What a lovely hat

Group signatures enable users to sign on behalf of a group while preserving anonymity, with accountability provided by a designated opener. The first rigorous model for dynamic groups (Bellare, Shi, Zhang, CT--RSA '05) captured anonymity, non-frameability, and traceability, later extended with trace-soundness (Sakai et al., PKC '12) and non-claimability (introduced as ``opening-soundness'' by Bootle et al., ACNS '16 & JoC '20). In practice, issuer and opener are often distinct entities,...

Emails are one of the main forms of digital communication. They were designed to provide many guarantees that have surprisingly not yet been formalized in cryptography. Yet many of the guarantees emails were designed to provide have not been formalized in cryptography. This paper models an important feature of email applications: the plausible deniability of including Bcc recipients. Concretely, - we define a basic (theoretical) email application capturing these guarantees in Constructive...

The analysis of quantum algorithms which query random, invertible permutations has been a long-standing challenge in cryptography. Many techniques which apply to random oracles fail, or are not known to generalize to this setting. As a result, foundational cryptographic constructions involving permutations often lack quantum security proofs. With the aim of closing this gap, we develop and prove soundness of a compressed permutation oracle. Our construction shares many of the attractive...

Whilst many key exchange and digital signature systems still rely on NIST P-256 (secp256r1) and secp256k1, offering around 128-bit security, there is an increasing demand for transparent and reproducible curves at the 256-bit security level. Standard higher-security options include NIST P-521, Curve448, and Brainpool-P512. This paper presents ECCFROG522PP ('Presunto Powered'), a 522-bit prime-field elliptic curve that delivers security in the same classical $\sim$260-bit ballpark as NIST...

Oblivious Linear Evaluation (OLE) is an algebraic generalization of oblivious transfer (OT) that forms a critical part of a growing number of applications. An OLE protocol over a modulus $q$ enables the receiver party to securely evaluate a line $a\cdot X+b$ chosen by the sender party on a secret point $x\in\mathbb{Z}_q$. Motivated by the big efficiency gap between OLE and OT and by fast OT extension techniques, we revisit the question of reducing OLE to OT, aiming to improve the...

The long-term success of cryptocurrencies largely depends on the incentive compatibility provided to the validators. Bribery attacks, facilitated trustlessly via smart contracts, threaten this foundation. This work introduces, implements, and evaluates three novel and efficient bribery contracts targeting Ethereum validators. The first bribery contract enables a briber to fork the blockchain by buying votes on their proposed blocks. The second contract incentivizes validators to voluntarily...

A weak pseudorandom function $F: \mathcal{K} \times \mathcal{X} \rightarrow \mathcal{Y}$ is said to be ring key-homomorphic if, given $F \left(k_{1}, x \right)$ and $F \left(k_{2}, x \right)$, there are efficient algorithms to compute $F \left(k_{1} \oplus k_{2}, x \right)$ and $F \left(k_{1} \otimes k_{2}, x \right)$ where $\oplus$ and $\otimes$ are the addition and multiplication operations in the ring $\mathcal{K}$, respectively. A recent work by Alamati et al. (CT-RSA' 23) initiated the...

Shannon’s 1949 theorem defines perfect secrecy as a condition where every possible message remains equally likely given any ciphertext, which requires a key at least as long as the message. This definition, while foundational, is binary and assumes uniform message priors—assumptions rarely met in real communication systems. It cannot express the fact that secrecy degrades gradually as key entropy decreases, and it does not account for semantic structure or contextual knowledge available to...

This manuscript introduces Semantic Holder (SH), the opposability primitive within the Chaotic Affine Secure Hash (CASH) toolkit, completing the framework’s implementation of the Q2CSI philosophy. SH enables legally opposable interpretations through algebraic extraction from polynomial iteration traces, working in concert with CEE (confidentiality) and AOW (reliability). Building upon the Affine Iterated Inversion Problem (AIIP) foundation, SH provides mathematically verifiable legal...

In 1997, Kani proved Kani's lemma, which asserts that a commutative diagram of four $g$‑dimensional abelian varieties induces an isogeny between product abelian varieties of dimension $2g$, in counting the number of genus-$2$ curves admitting two distinct elliptic subcovers. In these years, Kani’s lemma plays a fundamental role in isogeny-based cryptography: Kani’s lemma has found numerous cryptographic applications, including both cryptanalysis and protocol construction. However, direct...

We present a formally-verified (in Lean 4) framework for translating symbolic cryptographic proofs into the computationally-sound ones. Symbolic cryptography is a well-established field that allows reasoning about cryptographic protocols in an abstract way and is relatively easy to verify using proof assistants. Unfortunately,  it often lacks a connection to the computational aspects of real-world cryptography. Computationally-sound cryptography, on the other hand, captures this connection...

Garbled Circuits (GC) are a foundational primitive for secure two-party computation (2PC). Garbled Private Information Retrieval (GPIR) is a GC technique for looking up a public array or database (DB) on a private index unknown to either party. GPIR immediately enables GC evaluation of functions implemented as a publicly known lookup table (LUT). However, GPIR is costly. It can be realized by a linear scan, by adapting Garbled RAM, by stacking GC branches implementing access to table...

