-Advanced air interface is acquiring its first AI-native functions (AI/ML-based CSI feedback compression and beam management, studied by 3GPP since Release 18) and their models increasingly arrive through third-party supply chains. We present the first cross-use-case backdoor study of this interface. Poisoning as little as 0.5% of the training data implants an arbitrary trigger-to-target association into CRNet (and, at 5% poisoning, into CsiNet): attack success is 100% with no measurable clean cost, with physical triggers so weak that a 2-bit RIS suffices to launch them. The same trigger and pipeline hijack a second standardized function, beam prediction, with 99.5% success. Hijacked feedback steers gNB beamforming toward a phantom channel: a victim's rate falls by 98%, and the diverted beam concentrates 88% of the array-gain ceiling onto the attacker, raising interception probability to 100%. An adaptive attack that matches codeword statistics drives both statistical detectors from ≈1.0 to 0.53 AUC with attack strength unchanged, yet behavioral consistency still detects it: codewords can be disguised, behavior cannot.

Private Set Intersection (PSI) enables two parties to compute the intersection of their private sets without revealing any additional information. For plain PSI, there exist extremely efficient solutions based on symmetric-key techniques for both the semi-honest and malicious settings. However, for more enriched set operations such as PSI-Cardinality, PSI-Sum, Circuit-PSI, and Private Set Union, the efficiency gap between the semi-honest and malicious settings is significant, often spanning orders of magnitude. A key bottleneck underlying these protocols is the need for a shuffled distributed oblivious pseudorandom function (SH-DOPRF) with malicious security. Existing constructions for this primitive are asympotically suboptimal and/or concretely inefficient. In this work, we present a new protocol for SH-DOPRF with malicious security that achieves linear computation and communication complexity. We present two instantiations: a DDH-based construction using the Dodis-Yampolskiy PRF (PKC 2005), and a plausibly post-quantum secure construction based on a variant of the Dark-Matter PRF (Aranha et al., S&P 2026). Our approach is almost entirely based on symmetric-key techniques, with public-key operations used only for evaluating PRF outputs. This primitive yields maliciously secure protocols for multi-query reverse private membership test (Zhang et al., USENIX Security 2023), which in turn can be used to realize the aforementioned private set operations. These protocols provide two-sided outputs while only additionally leaking the cardinality of the intersection. We implement and evaluate our construction to demonstrate concrete efficiency. Our DDH-based maliciously-secure SH-DOPRF achieves a 2--3 orders of magnitude improvement in total running time compared to the state-of-the-art (Miao et al., CRYPTO 2020 & Yang et al., PoPETs 2025), leading to a similar improvement for PSI-Cardinality. The resulting protocols for various other private set operations also achieve significant improvements over prior work; for example, our PSI-Sum and Circuit-PSI protocols are 1--2 orders of magnitude more efficient.

A Private Information Retrieval (PIR) scheme allows a client to retrieve data from a database hosted on a remote server without revealing which location is being accessed. In Doubly-Efficient PIR (DEPIR), the server preprocesses the database offline into a data structure that enables it to answer any client query in sublinear time with respect to the database size $n$. Lin, Mook, and Wichs (STOC 2023) presented the first DEPIR, from RLWE, and Lee (Crypto 2026) gave a barely doubly-efficient scheme from LWE in the CRS model, answering each query in $o(n/\log n)$ time. These are essentially the only constructions known, and both rest on lattices. Whether DEPIR could be realized from non-lattice-based foundations, particularly from number-theoretic assumptions, remained in doubt.

In this work, we construct a DEPIR scheme from quadratic residuosity in the CRS model, answering each query in $o(n/\log n)$ time. As in Lee's LWE-based construction, our scheme leverages Williams's matrix-vector multiplication preprocessing (SODA 2007). Privacy follows from the pseudorandomness of Legendre symbols under quadratic residuosity, proved by Corrigan-Gibbs and Wu (TCC 2025). To cope with a new modulus at every query, we additionally develop a data structure that reduces a preprocessed integer modulo any modulus in sublinear time.

