International Association for Cryptologic Research

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21 April 2026

Fatemeh Khojasteh Dana, Saleh Khalaj Monfared, Hamed Okhravi, Shahin Tajik
ePrint Report ePrint Report
Voltage glitching is one of the most prominent fault injection techniques due to its effectiveness and simplicity. Although it is generally regarded as a spatially global fault method, in which the injected glitch uniformly affects all circuits on the die, several studies have observed that specific locations may be affected more than others. To characterize this phenomenon, we draw inspiration from methods used in electromagnetic interference (EMI) analysis. In this paper, we demonstrate that voltage attacks can be modeled as the transfer of conducted electromagnetic energy through the power delivery network (PDN) to the chip’s die. By analyzing voltage glitches in the frequency domain and modeling the PDN as a communication channel, we demonstrate that different frequency components of an injected glitch signal propagate through the network in distinct patterns. In this context, we further show that modulating the supply voltage with a single-frequency sinusoidal signal, rather than injecting a pulse-shaped glitch, enables an adversary to influence transistors in specific regions of the chip and thus induce localized faults. To validate these claims, we first propose a post-silicon profiling framework that identifies the frequency bands in which the system’s PDN is most vulnerable and maps the spatial regions of the chip affected by each frequency component. To this end, we perform extensive profiling on several FPGAs using distributed time-to-digital converters (TDCs) to measure the impact of injected signals across a range of frequencies. As a proof-of-concept, we also demonstrate successful localized voltage attacks on simple FSMs and AES-128 implementations with various placements, to further show the sensitivity of chip locations to injected energy at different frequencies. Our results reveal that even minor changes in design placement can significantly affect a circuit’s susceptibility to voltage-based fault attacks, either weakening or strengthening its resilience.
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Yanpei Guo, Hancheng Lou, Wenjie Qu, Zhuoyuan Xu, Jiaheng Zhang
ePrint Report ePrint Report
Polynomial commitment schemes (PCS) are a fundamental building block of modern proof systems. As proof system applications scale to increasingly large workloads, distributed PCS become essential for reducing prover time and memory pressure. Among existing PCS constructions, code-based PCS achieve significantly better concrete prover performance than group-based schemes by avoiding expensive elliptic-curve operations and operating over small-characteristic fields. However, despite these advantages, code-based PCS are notoriously difficult to distribute.

In this work, we present LigeSIS, the first distribution-friendly code-based multilinear PCS. LigeSIS achieves sublinear cross-node communication while keeping the final proof size independent of the number of machines. Our key insight is to replace Merkle-tree hashing with a homomorphic subset-sum hash over Goldilocks64, enabling algebraic aggregation of partial commitments produced by different nodes. To make this approach practical, we further introduce a preprocessing-accelerated subset-sum hash that reduces hashing overhead by up to $8\times$.

Our evaluation shows that, on a single node, LigeSIS achieves performance comparable to the state-of-the-art RS-based PCS WHIR (Eurocrypt’25). In distributed settings, LigeSIS exhibits near-linear scalability in prover time. Compared with distributed MKZG (S\&P’25), LigeSIS achieves a $24 \times$ improvement in prover time. Compared with PIP (Security’26), LigeSIS reduces cross-node communication by up to $20\times$.
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Min Yang, Jinxuan Du, Zihang Zhou, Dongcan Guo, Qingshu Meng
ePrint Report ePrint Report
The rapid proliferation of artificial intelligence (AI) applications—from large language models to deep neural networks—has led to an unprecedented demand for massive training data. This, in turn, has intensified privacy concerns, as sensitive information may be exposed during collaborative model training and inference. Privacy-preserving computing, particularly secure multi-party computation (MPC), offers a rigorous technical solution. Since Yao’s garbled circuits, nearly four decades of research have brought significant progress, yet MPC still faces fundamental challenges in efficiency and scalability. A handful of efficient and scalable MPC systems exist, but they almost invariably require heavy offline preprocessing—a burden that becomes prohibitive for modern Transformer‑based architectures with hundreds of billions of parameters. Conversely, the few approaches that eliminate preprocessing cover only a limited set of nonlinear functions, leaving a critical gap for real‑world machine learning.