Data availability sampling (DAS) enables clients to verify availability of data without downloading it entirely. This concept is crucial to Ethereum's roadmap. An instantiation of this concept, known as PeerDAS, relies at its core on a variant of KZG polynomial commitments and is set to be integrated into Ethereum. To assess the security of PeerDAS, Wagner and Zapico (ePrint 2024) provided a formal analysis, proving its security as a cryptographic primitive. However, their proof relies on...

We introduce modular forms and Hecke operators to cryptography and propose the Hecke problem as a new foundation for post-quantum cryptography. Given two modular forms, the Hecke problem asks to recover the Hecke operator that maps one to the other. While there is a deep relation to isogeny problems through the modularity theorem, this problem is rooted in arithmetic geometry and differs fundamentally in structure and mechanism. We prove NP-hardness of this problem and use it to construct a...

Privacy-preserving machine learning (PPML) has become increasingly important due to the need to protect sensitive data during training and inference. Secure multiparty computation (MPC) and homomorphic encryption (HE) have emerged as foundational technologies, enabling secure computation over private data. In this work, we provide a systematic comparative overview of MPC frameworks for PPML, focusing on protocols that introduce novel approaches rather than incremental improvements....

Incrementally verifiable computation (IVC) is a powerful cryptographic primitive, particularly suited for proving long-running machine computations. Previous work shows that IVC can be constructed by recursively composing SNARKs. Unfortunately, theoretical challenges limit the provable security of known IVC constructions. Recursive composition may quickly lead to a blowup in extraction time and may require arithmetic circuits to enforce constraints about random oracle calls. Furthermore,...

Distributed systems require robust, transparent mechanisms for verifiable temporal ordering to operate without trusted authorities or synchronized clocks. This paper introduces Affine One-Wayness (AOW), a new cryptographic primitive for post-quantum temporal verification based on iterative polynomial evaluation over finite fields. AOW provides strong temporal binding guarantees by reducing its security with a tight reduction to the hardness of the dis crete logarithm problem in...

Bilinear pairings have emerged as a fundamental tool in public-key cryptography, enabling advanced protocols such as Identity-Based Encryption (IBE), short signatures, and zero-knowledge proofs. This paper focuses on optimizing pairing computations on curves with embedding degree 2, addressing both theoretical foundations and practical implementations. We propose an optimized double-and-add ladder algorithm that leverages the technique of y-coordinate recovery, achieving superior...

Password-Hardened Encryption (PHE) protects against offline brute-force attacks by involving an external ratelimiter that enforces rate-limited decryption without learning passwords or keys. Threshold Password-Hardened Encryption (TPHE), introduced by Brost et al. (CCS’20), distributes this trust among multiple ratelimiters. Despite its promise, the security foundations of TPHE remain unclear. We make three contributions: (1) We uncover a flaw in the proof of Brost et al.’s TPHE scheme,...

Verifiable Secret Sharing (VSS) is a fundamental primitive in threshold cryptography and multi-party computation. It preserves secrecy, integrity, and availability of a shared secret for a fixed set of parties, with a subset of them being malicious. In practical applications, especially when the secret sharing is expected to be maintained over long durations, the VSS scheme should be able to cater to a dynamic setting where involved parties may change. The primitive known as Dynamic...

Multi-party computation (MPC) enables a set of mutually $n$ distrusting parties to compute any function on their private inputs. Mainly, MPC facilitates agreement on the function’s output while preserving the secrecy of honest inputs, even against a subset of $t$ parties controlled by an adversary. With applications spanning from anonymous broadcast to private auctions, MPC is considered a cornerstone of distributed cryptography, and significant research efforts have been aimed at making MPC...

We make progress on the foundational problem of determining the strongest security notion achievable by homomorphic encryption. Our results are negative. We prove that a wide class of semi-homomorphic public key encryption schemes (SHPKE) cannot be proven IND-PCA secure (indistinguishability against plaintext checkability attacks), a relaxation of IND-CCA security. This class includes widely used and versatile schemes like ElGamal PKE, Paillier PKE, and the linear encryption system by Boneh,...

Weintroduce the Chaotic Entropic Expansion (CEE), a new one-way function based on iterated polynomial maps over finite fields. For polynomials f in a carefully defined class Fd, we prove that N iterations preserve min-entropy of at least log2q − N log2d bits and achieve statistical distance ≤ (q − 1)(dN − 1)/(2√q) from uniform. We formalize security through the Affine Iterated Inversion Problem (AIIP) and provide reductions to the hardness of solving multivariate quadratic...

We introduce the Affine Iterated Inversion Problem (AIIP), a new candidate hard problem for post-quantum cryptography, based on inverting iterated polynomial maps over finite fields. Given a polynomial f ∈ Fq[x] of degree d ≥ 2, an iteration parameter n, and a target y ∈ Fq, AIIP requires finding an input x such that f(n)(x) = y, where f(n) denotes the n-fold composi tion of f. We establish the computational hardness of AIIP through two independent analytical frameworks: first, by...

