Levin and Pedersen proposed at Asiacrypt2025 a new verifiable random function (VRF) based on a CGL-analogue hash function constructed from radical isogenies. Their construction applies the same secret radical-CGL walk to a public starting curve and a message-dependent curve, and uses an R1CS proof relation to show that the two walks use the same secret key. We present a two-stage attack on this construction. The first stage concerns the unspecified representation of the public key. The...

The Unbalanced Oil and Vinegar (UOV) scheme was proposed by Kipnis et al. in 1999 as a multivariate signature scheme. Owing to its small signature size and its resistance to various attacks over more than two decades, UOV has become one of the leading candidates in multivariate public key cryptography. In 2025, Ran proposed a novel algebraic key recovery attack exploiting the algebraic structure of UOV, which reduced the security of several parameter sets of UOV and its variants submitted...

Masking is a widely adopted countermeasure to protect cryptographic implementations from side-channel attacks. Subsequent research has focused on designing masking schemes and formally proving their security, notably through the development of automated tools, within models abstracting the reality of a sidechannel analysis. These designs rely on an external source of randomness; however, there is currently no consensus on the choice of (pseudo-)random number generators for masking. To the...

Designated Verifier Signatures (DVS) are an important variant of digital signatures that ensure only a specified verifier can validate a signature, while preserving non-transferability. With the advent of quantum computing, several quantum DVS schemes have been proposed to achieve quantum security. In this paper, we revisit the quantum DVS protocol of Xin et al. [Quantum Information Processing, 2022] and provide a structural cryptanalysis of its design. We show that the scheme admits an...

Neural differential distinguishers are usually compared at a fixed number of labeled samples. However, different input representations may require different numbers of ciphertexts per sample, making fixed-sample comparisons potentially misleading from a cryptanalytic data-complexity perspective. In this paper, we study neural differential distinguishers under a fixed ciphertext budget. We ask whether the available encryption queries should be spent on more independent plaintext bases, or on...

Witness encryption (WE) allows one party to encrypt a message under an arbitrary satisfiable circuit, so that anyone holding a satisfying input can decrypt. Efficient WE enables numerous modern applications, such as identity-based and attribute-based encryption. Recent candidates for efficient WE base their security on rank properties of structured ciphertext matrices, which encode the validity of a given witness. This shrinks ciphertext sizes considerably compared to previous...

At ITCS 2020, Bartusek, Ishai, Jain, Ma, Sahai, and Zhandry proposed a framework for witness encryption based on affine determinant programs and gave a concrete witness encryption candidate. Yao, Chen, and Yu later broke the separate ADP-based indistinguishability-obfuscation candidate, while noting that their attack did not apply to the witness-encryption construction. More recently, Soukhanov et al. proposed witness encryption from arithmetic affine determinant programs. Soukhanov...

Poseidon is an algebraic permutation designed for efficient use in proof systems. Its nonlinear layer consists of power-map S-boxes. In a full round, the S-box is applied to every state coordinate; in a partial round, it is applied to only one coordinate, reducing the arithmetization cost. Each round also applies an MDS linear layer to diffuse information across the state. To study algebraic degree, we let the input depend on variables and follow the resulting family of states...

This note presents a new unconditional attack on the supersingular isogeny problem, with time and memory complexity $p^{2/5+o(1)}$. It builds on the approach by Eisenträger-Hallgren-Leonardi-Morrison-Park (2020) and Fuselier-Iezzi-Kozek-Morrison-Namoijam (2025), and is related to the recent heuristic attack with complexity $p^{1/3+o(1)}$ by Wesolowski (ePrint 2026/1486): all of these search for a separable isogeny from a curve to its Galois conjugate to form a non-scalar endomorphism. Our...

Conditional linear cryptanalysis represents an extension of linear cryptanalysis and has been applied to DES and AES. Notably, it enables the construction of a linear distinguisher for 4-round AES, which is considered unattainable through standard linear cryptanalysis. The underlying principle is that the correlation of a linear approximation can be improved when the data is restricted to a specific subspace or subset, thereby allowing more effective linear cryptanalysis. The critical...

Let $E=\mathbb Q(\zeta_m)$ be a power-of-two cyclotomic field, with maximal totally real subfield $K=\mathbb Q(\zeta_m+\zeta_m^{-1})$. In previous work, Chevignard et al. (Eurocrypt'25) gave a reduction from module-LIP for rank-two module lattices over $\mathcal O_E$ to the norm-reduced Principal Ideal Problem (nrdPIP) in a quaternion algebra. We derive two consequences of this reduction. First, we obtain a polynomial time reduction from rank-$2$ module-LIP over $\mathcal O_E$ to rank-$3$...

${\sharp}\textrm{Pencil}$ is a domain-extended pseudorandom function by Bhaumik et al, accepted at CRYPTO 2026, with a claim that it achieves close to $n$-bit security beyond the birthday bound. It is used as the key-derivation layer of the ${\sharp}\textrm{Pencil}$-CAU authenticated-encryption mode. We show that ${\sharp}\textrm{Pencil}$ has a birthday-bound collision attack: its front end $\textsf{Sharp}$ compresses the second half $N_2$ of the input through the $(n-8)$-bit...