In this paper, we propose MCU (Mask‑Compute‑Unmask), a novel MPC architecture that directly supports a broad spectrum of nonlinear functions without any offline preprocessing. MCU introduces a semi‑honest, non‑colluding helper party (HP) that acts as an active computational engine: parties additively mask their inputs, the HP computes the exact target function on the aggregated masked data, and the parties then unmask using locally known masks. This simple yet powerful paradigm enables a suite of constant‑round, scalable protocols, including general multiplication (2 rounds), power functions (2 rounds), exponentials and trigonometric functions (4 rounds), and sigmoid and softmax (6 rounds). All protocols achieve simulation‑based security and rely solely on additive masks and synchronized pseudorandom generators—no preprocessing, no polynomial approximations, and no accuracy loss. MCU effectively overcomes long‑standing efficiency and scalability barriers in privacy‑preserving machine learning, offering a practical solution for deploying large models such as Transformers in privacy‑sensitive environments.
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Yu Dai, Youssef El Housni, Dimitri Koshelev, Krijn Reijnders
ePrint Report ePrint Report
Subgroup membership testing (SMT) on an elliptic curve with non-trivial cofactor is essential to prevent small-subgroup attacks in cryptographic protocols. In the existing literature, there exist two non-trivial methods for SMT on elliptic curves with modest cofactor (typically a power of $2$): Pornin's approach tests membership by repeatedly dividing by prime divisors of the cofactor (mostly halving), finishing with Legendre symbols; Koshelev's approach replaces all divisions with Tate pairings (possibly in the quadratic extension of the base field), but requires non-degeneracy conditions that are not always met. In this paper, we observe that both approaches sit at the extremes of a single division-pairing trade-off. The resulting method, Divide-and-Pair, is always at least as fast as either Pornin's or Koshelev's method and strictly faster in many cases. We instantiate Divide-and-Pair on five curves in widespread use, including Curve25519, Curve448, GC256A, Four$\mathbb{Q}$ and JubJub. Our Go implementation, built on the open-source $\texttt{gnark-crypto}$ library, achieves significant speedups over state-of-the-art tests, namely of $2.4\times$ on Curve25519, of $1.6\times$ on Curve448, of $1.7\times$ on GC256A, of $8.2\times$ on Four$\mathbb{Q}$ and of $7.5\times$ on JubJub.
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Thanh-Phong Nguyen, Nguyen Tan Cam, Thanh-Hien Vu, Van-Than Huynh, Hieu-Minh Nguyen
ePrint Report ePrint Report
Neural differential cryptanalysis has recently been extended to related-key and multi-pair settings, enabling neural distinguishers to aggregate weak statistical biases across multiple ciphertext pairs. However, the statistical origin of the exploited signal remains insufficiently understood. In this work, we present a signal-centric analysis of related-key, multi-pair neural distinguishers across four block ciphers: PRESENT-80, SIMECK-32/64, LEA-128, and HIGHT.

We characterize ciphertext distributions using model-independent geometric metrics derived from Principal Component Analysis (PCA) embeddings and silhouette scores, and relate these data-level measurements to neural distinguishing performance under varying levels of aggregation. Across all evaluated ciphers, multi-pair aggregation amplifies weak ciphertext-level statistical biases through variance reduction, thereby extending distinguishability beyond the single-pair setting.

However, this effect is inherently limited by the progressive decay of ciphertext-level signal as the number of rounds increases, leading to well-defined difficulty boundaries where both geometric separability and neural performance collapse. In low-signal regimes, aggregation enables measurable, albeit limited, accuracy, indicating the presence of residual statistical structure. Generalization experiments further show that neural distinguishers fail to maintain predictive capability beyond the empirical boundary, with performance rapidly converging to the random baseline.