Private Information Retrieval (PIR) allows a client to retrieve an entry from a public database without revealing the entry of interest. Standard PIR, however, requires the server to perform expensive computation that is linear in the database size per client query. To reduce this online cost, Online-Offline PIR (OO-PIR) was proposed, allowing the client to precompute a query-independent hint table that enables sublinear online query complexity. Unfortunately, existing OO-PIR protocols require either a non-colluding two-server setting or a single-server setting with expensive periodic preprocessing, where the entire hint table must be rebuilt after a limited number of online queries. This results in extremely high bandwidth or computation overhead.

We present ESCAPE, a novel OO-PIR protocol for the single-server setting that completely eliminates the expensive periodic preprocessing, supporting unlimited online queries in sublinear time with low constant response bandwidth. The core innovation in ESCAPE lies in reconciling a new hint sampling strategy with Linearly Homomorphic Encryption (LHE) to conceal the correlation between any hint and any online query, while allowing the consumed hint to be refreshed on the fly in sublinear time. We design a random sampling structure that aligns with deterministic, precomputable linear functions, enabling the protocol to exploit the streamlined preprocessing of efficient LHE instantiations. We fully implement ESCAPE, evaluate it on large-scale databases, and release our implementation as open source. Experimental results show that ESCAPE radically reduces end-to-end latency to under a second for 1-8 TiB database sizes and 8-16 KiB entries, achieving up to two orders of magnitude lower bandwidth and up to three orders of magnitude lower computation than state-of-the-art PIR.

We study the optimal dimension-free constant $C_*(a)$ in Talagrand's Boolean convolution inequality $\Pr_\mu[T_af\ge u]\le C_*(a)/(u\sqrt{\log u})$, where $T_a$ is the noise operator, $\mu$ is the uniform measure on the Boolean cube, $f\ge0$ satisfies $\mathbb{E}_\mu[f]=1$, and $u>1$. We establish explicit upper bounds for every $0

The rapid advancement of Zero-Knowledge Proofs (ZKP) has motivated the design of ZK-friendly hash functions. A relatively new design strategy for ZK-friendly hash functions is using the composition of small look-up tables (LUTs) to build a nonlinear transform (called Bars layer) over a large prime field $\mathbb{F}_p$. This not only improves the plain performance but also enhances its security against algebraic attacks since the Bars layer is equivalent to a complex and high-degree polynomial over $\mathbb{F}_p$. This design strategy was first proposed at CCS 2022 for the ZK-friendly hash function Reinforced Concrete. However, there has been no third-party collion attacks of Reinforced Concrete since then, and all existing attacks on such LUT-based ZK-friendly ciphers like Tip5, Monolith and Skyscraper mainly exploit the differential or linear properties of Bars.

In this paper, we demonstrate that the Bars layer surrounded by MDS matrices (called Concrete layers) with small integers, i.e., $Concrete\circ Bars\circ Concrete$, might lead to weaker differential properties of the round function. This key observation leads to a novel collision attack on 4.5 out of 7 rounds of Reinforced Concrete, successfully bypassing the Bars layer as well as the subsequent Concrete layer and power-map-based nonlinear layer (called Bricks layer). The attack is verified by providing a practical collision for 3.5-round Reinforced Concrete where the last 4 layers are $Bricks \circ Concrete \circ Bars\circ Concrete$.

Furthermore, we provide constructive countermeasures by designing an algorithm to generate an improved Concrete layer that thwarts this specific attack while preserving the efficiency of the original design. Finally, we also applied our framework to Tip5 but found that its MDS matrix can effectively prevent this attack. This is the first time to exploit the weak combination of Bars layer and Concrete layer to mount efficient attacks on LUT-based ZK-friendly hash functions. We believe that it sheds new insight into the security of these hash functions.

Pseudorandom correlation functions (PCFs) allow two parties to expand short correlated keys into an unbounded, locally evaluatable source of correlated randomness. In this paper, we give the first constructions of PCFs for correlated oblivious transfer (COT) and vector oblivious linear evaluation (VOLE) correlations over $\mathbb{Z}_M$ for an arbitrary modulus $M$, with reasonable concrete efficiency. Our construction comes with a lightweight, two-round distributed setup protocol, and relies solely on the decisional composite residuosity (DCR) assumption.