In this work, we propose three techniques for advancing cryptanalysis of round-reduced AES, two of which exploit the multiplicative inverse, and a third, structural, property that generalizes the S-box switch to multiple quartets. Firstly, we formalize the cross-ratio property for tracing a nonlinear equation over $F_{2^8}$ from the differences of four distinct inputs or their respective outputs through the key-wrapped multiplicative inverse. While the underlying properties of the...

Post-Quantum Cryptography is now in its deployment phase. Amongst the threats encountered in real-world applications is Side Channel Analysis, a cryptanalysis branch relying on the study of physical leakages from unsecured implementations. However, the FALCON post-quantum signature includes non-linear functions on real numbers, and applying the generic masking countermeasure to these functions has only been recently studied. In this work, we use convergent sequences to approximate the...

Neural differential distinguishers have become an active research direction in​ symmetric-key cryptanalysis since the introduction of deep-learning-based attacks on​ round-reduced SPECK. Early neural distinguishers typically used a single ciphertext pair​ or ciphertext difference as input. Recent studies, however, show that richer input​ representations can substantially affect the information available to the classifier, the data​ cost of each labeled sample, and the relevance of the...

In AfricaCrypt 2025, Seck et al. proposed a new generalized Wiener-type attack on an RSA-like cryptosystem proposed by Cotan and Teseleanu (NordSec 2023). In their attack, they studied the generalized key equation $eu - (p^4 - 1)(q^4 - 1)v = w$ and showed that a private exponent $d$ which is too large or too small can be recovered in polynomial time. Another RSA variant based on cubic Pell curves with key equation $ed - (p - 1)^2(q - 1)^2 k = 1$, was examined by Rahmani and Nitaj in...

Hybrid fully homomorphic encryption (FHE) inference improves the practicality of private inference by letting the server evaluate linear layers homomorphically while the client decrypts and applies nonlinearities. Recent schemes attempt to protect model confidentiality by returning noisy, output-permuted responses and appealing to shuffle-model differential privacy (DP). We show that this protection fails in the correctness regime required by hybrid FHE systems. For a $d$-input linear layer,...

The Signal Protocol’s Double Ratchet and X3DH/PQXDH handshakes give in-transit messages forward secrecy and post-compromise security: compromising a session key does not expose past traffic, and the protocol self-heals after a fresh Diffie–Hellman step. Encrypted backups, by contrast, are commonly protected by a single static secret, a “Backup Recovery Key” generated once and held constant until manually rotated. We show, with an explicit attack, that this baseline design provably fails even...

Almost fifty years after its introduction, the McEliece cryptosystem occupies an unusual place in the post-quantum landscape. Its public keys are far larger than those of most competing schemes, its original parameters no longer provide adequate security, and several compact variants proposed to reduce key size have subsequently been broken. Nevertheless, the binary Goppa-code foundation retained in Classic McEliece continues to resist known practical attacks for the selected Classic...

Standard Tseitin encodings of the SHA-256 nonlinear functions Ch and Maj can hide conditioned differential projections from Boolean Constraint Propagation (BCP). We materialize them as short, semantically redundant CNF clauses. A cofactor theorem characterizes all controlled differential linear forms; its implemented unit-vector specialization returns exactly all minimum-control projections, yielding four Ch and twelve Maj clauses per bit. The clauses preserve models, introduce no variables,...

We prove that under a plausible heuristic assumption (on the smoothness of certain random integers), the supersingular isogeny problem can be solved in time and memory $p^{1/3 + o(1)}$. This improves upon the previous best complexity of $p^{1/2} \cdot(\log p)^{O(1)}$. This problem is arguably the central hard problem underlying isogeny-based cryptography, and the cost of its resolution is a major (and often the only) factor in the choice of secure parameters. The impact on concrete...

In secret-key private information retrieval, a client with a short secret key retrieves a database item while hiding the requested index, and possibly also the database, from the server. The server answers using an encoded version of the database, generated via one-time preprocessing. Secret-key PIR provides an attractive "stateless" alternative to stateful PIR and oblivious RAM, and can be viewed as strengthening the standard notion of searchable symmetric encryption by not allowing any...

Boomerang cryptanalysis is inherently a four-point phenomenon, yet its recent geometric formulation relies on a 3-wise representation imposed by a quartet-sum-zero assumption. This simplification makes the transition matrices tractable, but it also removes boomerangs with unequal paired differences and prevents the framework from modeling impossible boomerang distinguishers. We propose an exact 4-wise geometric framework for boomerang cryptanalysis that is a \emph{strict generalization}...

We give a structural cryptanalysis of GRAFHEN, a proposed group-based fully homomorphic encryption scheme whose public rewriting rules hide a group representation used for decryption. Under the designers' isomorphism hypothesis, the compatible representations in a finite target $T$ form one free $\mathrm{Aut}(T)$-orbit. Thus every representative induces the same zero predicate. For a fixed publication, the published key-class expression is the expected trial count of uniform verified...