These findings suggest that neural distinguishing performance is fundamentally constrained by the underlying ciphertext-level signal rather than model capacity. Overall, this study provides a unified interpretation of the capabilities and limitations of multi-pair neural cryptanalysis.
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Harry Eldridge, Aditya Hegde, Brennon Brimhall, Gabrielle Beck, Matthew Green
ePrint Report ePrint Report
We propose a new private telemetry system for computing t-heavy hitters in the STAR (Davidson et al., CCS 2022) and POPSTAR (Li et al., USENIX 2024) model. In this setting, each client generates a report with the assistance of a lightweight Randomness Server and submits it to a central Aggregation Server, which can then locally compute only the heavy hitters. As compared to STAR and POPSTAR---which reveal either the full (pseudonymized) frequency histogram or a complex function of it---our protocol reduces leakage: the Aggregation Server learns non-heavy-hitter values only if their frequency exceeds a well-defined threshold. Additionally, while STAR and POPSTAR are insecure in the face of an Aggregation Server that colludes with clients, our protocol provides optimal security against such a colluding server. To achieve these privacy guarantees, our protocol efficiently adapts multi-dealer secret sharing (Eldridge et al., USENIX 2024) to the STAR/POPSTAR model and introduces a novel oblivious secret-share sampling protocol to ensure security against a colluding Aggregation Server. We implement and benchmark the performance of our protocol and find that it is practical for a number of use cases. Moreover, we show that it supports a tunable three-way tradeoff between correctness, efficiency and privacy.
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Paul Rösler, Katharina Schambach, Julian Thomas
ePrint Report ePrint Report
Atomic swaps allow two parties to exchange coins across blockchains without trust. Most existing solutions support a 1-to-1 transaction; however, the value ratio of two cryptocurrencies is usually not 1-to-1. In addition, these solutions often rely on blockchains with explicit support structures for atomic swaps, typically hashed timelocks (HTLCs) or smart-contract scripting. Thyagarajan et al. (SP'22) provide a solution for n-to-m swaps utilizing adaptor signatures instead, which offer better privacy for the participants. Significantly, all these approaches need timed transactions or a similar substitute on both sides, but not every blockchain supports timed transactions. Hoenisch et al. (ESORICS'22) demonstrate a concrete swap procedure between Bitcoin and Monero, where only one side needs timed transactions. We build upon both of these ideas to provide a generic solution for any blockchain, where only one side needs timed transactions.

We introduce a generic adaptor-signature protocol for n-to-m swaps. In doing so, we minimize assumptions compared to current solutions. Both sides lock their coins in shared (two-party signature) addresses, where they can only access the coins together. To prevent deadlocks, both parties are able to refund their coins from these addresses with pre-signed transactions. Our solution works with all relevant blockchains because it needs only standard signatures and a joint public key. Further, only one side needs timed transactions, and if each party acts in its best interest, there are two possible outcomes: If progress stalls, the side with timelocks refunds after a certain time, and the other side refunds immediately. Otherwise, one party redeems the other party's coins with pre-signed transactions, and the other party completes the swap after a timeout to prevent race conditions. We prove security in the universal composability framework and show privacy preservation via unlinkability and fungibility.
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Xavier Bultel, Khouredia Cisse
ePrint Report ePrint Report
Several modern applications, such as Signal or WireGuard, use efficient Noise-like implicit authentication key exchanges that require only a small number of exponentiations and two interactions. These protocols have been proven to be secure under the 'strong Diffie–Hellman' (SDH) assumption in the random oracle model (ROM). At ESORICS 2021, Ramacher, Slamanig and Weninger presented an extension to the implicit authenticated key exchange security model, which enables strong privacy properties to be captured in addition to key-secrecy, including man-in-the-middle privacy (ensuring privacy even if a session is interrupted) and forward privacy. They also proposed a protocol to instantiate their model. In this paper, we present an efficient Noise-like protocol that achieve privacy in this model. Our protocol is as efficient as Noise-like protocols that do not guarantee privacy in terms of exponentiations. Moreover, our protocol requires three interactions, which is optimal for this privacy model. It is also more efficient than the ESORICS 2021 protocol in terms of both exponentiations and interactions. Finally, we propose another round-optimal protocol, slightly less efficient in terms of exponentiations, but secure under the CDH assumption in the ROM.
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Mahdieh Heidaripour, Maryam Rezapour, Benjamin Fuller, Hoda Maleki, Gagan Agrawal
ePrint Report ePrint Report
Searchable encryption enables efficient querying over outsourced data while limiting server-side leakage. Existing methods for associative aggregation queries on multidimensional array data suffer from significant limitations:

* Use range structures that precompute ranges yielding either:

** Storage size proportional to the total domain size (Demertzis et al., TODS 2018/Falzon et al., PVLDB2022). ** Or linear-time search in the worst case (Chang et al., IEEE TKDE 2021).

* Bucket-based methods (Espiritu, Markatou, Tamassia, PoPETS 2022) are only practical when the largest bucket is small. Fully homomorphic encryption (FHE) approaches (Kushnir, Moskowich, Shaul, PoPETS 2024) remain computationally impractical.

