The Feistel structure represents a fundamental architectural component within the domain of symmetric cryptographic algorithms, with a substantial body of research conducted within the context of classical computing environments. Nevertheless, research into specific symmetric cryptographic algorithms utilizing the Feistel structure is relatively scarce in quantum computing environments. This paper builds upon a novel 4-round distinguisher proposed by Ito et al. for the Feistel structure...

This paper presents quantum algorithms for fast correlation attacks, one of the most powerful techniques for cryptanalysis on LFSR-based stream ciphers in the classical setting. Typical fast correlation attacks recover a value related to the initial state of the underlying LFSR by solving a decoding problem on a binary linear code with the Fast Walsh-Hadamard Transform (FWHT). Applying the FWHT on a function in the classical setting is mathematically equivalent to applying the Hadamard...

QCB is a proposal for a post-quantum secure, rate-one authenticated encryption with associated data scheme (AEAD) based on classical OCB3 and \(\Theta\)CB, which are vulnerable against a quantum adversary in the Q2 setting. The authors of QCB prove integrity under plus-one unforgeability, whereas the proof of the stronger definition of blind unforgeability has been left as an open problem. After a short overview of QCB and the current state of security definitions for authentication, this...

In post-quantum cryptography, hash-based signature schemes are attractive choices because of the weak assumptions. Most existing hash-based signature schemes are proven secure against post-quantum chosen message attacks (CMAs), where the adversaries are able to execute quantum computations and classically query to the signing oracle. In some cases, the signing oracle is also considered quantum-accessible, meaning that the adversaries are able to send queries with superpositions to the...

We study quantum superposition attacks against permutation-based pseudorandom cryptographic schemes. We first extend Kuwakado and Morii's attack against the Even-Mansour cipher (ISITA 2012), and exhibit key recovery attacks against a large class of pseudorandom schemes based on a single call to an $n$-bit permutation, with polynomial $O(n)$ quantum steps. We also show how to overcome restrictions on available quantum data in certain relevant settings. We then consider TPPR schemes, namely,...

We proposed three general frameworks F1,F2, and F3 for n-to-n-bit PRFs with one, two parallel, and two serial public permutation calls respectively, where every permutation is preceded and followed by any bitwise linear mappings. We analyze them in the Q2 model where attackers have quantum-query access to PRFs and permutations. Our results show F1 is not secure with O(n) quantum queries while its PRFs achieve n/2-bit security in the classical setting, and F2,F3 are not secure with...

We systematically study the security of twelve Beyond-Birthday-Bound Message Authentication Codes (BBB MACs) in the Q2 model where attackers have quantum-query access to MACs. Assuming the block size of the underlying (tweakable) block cipher is $n$ bits, the security proofs show that they are secure at least up to $\mathcal{O}(2^ {2n/3}) $ queries in the classical setting. The best classical attacks need $\mathcal{O}(2^ {3n/4}) $ queries. We consider secret state recovery against...

In most post-quantum signature protocols, the verification procedure leaks information about which signature is being verified, and/or which public key is being used to verify the signature, to timing and other side-channel attacks. In some applications, this information leak is a breach of user privacy or system security. One class of signature protocols, based on the parallel composition of many runs of one or more interactive cut-and-choose protocols, can be modified to enable...

In this work we study the quantum security of public key encryption schemes (PKE). Boneh and Zhandry (CRYPTO'13) initiated this research area for PKE and symmetric key encryption (SKE), albeit restricted to a classical indistinguishability phase. Gagliardoni et al. (CRYPTO'16) advanced the study of quantum security by giving, for SKE, the first definition with a quantum indistinguishability phase. For PKE, on the other hand, no notion of quantum security with a quantum indistinguishability...

Following recent comments in a NIST document related to threshold cryptographic standards, we examine the case of thresholdizing the HashEdDSA signature scheme. This is a deterministic signature scheme based on Edwards elliptic curves. Unlike DSA, it has a Schnorr like signature equation, which is an advantage for threshold implementations, but it has the disadvantage of having the ephemeral secret obtained by hashing the secret key and the message. We show that one can obtain relatively...

Abelian secret sharing schemes (SSS) are generalization of multi-linear SSS and similar to them, abelian schemes are homomorphic. There are numerous results on linear and multi-linear SSSs in the literature and a few ones on homomorphic SSSs too. Nevertheless, the abelian schemes have not taken that much attention. We present three main results on abelian and homomorphic SSSs in this paper: (1) abelian schemes are more powerful than multi-linear schemes (we achieve a constant factor...

This paper shows that quantum computers can significantly speed-up a type of meet-in-the-middle attacks initiated by Demiric and Selçuk (DS-MITM attacks), which is currently one of the most powerful cryptanalytic approaches in the classical setting against symmetric-key schemes. The quantum DS-MITM attacks are demonstrated against 6 rounds of the generic Feistel construction supporting an $n$-bit key and an $n$-bit block, which was attacked by Guo et al. in the classical setting with data,...

A multiparty computation (MPC) protocol allows a set of players to compute a function of their inputs while keeping the inputs private and at the same time securing the correctness of the output. Most MPC protocols assume that the adversary can corrupt up to a fixed fraction of the number of players. Hirt and Maurer initiated the study of MPC under more general corruption patterns, in which the adversary is allowed to corrupt any set of players in some pre-defined collection of sets [6]. In...