HotStuff has gained widespread application in scenarios such as consortium chains in recent years due to its linear view change and pipelined decision making mechanisms. Although there have been studies on the performance of this algorithm, there remains a lack of analysis and formal termination proofs regarding its composability. This paper, for the first time, constructs a comprehensive formal system for the HotStuff protocol in a partially synchronous network environment under the...

The advancement of quantum computing threatens traditional public-key cryptographic algorithms such as RSA and ECC, both vulnerable to Shor’s algorithm. As most Transport Layer Security (TLS) deployments still rely on these quantum-vulnerable algorithms for key exchange and digital signatures, the transition to Post-Quantum Cryptography (PQC), standardized by NIST, has become increasingly urgent. Given the critical role of TLS in securing Internet communications, identifying and...

Privacy-preserving machine learning (PPML) is a powerful tool for multiple parties to collaboratively train a model or perform model inference without exposing their private data in the context of Internet of things. A key challenge in PPML is the efficient evaluation of non-polynomial functions. In this work, we propose NASE, a neat and accurate secure exponentiation protocol for radius basis function (RBF) kernel evaluation. Leveraging the property of the RBF kernel, NASE enjoys a...

Sigma protocols are fundamental cryptographic tools, serving as the foundation of many practical schemes—most notably, the Schnorr identification and signature schemes. To prove the security of Sigma protocols, one typically reduces breaking a Sigma protocol to solving a presumed hard problem (e.g., computing the discrete logarithm in a certain group). In many settings, however, these reductions are not tight: given an adversary that breaks a Sigma protocol with probability $\varepsilon$,...

Layer-2 protocols are pivotal in enhancing the scalability of blockchain systems, enabling faster off-chain transactions while maintaining security. These protocols can bridge consensus-based blockchain systems and advanced applications, such as Multiparty Computation (MPC) protocols, often defined within the Universal Composability (UC) Framework. However, despite the existence of some UC-defined protocols, there is currently no comprehensive UC definition for isomorphic multiparty state...

In this paper, we specifically review Xu et al.’s quantum blind signature scheme for distributed e-voting systems, which primarily focuses on simulating real-life e-voting. The scheme aims to ensure voter anonymity in an e-voting system. However, we found that it not only suffers from identity impersonation attacks but also lacks the blindness property essential to a blind quantum signature. To address these shortcomings, we propose a new quantum blind signature scheme that leverages quantum...

SNARKs enable compact proofs that an NP statement is true and that the prover knows a valid witness. They have become a key building block in modern smart contract applications, including rollups and privacy-focused cryptocurrencies. In the widely used Groth16 framework, however, long statements incur high costs. A common workaround is to pass the statement’s hash to the SNARK and move the statement into the witness. The smart contract then hashes the statement first, and the circuit that...

Symmetric cryptography is confronting threats posed by quantum computing, including Grover's search algorithm and Simon's algorithm. In the fault-tolerant quantum computation, the limited qubit count, connectivity constraints, and error rates of quantum hardware impose stringent requirements on the implementation of cryptographic quantum circuits. Constructing low-resource quantum circuit models forms the foundation for evaluating algorithmic resistance to quantum threats. In this work, we...

In this paper, we present an optimized construction of the Homomorphic Polynomial Public Key (HPPK) cryptosystem, a novel framework designed to provide enhanced security and efficiency in the post-quantum era. Our work introduces a layered cryptographic design that combines modular arithmetic permutations with an innovative additive random masking technique. This approach effectively obscures the underlying factorizable structure of the public key, thereby mitigating vulnerabilities to known...

Designing cryptographic protocols and proving these rigorously secure is an arduous and challenging task. Among the methods commonly used to prove security of cryptographic protocols, formalizing it in Canneti's Universal Composability (UC) Framework offers several benefits: (1) Modular design, (2) demonstrating that security remains under arbitrary composition and concurrent execution, (3) the security against any computationally polynomially bound adversary. However, working within the UC...

In this work we analyze a problem strictly linked with the Rational Reconstruction, which forms the foundation of some post-quantum Quasi-Cyclic Moderate-Density Parity-Check and Quasi-Cyclic Low-Density Parity-Check code-based schemes such as LEDAkem and BIKE. Given a polynomial in a cyclic ring as input, our aim is to recover two polynomials, with specific properties, whose ratio is the input one. The starting point of this work is the paper of Bardet, Dragoi, Luque, and Otmani, which...

This article presents the architectural design of Zero Knowledge Non-Repudiation (ZK-NR), a layered cryptographic protocol enabling post-quantum secure, legally interpretable, and verifiably non-repudiable attestations. Built upon STARK-based zero-knowledge proofs, hybrid post-quantum signatures, and entropy-accumulating ledger anchoring, ZK-NR satisfies the structural properties of both the Q2CSI framework and the NIZK-E model. The protocol achieves semantic interpretability by structurally...