Due to strong attacks on range schemes with access pattern leakage (Falzon et al., CCS 2020), we consider the task of oblivious search. We propose oblivious segment trees, which offer efficient storage and search. Our approach achieves polylogarithmic query complexity. Storage depends on the number of distinct values per dimension, not on the domain size. Under typical data distributions, segment trees are provably shorter than standard alternatives.

We evaluate performance on datasets with 1–3 dimensions and up to $5$ million entries. Across multidimensional datasets, our method reduces the number of stored items by $10$ to $10^{10}$ compared to prior non-FHE approaches. On a 32-thread machine, server-side query processing remains under $1.2$ seconds.
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Cody Freitag, Ilan Komargodski, Manu Kondapaneni, Jad Silbak
ePrint Report ePrint Report
Non-malleable codes allow a sender to transmit a message to a receiver, while providing a ``best-possible'' integrity guarantee to ensure that no attacker---who cannot already decode the message---can meaningfully tamper the message in transit. If tampered, the received message should either be invalid or unrelated to the original message. Non-malleable time-lock puzzles (TLPs) are a special case of non-malleable codes for bounded polynomial-depth tampering with very efficient encoding.

In this work, we give generic techniques for constructing non-malleable codes and non-malleable TLPs with improved rate, which captures the ratio of a message's length to its encoding length.

A key contribution of our work is identifying a security notion for non-malleability, which we term ``CCA-hiding'', sufficient for our compilers. CCA-hiding is a relaxation of CCA-security for encryption or commitments to the fine-grained setting of codes, and requires that the encoded message remains hidden, even given a decoding oracle for any other codeword. Intriguingly, CCA-hiding does not imply non-malleability in the fine-grained setting, as is the case for encryption and commitments.

Using our new techniques, we give the following constructions: -- Rate-1 CCA-hiding TLPs in the plain model. -- Rate-1 non-malleable codes for bounded polynomial-depth tampering in the auxiliary-input random oracle model (AI-ROM). -- Rate-(1/2) non-malleable TLPs in the AI-ROM.
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Bibhas Chandra Das, Nilanjan Datta, Avijit Dutta, Avishek Majumder, Debdeep Mukhopadhyay, Sikhar Patranabis, Subhabrata Samajder, Laltu Sardar
ePrint Report ePrint Report
Designing dynamic searchable symmetric encryption (DSSE) supporting conjunctive keyword queries over encrypted document collections is an important research area. Unfortunately, state-of-the-art conjunctive DSSE schemes such as ODXT (Patranabis et al., NDSS '21), and SDSSE-CQ and its variants (Zuo et al., PoPETS '25) either fail to achieve the desired levels of security (in particular, forward and/or backward privacy), or incur prohibitively large communication requirements and client-side computational overheads, which is undesirable for practical applications. In addition, all known conjunctive DSSE schemes that are both forward and backward private are quantum-broken due to their inherent reliance on discrete log-hard, prime-order cyclic groups.

In this paper, we address the open question of designing practically efficient, low-leakage, forward and backward private conjunctive DSSE with small communication requirements and small client-side overheads. Towards this goal, we introduce the first systematic and rigorously formal notions of backward privacy for conjunctive queries that naturally extend the corresponding notions of backward privacy for single-keyword DSSE. Next, as our main contribution, we propose a new framework for conjunctive DSSE called fp-GA-ODXT that improves upon both ODXT and SDSSE-CQ-variants by achieving full-fledged forward privacy and strong backward privacy guarantees, while incurring small client-side computation and low communication overheads. We then demonstrate two instantiations of our fp-GA-ODXT framework: 1) A concretely efficient, classically secure instance based on discrete log-hard groups and an RSA-based trapdoor permutation, which we implement and benchmark. Our experiments demonstrate that we achieve smaller communication overheads and client-side computation for both updates and conjunctive searches as compared to both ODXT and SDSSE-CQ-variants. These come at the cost of a mild increase in server computation (which we view as an acceptable tradeoff in practice). 2) A post-quantum instantiation based on lattices and isogenies of supersingular elliptic curves, thus solving the longstanding open question of designing asymptotically efficient, forward and backward private conjunctive DSSE schemes with post-quantum security.
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19 April 2026

Jens Groth
ePrint Report ePrint Report
We construct non-interactive zero-knowledge arguments for circuit satisfiability with perfect completeness, perfect zero knowledge and computational soundness. The non-interactive zero-knowledge arguments have sublinear size and very efficient public verification. Their size can even be reduced to a constant number of group elements if we allow the common reference string to be large. Our constructions rely on groups with pairings, and security is based on two new cryptographic assumptions; we do not use the Fiat-Shamir heuristic or random oracles.
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Damiano Abram, Giulio Malavolta, Lawrence Roy
ePrint Report ePrint Report
We propose a new method to construct homomorphic authentication codes supporting the evaluation of *non-deterministic* computations, extending the celebrated homomorphic lattice encodings [Boneh et al., Eurocrypt 2014]. Our approach relies on the hardness of the decomposed learning with errors problem (LWE), a recently introduced modification of Regev's LWE assumption.