As part of our security analysis, we introduce a new family of extended power DDH problems over subgroup indistinguishability groups, and give a novel master theorem showing that this is implied by standard DCR. This suffices to prove security of our PCF based on DCR, and also implies that prior constructions relying on related power-DDH style assumptions in composite groups can be based on DCR alone.

We further extend our construction to obtain a PCF for oblivious linear evaluation (OLE) and general degree-two correlations over $\mathbb{F}_2$.

As an application of our PCF for VOLE, we derive a designated-verifier exponent-verifiable random function (eVRF), where the publicly verifiable output is the VRF output in the exponent. As an independent contribution, we additionally give a publicly verifiable eVRF from an offline/online variant of homomorphic secret sharing. Both of these constructions have much shorter proof sizes than prior work.

Secure multiparty computation (MPC) is a key enabling technology for privacy-preserving applications. To achieve low latency after inputs are provided, many efficient protocols utilize preprocessing, and the landscape of preprocessing approaches is growing and diverse. Some recent works use variants of function-dependent preprocessing, leveraging additional knowledge on the function to be computed for even better performance. While the existing literature primarily focuses on performance, it is mostly overlooked that there exist different kinds of function dependence and what practical implications they have. We systematize the different flavors of function dependence, relating them to practical requirements beyond efficiency.

Theta series are fundamental functions that record lattice-vector lengths and connect lattice geometry with Gaussian quantities such as Gaussian mass and the smoothing parameter. For ideal lattices under the canonical embedding, arithmetic coordinates are generally coupled, making fixed-coset theta-series evaluation and related Gaussian computations difficult in high dimensions. We show that an explicit, verifiable relative-basis condition yields an exact factorization of each fixed-coset theta series into lower-dimensional factors.

For each fixed coset, when n = ℓ n₀, its n-dimensional theta-series computation is replaced by ℓ independent computations in dimension n₀. Equivalently, the canonical Gram matrix is block diagonal in the relative coordinates, and the factorization holds for every Gaussian parameter without approximation or a smoothing assumption. We verify the condition for several cyclotomic and non-cyclotomic extensions and derive explicit formulas for representative cyclotomic families. The same factorization gives lower-dimensional identities for Gaussian masses, independent Gaussian sampling within a fixed coset, and smoothing-parameter equations. It reduces the dimension of each coset calculation, while the outer sum over the residue classes in I_q remains unchanged. Our implementation achieves speedups of up to 335×, 215.45×, and 7.9× for fixed-coset theta-series evaluation, numerical smoothing-parameter evaluation, and sequential Gaussian sampling, respectively.

Updatable Private Set Intersection (UPSI) extends conventional PSI protocols to dynamic scenarios, where input sets evolve over time. A straightforward approach is to rerun the entire PSI protocol after each update, incurring redundant computational and communication overhead. Although several UPSI schemes have been proposed to enable updates without full protocol re-execution, existing constructions remain impractical.

Building on the high efficiency of unbalanced PSI designs, this work introduces Leopard---a general framework that leverages unbalanced PSI to realize UPSI without complete re-execution, while handling both insertions and deletions. Leopard is compatible with any unbalanced PSI protocol and achieves further performance gains by reusing internal data structures across updates. Specifically, we observe that certain data structures in unbalanced PSI can be incrementally updated instead of fully rebuilt. We provide an FHE-based instantiation of Leopard that demonstrates substantial performance improvements through such data structure reuse.

Through comprehensive experiments, we evaluate Leopard's performance. Compared to Badrinarayanan et al. (ASIACRYPT 2024) and Alborch et al. (ACNS 2026), our instantiations reduce computational cost by up to 111.28× and at least 1.48×, and communication cost by up to 118.97× and up to 522.01×, respectively.