Randomness is a fundamental requirement in cryptographic systems, enabling secure encryption, commitments, and zero-knowledge proofs. However, real-world randomness sources often suffer from weaknesses that adversaries can exploit, leading to significant security vulnerabilities. While deterministic randomness extraction from a single min-entropy source is impossible, two-source extractors provide a robust solution by generating nearly uniform randomness from two independent weak sources....

As quantum computing technology rapidly advances, threats to existing symmetric-key and public-key cryptosystems are becoming increasingly real. In this study, we implement a SHA-1 quantum circuit that operates efficiently in a quantum computing environment. We optimize the quantum circuit, focusing on minimizing total circuit depth, a key performance indicator of quantum algorithms. The SHA-1 quantum circuit implementation used 985 qubits, resulting in a measured circuit depth of 9,026....

Incrementally Verifiable Computation (IVC) allows one to prove the correctness of a computation of potentially unbounded length in an incremental way, while a computationally weak client can efficiently check its correctness in time sublinear in the computation's length. IVC is particularly useful in several real-world applications such as scalable blockchains, distributed computation, and verifiable machine learning. Yet, most existing IVC schemes are only provably secure for constant-depth...

Verifiable Databases (VDBs) let clients delegate storage to an untrusted provider while maintaining the ability to verify query results. Since databases are foundational and storage delegation is increasingly common, VDBs address a critical need. Existing VDB designs face several limitations: approaches based on general-purpose proof systems (e.g., SNARKs) offer high expressivity but at the cost of cumbersome intermediate representations, heuristic assumptions, and heavy cryptographic...

Message dissemination is a fundamental building block in distributed systems and guarantees that any message sent eventually reaches all parties. State of the art provably secure protocols for disseminating messages have a per-party communication complexity that is linear in the inverse of the fraction of parties that are guaranteed to be honest in the worst case. Unfortunately, this per-party communication complexity arises even in cases where the actual fraction of parties that behave...

Human verification under adversarial information flow operates as a cost-bounded decision procedure constrained by working memory limits and cognitive biases. We introduce the Verification Cost Asymmetry (VCA) coefficient, formalizing it as the ratio of expected verification work between populations under identical claim distributions. Drawing on probabilistically checkable proofs (PCP) and parameterized complexity theory, we construct dissemination protocols that reduce verification for...

Threshold encryption enables a sender to encrypt a message towards $n$ recipients, such that any sufficiently large subset can decrypt the message, whereas any subset of too small size cannot. Silent threshold encryption additionally requires that all recipients can generate their public keys independently of each other, without engaging in an interactive distributed key generation protocol. In this work, we present a simple blueprint for constructing such silent threshold encryption...

The Learning with Rounding (LWR) problem, introduced as a deterministic variant of Learning with Errors (LWE), has become a promising foundation for post-quantum cryptography. This Systematization of Knowledge (SoK) paper presents a comprehensive survey of the theoretical foundations, algorithmic developments, and practical implementations of LWR-based cryptographic schemes. We introduce LWR within the broader landscape of lattice-based cryptography and post-quantum security, highlighting...

The fundamental incompatibility between confidentiality, reliability, and le gal opposability, formalized as the CRO trilemma, imposes an entropic bound Γ_CRO on cryptographic security in contextual adversarial settings. This pa per introduces Q2CSI (Quantum Composable Contextual Security Infras tructure), a layered framework resolving this trilemma through dialectical separation. Q2CSI decomposes security guarantees into three isolated yet composable layers: Iron (reliability:...

Deep learning-based side-channel analysis (DLSCA) has demonstrated remarkable performance over the past few years. Even with limited preprocessing and feature engineering, DLSCA is capable of breaking protected targets, sometimes requiring only a single attack trace. In the DLSCA context, the commonly investigated countermeasures are Boolean masking and desynchronization. While the exact mechanisms of how DLSCA breaks masking are less understood, the core idea behind handling...

The syndrome decoding problem is one of the NP-complete problems lying at the foundation of code-based cryptography. The variant thereof where the distance between vectors is measured with respect to the Lee metric, rather than the more commonly used Hamming metric, has been analyzed recently in several works due to its potential relevance for building more efficient code-based cryptosystems. The purpose of this article is to present a zero-knowledge proof of knowledge for this variant of...

The impending threat posed by large-scale quantum computers necessitates a reevaluation of signature schemes deployed in blockchain protocols. In particular, blockchains relying on ECDSA, such as Bitcoin and Ethereum, exhibit inherent vulnerabilities due to on-chain public key exposure and the lack of post-quantum security guarantees. Although several post-quantum transition proposals have been introduced, including hybrid constructions and zero-knowledge-based key migration protocols, these...

Symmetric encryption allows us to establish a secure channel based on a shared, strong key. However, users cannot remember or cannot store such keys securely. Password-Authenticated Key Exchange (PAKE) protocols address this by using low-entropy, human-memorizable passwords to establish secure channels. PAKEs are widely used and are foundational in practical cryptographic protocols, but while cryptographic tools like Key Encapsulation Mechanism (KEM) and Signatures have been implemented to...