We then use this new technical tool to make progress on several open problems in the literature. Specifically, we obtain: 1) A constrained pseudorandom function (PRF), where the evaluation of the PRF on the master key does not depend on the complexity of the constraint, except for its circuit depth. 2) A way to securely compress and re-expand LWE samples in the plain model. 3) An adaptively secure broadcast encryption scheme, with ciphertext and secret keys growing poly-logarithmically with the size of the encrypted set. 4) A pseudorandom obfuscation for all puncturable PRFs, additionally assuming the existence of sub-exponentially secure indistinguishability obfuscation (iO).

None of the above mentioned primitives was known to exist from lattice assumptions. As a bonus result, we also obtain a conceptually simple and direct heuristic construction of iO based on lattice techniques, which is not based on the function encryption-to-iO paradigm. We provide evidence that this approach can be used to build provably secure obfuscation for simple functionalities such as sampling lattice preimages using a hidden trapdoor.
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Shaolong TANG, Peng Jiang, Fuchun Guo, Willy Susilo, Liehuang Zhu
ePrint Report ePrint Report
Threshold blind signatures (TBS) allow any set of issuers whose size exceeds a predefined threshold to jointly generate a signature without learning the message. Adaptively secure TBS schemes allow the adversary to corrupt issuers at any point during protocol execution, capturing realistic threat models. Adaptive security methods rely on the algebraic group model (AGM) in security proofs to extract the discrete logarithm of the blinded protocol message. However, as a strong idealized assumption, AGM requires the adversary, upon outputting any group element, to also provide an explicit linear representation in terms of previously seen group elements. Constructing an adaptively secure TBS scheme without AGM remains challenging.

In this paper, we propose $\mathsf{Rainblind}$, the first TBS scheme achieving adaptive security without AGM. The core idea is to apply OR compilation between a discrete logarithm equality (DLEQ) statement and a decisional Diffie-Hellman (DDH) tuple statement such that the security proof does not need the AGM to extract the discrete logarithm of the blinded protocol message and instead only needs to extract the group element. Concretely, the DLEQ statement concerns the secret key, while the DDH-tuple statement is derived from a hash function. In real execution, it fails to satisfy the DDH-tuple statement by the uniform hash randomness, forcing the DLEQ branch. In security proof, by programming OR compilation into the DDH-tuple branch, we can leverage random elements to replace the DLEQ elements during the signing queries. To extract the group element, we design a non-interactive proof system $\mathsf{NIPS_{ped}}$. $\mathsf{Rainblind}$ is built from the tagged linear function ($\mathsf{TLF}$), so that the proof can answer adaptive corruption queries via the inversion oracle in the $t$-algebraic translation resistance assumption of $\mathsf{TLF}$, which implies DDH assumption. We also provide a plain signature $\mathsf{Sig_m}$ and a blind signature $\mathsf{BS_m}$ for transitioning to $\mathsf{Rainblind}$.
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Ming-Shing Chen, Tun-You Chien, Chun-Ming Chiu, Han-Hsuan Lin, Chun-Tao Peng, Bo-Yin Yang
ePrint Report ePrint Report
This paper presents an optimized implementation of the Hamming Quasi-Cyclic (HQC) key encapsulation mechanism, leveraging the additive fast Fourier transform (FFT) for polynomial multiplication. A primary challenge in applying FFT-based multiplication to HQC is that the polynomial degrees slightly exceed powers of two, making standard FFT approaches inefficient. To address this, we propose a new method combining the Frobenius additive FFT (FAFFT) with the Chinese Remainder Theorem (CRT) to efficiently multiply polynomials of these specific degrees. Such a combination is made possible by our new interpretation of FAFFT's Encode step as ring isomorphisms, from which we derive an exact formula for the modulus of any FAFFT-based polynomial multiplier.