The Middle-Product Learning With Errors (MP-LWE) problem, introduced by Roşca, Sakzad, Steinfeld, and Stehlé (Crypto 2017), is a structured variant of LWE defined independently of any specific number field $K$. Its hardness has been based on the hardness of Ring-LWE (RLWE) over families of number fields. Two main reductions exist, one from Roşca, Sakzad, Steinfeld, and Stehlé (Crypto’17) and Njah Nchiwo and Pellet-Mary (PKC’26), and another one due to Peikert and Pepin (Journal of Cryptology’24). Both reductions cover different families of number fields, and none of the two supersedes the other. In this work, we propose a unified reduction from RLWE to MP-LWE parameterized by a pair of field elements $(y_a,y_s) \in K^2$, which recovers both prior reductions as concrete instantiations. Optimizing the choice of $(y_a,y_s)$, we obtain the first reduction from RLWE to MP-LWE that holds for all number fields $K = \mathbb{Q}[X]/f(X)$ where $f$ is a monic irreducible polynomial of a given degree and with polynomially bounded coefficients (and whose discriminant is coprime to the modulus $q$ of the RLWE and MP-LWE problems, a constraint that also appeared in previous works). This new reduction supersedes the two previously known reductions.

Cryptographic combiners take $n$ candidate schemes for some primitive $P$, and realize it securely provided that at least $k$ candidates are secure. Intuitively, we expect that if we plug $n$ independent instances of a $\delta$-weak candidate for $P$ into the combiner, assuming $\delta \ll (n-k)/n$, security should be amplified and the resulting candidate should exhibit a significantly smaller weakness. This intuition relies on the implicit “all-or-nothing” assumption that each candidate fails with probability $\delta$ and is otherwise perfectly secure, allowing us to bound the failure probability of the combiner using a simple binomial tail bound. However, this intuition often fails for standard security notions where, for example, a weak candidate may consistently leak partial information rather than exhibit a clean all-or-nothing failure.

Recently, Applebaum, Bitansky and Geier (CRYPTO 2026) showed that indistinguishability combiners inherently act as security amplifiers. However, this general result incurs a multiplicative loss of roughly $2^{n-k}$ in the error parameter relative to the natural all-or-nothing bound. Moreover, the combiner-is-amplifier approach is fundamentally restricted to the regime $\delta < 0.5$. Consequently, both the resulting error rate and the amplification threshold $\delta_0$ are suboptimal.

In this work, we overcome these limitations by establishing a new specialized framework of bias-resilient indistinguishability combiners. This formulation allows us to achieve the optimal all-or-nothing bound without the exponential penalty. We observe that bias-resilience provides a unifying abstraction for security amplification across different primitives, neatly capturing prior ad hoc results such as those for weak PRGs and weak NIZK.

As our main application, we use this framework to establish a generalized XOR lemma over prime fields $\mathbb{F}_p$, showing that the sum modulo $p$ of independent weakly pseudorandom elements becomes computationally indistinguishable from uniform. This improves upon a recent work by Shimizu and Yasunaga (STOC 2026) by achieving a sample complexity that is independent of the field size.

Finally, we explore the idealized notion of an all-or-nothing amplifier. We establish a tight characterization of the multiplicative penalty incurred when applying such an amplifier to candidate schemes that only guarantee standard weak indistinguishability error.

The latency of sleepy consensus protocols has been improved significantly, with recent designs achieving constant-round confirmation. However, existing protocols either rely on unrealistic additional assumptions about access to historical messages, where messages sent in round $t$ may depend on messages received in rounds $[t-k,t-1]$ for some $k>1$, or do not consider optimizing performance under optimistic conditions.

In this work, we study history-independent sleepy atomic broadcast protocols while simultaneously considering optimistic conditions, where messages sent in round $t$ depend only on messages received in round $t-1$. We first design a sleepy atomic broadcast protocol that achieves a confirmation latency of $2\Delta$ ($\Delta$ is the upper bound on network delay) and an optimal latency of $\Delta$ under up to $1/5$ corruption. Second, we present a super-optimistic atomic broadcast protocol, achieving a best-case latency of $2\Delta$ under fault-free executions. Building on this insight, we propose an optimistic sleepy atomic broadcast protocol that relaxes the super-optimistic condition to tolerate sub-optimal faults. As a building block, we introduce an optimistic graded agreement protocol, $OptimisticGA$, which enables a dynamic optimistic quorum with four decision grades. Built on $OptimisticGA$, our optimistic atomic broadcast protocol achieves a good-case latency of $2\Delta$ when the leader is honest, while tolerating up to $1/6$ corruptions rather than requiring a fault-free setting. When corruption is more than $1/6$, it seamlessly adapts to $1/3$ resilience with a good-case latency of $3\Delta$. All protocols require no historical messages and tolerate an adversary that grows proportionally with honest nodes, with a minimal delay of $\Delta$.