In this note, we present a new instantiation of the hash-based multi-signature framework introduced by Drake, Khovratovich, Kudinov, and Wagner (CiC Vol 2 Issue 1, eprint 2025/055) for Ethereum’s consensus layer. Inspired by a recent work of Khovratovich, Kudinov, and Wagner (Crypto 2025, eprint 2025/889), we instantiate the framework with a novel incomparable encoding that improves the tradeoff between signature size and verification hashing. The purpose of this document is to make explicit...

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 $N$. The breakthrough work of Lin-Mook-Wichs (STOC’23) presented the first DEPIR construction from the Ring-LWE assumption. This...

Fully Homomorphic Encryption (FHE) enables computation over encrypted data and is considered a fundamental tool for privacy-preserving systems. Despite significant theoretical progress, its practical adoption remains limited. One contributing factor is the absence of reusable, application-level components suitable for integration into real-world systems. This work introduces a library of FHE components developed through a competition- based framework. The components are outcomes of a...

Despite the growing popularity of blockchains, their scalability remains a significant challenge. Layer-2s (L2s) aim to address this by introducing an operator to process transactions off-chain and post compact summaries to the Layer-1 (L1). However, existing L2 designs struggle with unsatisfactory throughput improvements, complex exit games, limited data availability, stringent synchronization requirements or high computational overhead for users. This paper introduces PlasmaFold, a...

Non-degenerate bilinear maps on elliptic curves, commonly referred to as pairings, have many applications including short signature schemes, zero-knowledge proofs and remote attestation protocols. Computing a state-of-the-art pairing at the $128$-bit security level, such as the optimal ate pairing over the curve BLS12-381, is very costly due to the high complexity of some of its sub-operations: most notable are the Miller loop and final exponentiation. In the past ten years, a few optimized...

Matrix inversion is a fundamental operation, but performing it over encrypted matrices remains a significant challenge. This is mainly due to the fact that conventional inversion algorithms—such as Gaussian elimination—depend heavily on comparison and division operations, which are computationally expensive to perform under homomorphic encryption. To mitigate this, Ahn et al. (ESORICS 2023) introduced an inversion method based on iterative matrix multiplications. However, their approach...

While digital signatures serve to confirm message integrity and the identity of the signer, the inherent link between the public key and the signer’s identity can pose challenges in anonymized networks or applications focused on preserving privacy. Signatures with randomiz- able keys aim to disentangle the signer’s identity from their public key, thus preserving the signature’s validity. This approach ensures that the signature, even with a randomized key, maintains its verifiability...

Single decryptor encryption (SDE) is public key encryption (PKE) where the decryption key is an unclonable quantum state. Coladangelo, Liu, Liu, and Zhandry (CRYPTO 2021) realized the first SDE assuming subexponentially secure indistinguishability obfuscation (iO) and one-way functions (OWFs), along with the polynomial hardness of the learning with errors (LWE) assumption. Since then, SDE has played a pivotal role in recent advances in quantum cryptography. However, despite its central...

Quantum copy-protection is a foundational notion in quantum cryptography that leverages the governing principles of quantum mechanics to tackle the problem of software anti-piracy. Despite progress in recent years, precisely characterizing the class of functionalities that can be copy-protected is still not well understood. Two recent works, by [Coladangelo and Gunn, STOC 2024] and [Ananth and Behera, CRYPTO 2024, showed that puncturable functionalities can be copy-protected. Both works...

This paper builds the foundation for a cryptosystem based on p-adic representations of supersingular elliptic curve isogenies generated through Engel expansions of Laurent series. This mathematical framework manifests as a lightweight encryption scheme implemented on ESP32 microcontrollers for IoT applications. Efficient isogeny paths are constructed for quantum-resistant primitives secured against Shor's algorithm by decomposing elements into Engel sequences. Performance analysis confirms...

The approximate Closest Vector Problem (CVP) is a core computational problem underlying many post-quantum lattice-based signature schemes, including Dilithium, one-more-ISIS, and HuFu. While the security of these schemes is typically expressed in terms of the Inhomogeneous Short Integer Solution (ISIS) problem, it is well-known that ISIS can be efficiently reduced to approximate CVP. Despite its foundational role, approximate CVP with non-negligible approximation factors remains far less...

In 2023, Srinath Setty, Justin Thaler, and Riad Wahby published a paper that describes a novel lookup argument with efficient verification called Lasso. We present a focused and accessible overview of the Lasso lookup argument that stands for the foundational component of the Jolt ZK-VM. This article distills the core principles behind Lasso: the sum-check protocol, multilinear polynomials and their extensions, Spark commitment, offline memory-checking, and the evolution of Spark called...

Authenticated dictionaries (ADs) enable secure lookups to a dictionary hosted by an untrusted server and are a key component of various real-world applications, including transparency systems and cryptocurrencies. Despite significant overlap in techniques for building ADs and related primitives, such as memory checkers and accumulators (i.e., authenticated sets), these relationships have yet to be formalized. In this work, we give a rigorous treatment of ADs and prove their precise...