In addition to the multiplication algorithm, we replace the Berlekamp-Massey decoder with an Extended Euclidean Algorithm (EEA) based method. The regular data flow of EEA facilitates the use of our highly optimized GF(256) SIMD arithmetic, leading to a faster execution speed.

Benchmarks demonstrate that our FFT-based approach significantly outperforms traditional Toom-Karatsuba methods, even at lower degrees, on the Arm Cortex-M4 platform. Our integrated optimizations result in a 19.5% and 20.4% speedups for the encapsulation and the decapsulation processes compared to the current state-of-the-art HQC-1 implementation.
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Antonio Giulio D'Antona, Charlotte Hoffmann, Krzysztof Pietrzak
ePrint Report ePrint Report
A proof of knowledge certifies that the prover “knows” a secret. This property is established by the existence of an extractor that, given access to the prover, can extract the secret. Unfortunately, this does not imply that a single entity has access to the secret in the clear, as it may be secret-shared among several parties and the proof computed using multiparty computation (MPC), or the secret may be embedded in a trusted execution environment (TEE) that only allows limited access to it.

Often, the ability to encumber a secret in this way breaks the security of a system; vote selling in e-voting schemes is one example. To address this, two recent papers introduced the notions of “Proofs of Complete Knowledge” (PoCK) [Kelkar et al., CCS’24] and “Individual Cryptography” [Dziembowski et al., CRYPTO’23]. While the goals and constructions in those works differ, both rely on the same key idea to prevent encumbrance. To compute a proof, the prover must evaluate a hash function on a huge number of inputs. One then assumes that only a fraction of those can be encumbered, while for the rest the prover must know the inputs in the clear, and these clear inputs are sufficient to extract the secret. Computing a huge number of hashes is a challenge even for an honest prover (who has the secret in the clear), so those works suggest using outdated Bitcoin mining hardware to make the scheme practical.

By forcing the prover to evaluate the hashes in a sequential manner, we could get meaningful security against encumbrance with far fewer hashes, especially against MPC, where round complexity is a major bottleneck.

As a concrete instantiation of this idea, we define and construct Sequential Proofs of Complete Knowledge (SPoCK). Our construction uses the PoCK of Kelkar et al. (which are based on Fischlin’s straight-line extractable proofs of knowledge). The computation of this PoCK is then embedded into the computation of the Proof of Sequential Work from [Cohen&Pietrzak, EUROCRYPT’18]. SPoCK thus have the potential to enable complete-knowledge or individual-cryptography primitives where honest parties can use standard hardware. We also propose a variant of this scheme that requires a large amount of memory throughout the evaluation, providing better security also against TEEs.
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Charlotte Hoffmann, Krzysztof Pietrzak
ePrint Report ePrint Report
A verifiable delay function (VDF), introduced by Boneh et al. [CRYPTO’18], on input $(x,T)$ produces an output $(y,\pi)$ where computing $y$ requires $T$ inherently sequential steps, and $\pi$ is a proof certifying correctness. VDFs have found numerous applications, and many of these rely on the assumption that honest parties can evaluate the VDF nearly as fast as adversaries.

To support this assumption, significant effort has been invested in developing dedicated VDF hardware (ASICs). However, such devices are expensive and produced in limited quantities, leaving only a small number of parties with access to fast VDF evaluation. A natural workaround is to offer “VDFs as a service,” where a server equipped with specialized hardware evaluates instances on behalf of clients. This approach, however, is unsuitable when the VDF input must remain private.

In this work, we introduce and construct blind VDFs, enabling secure VDF outsourcing without revealing the input. Inspired by blind signatures, our protocol allows a client to transform an input $x$ into a blinded instance $\alpha$, which is evaluated by the server. The server returns a result $\beta$, from this and its local state, the client can unblind to recover the correct output $(y,\pi)$, while the server learns nothing about $x$.