While an abundance of SCA methodologies have arisen over the years with impressive theoretical backgrounds, they fail to take into account some important real-world aspects in the analysis. Most of them fail on three key points. First, most assume IID or normally distributed data points in their framework without verifying that the experimental setup indeed meets that requirement. Second, most methods rely on visual aspects or failed statistical tests to define the success or failure of the tests without quantifying the precision of their measurement with formal boundaries. Third, in most cases, the test harness is not completely oblivious to the secret data, remaining completely free of data-dependent branching, conditional formatting, or conditional triggering, which can leak environmental noise and contaminate the data points. We are proposing a new SCA methodology, which we named BLAQ, to bridge this gap between the theoretical mathematical models and the real-world imperfect testing environment.

Let $\mathrm{MQ}_0(n)$ and $\mathrm{MQ}_1(n)$ be the sets of square systems of $n$ quadratic equations in $n$ variables over $\mathbb{F}_2$ having, respectively, no solution and exactly one solution, and write $\alpha_0=|\mathrm{MQ}_0(n)|$, $\alpha_1=|\mathrm{MQ}_1(n)|$. It is known that $\alpha_0<\alpha_1$, so injections $\mathrm{MQ}_0(n)\hookrightarrow\mathrm{MQ}_1(n)$ exist; the proof is a counting argument and produces no map. We exhibit a partial injection $\tau$, in the following sense. The map $\tau$ adds to a system a single correction supported on an affine flat of codimension two through a point read off by a three-point decoder; it is computable in $\Theta(n^3)$ bit operations from the dense coefficient representation, with no precomputation and no advice. We prove that there is a subset $\mathcal{D}\subseteq\mathrm{MQ}_0(n)$ with $|\mathcal{D}|/|\mathrm{MQ}_0(n)|>0.745$, uniformly in $n\ge3$, on which $\tau$ is injective into $\mathrm{MQ}_1(n)$. We then show that inverting $\tau$ is \emph{equivalent} to locating a zero of the image system --- the solvable case of the multivariate quadratic problem, and its one-solution case on the uniquely solvable part of the image --- and that $\tau$ is randomly self-reducible on each orbit of its symmetry group. Under the standard assumption that solvable $\mathrm{MQ}$ is hard on average --- the planted-$\mathrm{MQ}$ assumption of $\mathrm{MQ}$-based identification and signature schemes --- $\tau$ is therefore a one-way function, injective on $\mathcal{D}$, explicit and randomly self-reducible on each orbit, between two sets which are, as languages, complexity-theoretically far apart. We also show that the associated flat-collision problem is NP-complete.

Distributed randomness beacons enable mutually distrustful parties to jointly generate public randomness. Several existing beacons built from secret sharing use costly pairings or group operations to verify shares. Their underlying discrete-logarithm assumptions are also vulnerable to quantum attacks. Moreover, running a separate Byzantine fault-tolerant (BFT) consensus instance for each output incurs repeated computation and communication costs, even when secrets are shared in batches. We present Silk, a computation-efficient, post-quantum-friendly and deterministic randomness beacon under partial synchrony. Silk's sharing protocol, Mulberry, realizes batched asynchronous verifiable secret sharing with partial output (bAVSS-PO), using hash-based share verification to reduce computation cost. Silk further amortizes BFT consensus across a batch of outputs, requiring only one BFT instance per batch. We establish Mulberry's bAVSS-PO properties and Silk's beacon properties under static corruption and the stated security assumptions. We implement Silk and Mulberry in Rust and evaluate their computation and communication costs. In WAN experiments with 121 replicas across eight AWS regions, Silk achieves a throughput of 5.414 outputs/s, 1.53× that of Rondo [NDSS'25] and 4.18× that of Spurt [IEEE S&P'22].