This paper introduces ZK-NR, a modular cryptographic protocol designed to ensure privacy-preserving non-repudiation in the co-production of digital public services. By integrating Merkle commitments, zero-knowledge proofs (STARKs), threshold BLS signatures, and post-quantum Dilithium authentication, ZK-NR enables the creation of secure, verifiable, and auditable evidence across decentralized infrastructures. Unlike traditional digital signatures or blockchain-based logs, ZK-NR provides...

A multi-designated verifier signature (MDVS) is a digital signature that empowers a signer to designate specific verifiers capable of verifying signatures. Notably, designated verifiers are allowed to not only verify signatures but also simulate “fake” signatures indistinguishable from real ones produced by the original signer. Since this property is useful for realizing off-the-record (i.e., deniable) communication in group settings, MDVS is attracting attention in secure messaging....

Cryptographic security protocols, such as TLS or WireGuard, form the foundation of a secure Internet; hence, a long line of research has shown how to formally verify their high-level designs. Unfortunately, these formal guarantees have not yet reached real-world implementations of these protocols, which still rely on testing and ad-hoc manual audits for security and correctness. This gap may be explained, in part, by the substantial performance and/or development overhead imposed by prior...

Quantum computing is often introduced through the lens of linear algebra with notation that is inherited from quantum mechanics. In this paper, we take an operational view of quantum computing that is easy to demonstrate programmatically. The hope is that this viewpoint will (1) demystify quantum computing and make it more accessible to a wider audience, particularly computer science students and software engineers, and (2) possibly serve as the basis of a formal foundation for automatically...

Onion routing is a popular practical approach to anonymous communication, and the subject of a growing body of foundational theoretical work aiming to design efficient schemes with provable anonymity, the strongest notion of which is full anonymity. Unfortunately, all previous schemes that achieve full anonymity assume the synchronous communication setting, which is unrealistic as real networks may experience message loss and timing attacks that render such schemes insecure. Recently,...

FROST and its variants are state-of-the-art protocols for threshold Schnorr signatures that are used in real-world applications. While static security of these protocols has been shown by several works, the security of these protocols under adaptive corruptions—where an adversary can choose which parties to corrupt at any time based on information it learns during protocol executions—has remained a notorious open problem that has received renewed attention due to recent standardization...

We introduce and analyze a novel class of binary operations on finite-dimensional vector spaces over a field K, defined by second-order multilinear expressions with linear shifts. These operations generate polynomials whose degree increases linearly with each iterated application, while the number of distinct monomials grows combinatorially. We demonstrate that, despite being non-associative and non-commutative in general, these operations exhibit power associativity and internal...

Distributed Randomness Beacons (DRBs) provide secure, unbiased random numbers for decentralized systems, yet face limitations. Many rely on quantum-vulnerable cryptographic assumptions, compromising security in asynchronous networks with unbounded delays. Traditional Verifiable Secret Sharing (VSS)-based DRBs, following a share-consensus-reconstruct paradigm, are often unsuitable for asynchronous settings due to circular dependencies between beacon generation and consensus. We propose...

As generative models continue to evolve, verifying the authenticity, provenance, and integrity of digital media has become increasingly critical—particularly for domains like journalism, digital art, and scientific documentation. In this work, we present a decentralized verifiable media ecosystem for managing, verifying, and transacting authentic digital media using zero-knowledge proofs (ZKPs). Building on VIMz (Dziembowski et al., PETS'25), we extend the framework in three key...

The leader election problem requires a set of $n$ parties, out of which up to $t$ can be Byzantine, to elect a leader uniformly at random such that no two parties disagree on the elected leader and an honest leader is elected with constant probability. The Scalable Leader Election protocol published in SODA'2006 is an important breakthrough in solving this problem efficiently for all but $o(1)$ of the parties. They achieve a protocol for $t < (\frac{1}{3} - \epsilon)n$ (for $\epsilon =...

Secret sharing (SS) is a foundational cryptographic primitive with diverse applications, including secure multiparty computation and conditional disclosure of secrets. While traditional schemes have primarily emphasized information-theoretic security, recent advancements have increasingly leveraged computational assumptions to achieve more efficient constructions and support broader access policies. Despite these successes, most existing computational secret sharing (CSS) schemes are limited...

This work addresses the problem of Byzantine Fault-Tolerant (BFT) Total-Order Broadcast (TOB) in a dynamically available setting, where parties can transition between online and offline states without knowing the number of active parties. Existing dynamically available protocols rely on a synchronous network assumption, which means their latency remains tied to the pessimistic network delay $\Delta$, even when the actual network delay is $\delta << \Delta$. This raises the question of...

The standard notion of security for threshold signature schemes is static security, where the set of corrupt parties is assumed to be fixed before protocol execution. In this model, the adversary may corrupt up to t−1 out of a threshold of t parties. A stronger notion of security for threshold signatures considers an adaptive adversary, who may corrupt parties dynamically based on its view of the protocol execution, learning the corrupted parties’ secret keys as well as their states....