We realize this notion by constructing a blinded version of Pietrzak’s VDF [ITCS’19]. In the original scheme, computing $y$ requires $T$ sequential steps, while generating the proof $\pi$ can be done in $O(T/S)$ parallel time using $O(S)$ space (e.g., $O(\sqrt{T})$ time and space). In our blind variant, the server performs the $T$ sequential steps and sends $O(S)$ data to the client, who completes the unblinding in $O(T/S)$ time. By allowing slightly more interaction, we obtain a protocol where the client’s work is small, while the server performs essentially the same computation as in the unblinded VDF.
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Sanajit Patra, Ratna Dutta, Jayashree Dey
ePrint Report ePrint Report
In this work, we propose the first code-based $\mathsf{uPKE}$ from the hamming quasi-cyclic public key encryption scheme $(\mathsf{hqcPKE})$ of Gaborit et al. by integrating an efficient key-update mechanism utilizing a carefully designed deterministic sampling algorithm. Our sampling algorithm exploits a structured permutation set preserving Hamming weight and satisfying specific algebraic properties that is of independent interest. More positively, our protocol allows unbounded key updates free from the cumulative error issues inheriant to lattice based designs and supports asynchronous key updates, authorizing senders to update the public key independently. We formally establish the security of the proposed construction against indistinguishability under chosen-randomness and chosen-plaintext attack $(\mathsf{IND}\text{-}\mathsf{CR}\text{-}\mathsf{CPA})$ in standard model considering decisional quasi-cyclic syndrome decoding with parity $(\mathsf{DQCSDP})$ assumption. We emphasize that in comparison with existing post-quantum secure asynchronous schemes supporting unbounded updates, our construction achieves in the standard model instead of random oracle model significantly improved storage and communication efficiency, particularly in terms of public key size, ciphertext size and update ciphertext size. From a computational perspective, our design enables a more efficient public key update procedure and exhibits comparable performance for key generation, encryption, decryption and secret key update.
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Emanuele Bellini, Mohamed Rachidi, Sharwan K. Tiwari
ePrint Report ePrint Report
We present CLAASP-MP, a monomial prediction (MP) tool based on the three-subset division property without unknown subset (3SDP-woU), integrated into CLAASP, a library for automated analysis of symmetric key cryptographic primitives. The propagation rules of 3SDP-woU are encoded as a Mixed Integer Linear Programming (MILP) model generated directly from the CLAASP component graph, covering the main building blocks used in modern symmetric designs, including S-boxes, linear layers, Boolean word operations, modular addition and multiplication, and linear and nonlinear feedback shift register updates.

Using this model for selected output bits, CLAASP-MP computes algebraic normal form (ANF) (for a small number of rounds), derives superpolies for a chosen cube, and computes a tight upper bound on the algebraic degree with respect to plaintext, key, or IV variables. A monomial is absent if its ANF coefficient is zero, if it does not appear in the superpoly, or if the algebraic degree is too small for it to occur; in all such cases, the output is balanced and yields an integral distinguisher.

We evaluate \name{} on block ciphers, permutations, and stream ciphers implemented in \claasp{}. We introduce an exact bit-level MILP modeling technique for modular multiplication and apply it to provide the first independent algebraic analysis of the MSX block cipher, identifying integral properties that persist up to 7 rounds for MSX-128. Furthermore, we reproduce known distinguishers and identify new cubes for several block ciphers and extend the best-known integral distinguishers of ChaCha and Salsa permutations from 6 and 5 rounds, respectively, to 6.75 rounds. We also discovered new integral distinguishers for Bivium using several 36-dimensional cubes and extended the exact computation of the algebraic degree of Trivium to later initialization clocks while reproducing many published superpolies.

These results show that CLAASP-MP provides a unified and practical MILP-based framework for monomial prediction and algebraic analysis across a wide range of symmetric primitives.
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Kwangjo Kim
ePrint Report ePrint Report
We investigate the security of AES-128/192/256 when implemented as ReLU-based neural networks via the natural sum-of-corners construction. Although these implementations are bit-exact on Boolean inputs, they extend AES into a continuous piecewise-linear function over $\mathbb{R}^{128}$. We show that under real-valued oracle access, such neural realizations admit deterministic linear-time master-key recovery. The attack exploits a geometric property of the natural XOR (AddRoundKey) layer: for corner parameter c < 1, ReLU activations partition the input space into key-dependent linear regions. Using symmetric perturbations, exactly one key hypothesis preserves linear-region membership, enabling bitwise recovery through simple output-equality tests. We formalize this phenomenon via a local separability lemma and obtain attack complexity O(128R) neural queries for R rounds. Experiments over 1,000 independent random keys for AES-128, AES-192, and AES-256 achieve 100% recovery success. The vulnerability is independent of key size and round count; it stems solely from exposing a key-dependent XOR layer inside a continuous neural architecture. Our results reveal a fundamental gap between Boolean security and geometric security in neural implementations of cryptographic primitives.
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