Secret sharing is a foundational cryptographic primitive for sharing secret keys in distributed systems. In a classical threshold setting, it involves a dealer who has a secret, a set of $n$ users to whom shares of the secret are sent, and a threshold $t$ which is the minimum number of shares required to recover the secret. These schemes offer an all-or-nothing security approach where less than $t$ shares reveal no information about the secret. But these guarantees are threatened by...

Poseidon and Poseidon2 are cryptographic hash functions designed for efficient zero-knowledge proof protocols and have been widely adopted in Ethereum applications. To encourage security research, the Ethereum Foundation announced a bounty program in November 2024 for breaking the Poseidon challenges, i.e. solving the CICO (Constrained Input, Constrained Output) problems for round-reduced Poseidon constructions. In this paper, we explain how to apply the Graeffe transform to univariate...

In this work, we investigate the security assumptions required to prove the adaptive security of threshold signatures. Adaptive security is a strong notion of security that allows an adversary to corrupt parties at any point during the execution of the protocol, and is of practical interest due to recent standardization efforts for threshold schemes. Towards this end, we give two different impossibility results. We begin by formalizing the notion of a key-unique threshold signature...

This paper explores the algebraic structure of the Poseidon and Poseidon2 permutations over NTT-friendly finite fields, with a focus on preimage recovery via root-finding techniques. We introduce an algorithm for efficiently identifying single roots of high-degree univariate polynomials that emerge from these constructions, based on the Graeffe transform and the tangent Graeffe method. Our approach is evaluated on reduced-round bounty instances of these permutations at various security...

A multi-valued broadcast protocol allows a sender $P_s$ to broadcast an $\ell$-bit message $m$ to $n$ recipients. For all relevant models, multi-valued broadcast protocols with asymptotically optimal communication complexity $\mathcal{O}(\ell n)+\mathrm{Poly}(n)$ have been published. Despite their very low communication complexity, these protocols perform poorly in modern networks. Even if the network allows all $n$ parties to send messages at the same time, the execution time of the...

Meme tokens represent a distinctive asset class within the cryptocurrency ecosystem, characterized by high community engagement, significant market volatility, and heightened vulnerability to market manipulation. This paper introduces an innovative approach to assessing liquidity risk in meme token markets using entity-linked address identification techniques. We propose a multi-dimensional method integrating fund flow analysis, behavioral similarity, and anomalous transaction detection to...

Private set intersection (PSI) is a well-researched cryptographic primitive that allows two parties to compute the intersection of their input sets without revealing any information about items outside of the intersection. Fuzzy private set intersection is a relatively new variant of PSI, where items are not matched exactly but ``fuzzily''. Most commonly, items are points $\mathbf{q},\mathbf{w}$ in $d$-dimensional integer space $\mathbb{Z}^d$ and a point is a fuzzy match to another if it...

Hash-based signatures have been studied for decades and have recently gained renewed attention due to their post-quantum security. At the core of the most prominent hash-based signature schemes, XMSS and SPHINCS+, lies a one-time signature scheme based on hash chains due to Winternitz. In this scheme, messages are encoded into vectors of positions (i.e., vertices in a hypercube) in the hash chains, and the signature contains the respective chain elements. The encoding process is crucial for...

A decentralized storage network (DSN) enables clients to delegate data to servers, which retain custody of it for a jointly agreed contract period. While existing constructions employ proof-of-replication (PoRep) iteratively to provide verifiable guarantees during this period, the original security model of PoRep does not account for the blockchain being used as external storage that records prior PoRep proofs, leaving room for adaptive attacks. Similar concerns arise during data retrieval,...

Homomorphic Encryption (HE) is a fundamental Privacy-Enhancing Technology (PET) that enables computations on encrypted data without decryption. Despite its utility, designing an efficient and secure HE scheme is highly complex, requiring sophisticated cryptographic techniques. This paper introduces a novel approach to achieving homomorphic properties—supporting either one addition or one multiplication—within composite groups. While the proposed technique exhibits one-wayness, it has a good...

We introduce a unified approach to quantum cryptanalysis that reduces all \emph{standard abelian hidden subgroup problems} (SAHSPs), including integer factorization, discrete logarithm in finite fields (DLP), and discrete logarithm on elliptic curves, to a single core problem: the \emph{elliptic curve discrete logarithm problem} (ECDLP). This reduction forms the foundation of a framework for quantum cryptanalysis based on ECDLP. At the core of this framework is a \emph{semi-agnostic...

As a theoretical cornerstone of post-quantum cryptography, the Learning With Errors (LWE) problem serves as the security foundation for standardized algorithms such as Kyber and Dilithium. Recently, a framework for provable dual attacks on LWE has been proposed by Pouly et al. in Eurocrypt 2024, addressing the limitations in effectiveness caused by existing methods' reliance on heuristic assumptions in LWE dual attacks. Their paper also poses an open problem on how to formally integrate...

Multi-signatures over pairing-free cyclic groups have seen significant advancements in recent years, including achieving two-round protocols and supporting key aggregation. Key aggregation enables the combination of multiple public keys into a single succinct aggregate key for verification and has essentially evolved from an optional feature to a requirement. To enhance the concrete security of two-round schemes, Pan and Wagner (Eurocrypt 2023, 2024) introduced the first tightly secure...

Attribute-based encryption (ABE) enables fine-grained access control but traditionally depends on a central authority to issue decryption keys. Key-policy registered ABE removes this trust assumption by letting users generate their own keys and register public keys with an untrusted curator, who aggregates them into a compact master public key for encryption. In this paper, we propose a black-box construction of key-policy registered attribute-based encryption from lattice assumptions in...

Masking is one of the most prevalent and investigated countermeasures against side-channel analysis. As an alternative to the simple (e.g., additive) encoding function of Boolean masking, a collection of more algebraically complex masking types has emerged. Recently, inner product masking and the more generic code-based masking have proven to enable higher theoretical security properties than Boolean masking. In CARDIS 2017, Poussier et al. connected this ``security order amplification''...

One approach to solving polynomial systems is to multiply each equation by monomials, which creates a larger system with the coefficient matrix known as the Macaulay matrix. The eXtended Linearization (XL) method, introduced by Courtois, Klimov, Patarin, and Shamir in 2000, is one such approach and includes a sub-algorithm that performs Gaussian elimination on the Macaulay matrix. Due to the simplicity of the method, several improvements and variations have been proposed since its...

One-way functions (OWFs) form the foundation of modern cryptography, yet their unconditional existence remains a major open question. In this work, we study this question by exploring its relation to lossy reductions, i.e., reductions $R$ for which it holds that $I(X;R(X)) \ll n$ for all distributions $X$ over inputs of size $n$. Our main result is that either OWFs exist or any lossy reduction for any promise problem $\Pi$ runs in time $2^{\Omega(\log\tau_\Pi / \log\log n)}$, where...

Side-channel analysis recovers a secret by exploiting the key-dependent characteristics of the leakages. Practical techniques, such as Distance-of-Means analysis (DoM), Kolmogorov-Smirnov analysis (KSA) and Cramér-von Mises analysis (CvMA), provide valuable insights about the secret from the indirect perspectives of statistical moment and cumulative distribution function (CDF) respectively, circumventing the direct and costly estimation of leakage probability densities and therefore enabling...

We show that concrete hardness assumptions about learning or cloning the output state of a random quantum circuit can be used as the foundation for secure quantum cryptography. In particular, under these assumptions we construct secure one-way state generators (OWSGs), digital signature schemes, quantum bit commitments, and private key encryption schemes. We also discuss evidence for these hardness assumptions by analyzing the best-known quantum learning algorithms, as well as proving...

In this paper, we focus on SM4, a widely used and standardized Chinese block cipher. After revisiting the previously proposed optimal 19-round differential characteristic, we observe that its applicability in differential attacks is limited by a reduced pre-sieving probability, causing the time complexity to exceed that of brute force. To overcome this issue, we employ an automated search approach to identify more promising optimal 19-round differential characteristics. By translating key...

This paper examines how quantum computing enhances the encryption system. It studies the relationship between cryptography and quantum physics. The paper considers the historical progression of encryption techniques paying attention to the altering nature of security challenges. Moreover, it analyzes the basic principles of quantum computing, describing its theoretical concept and its advantages over classical systems in terms of potential performance. Also, it focuses on an in-depth...

Safety and liveness are the two classical security properties of consensus protocols. Recent works have strengthened safety with accountability: should any safety violation occur, a sizable fraction of adversary nodes can be proven to be protocol violators. This paper studies to what extent analogous accountability guarantees are achievable for liveness. To reveal the full complexity of this question, we introduce an interpolation between the classical synchronous and partially-synchronous...

Asynchronous Complete Secret Sharing (ACSS) is a foundational module for asynchronous networks, playing a critical role in cryptography. It is essential for Asynchronous Secure Multi-Party Computation (AMPC) and, with termination, is widely applied in Validated Asynchronous Byzantine Agreement (VABA) and Asynchronous Distributed Key Generation (ADKG) to support secure distributed systems. Currently, there are relatively few statistical secure ACSS protocols that can guarantee termination,...

Quantum computing is regarded as one of the most significant upcoming advancements in computer science. Although fully operational quantum computers have yet to be realized, they are expected to solve specific problems that are difficult to solve using classical computers. Given the limitations of quantum computing resources, it is crucial to design compact quantum circuits for core operations, such as quantum arithmetic. In this paper, we focus on optimizing the circuit depth of...

eIDAS 2.0 (electronic IDentification, Authentication and trust Services) is a very ambitious regulation aimed at equipping European citizens with a personal digital identity wallet (EU Digital Identity Wallet) on a mobile phone that not only needs to achieve a high level of security, but also needs to be available as soon as possible for a large number of citizens and respect their privacy (as per GDPR - General Data Protection Regulation). In this paper, we introduce the foundations of...