157 citations · 815 across the 35 of their papers we have counts for
28 papers · 1 filter
On The Simplest Quantum-Secure Block Cipher
Gorjan Alagic, Joseph Carolan, Christian Majenz +1
Pseudorandom permutations are ubiquitous in theoretical and applied cryptography. PRPs that offer security even against adversaries making quantum queries are of increasing interes…
Compressed Permutation Oracles Revisited
Joseph Carolan, Christian Majenz
The compressed permutation oracle has been used to analyze the quantum security of a number of cryptographic constructions which resisted prior techniques. However, these analyses…
The Sponge is Quantum Indifferentiable
Gorjan Alagic, Joseph Carolan, Christian Majenz +1
The sponge is a cryptographic construction that turns a public permutation into a hash function. When instantiated with the Keccak permutation, the sponge forms the NIST SHA-3 stan…
Permutation Superposition Oracles for Quantum Query Lower Bounds
Christian Majenz, Giulio Malavolta, Michael Walter
We propose a generalization of Zhandry's compressed oracle method to random permutations, where an algorithm can query both the permutation and its inverse. We show how to use the…
Post-Quantum Security of the Even-Mansour Cipher
Gorjan Alagic, Chen Bai, Jonathan Katz +1
The Even-Mansour cipher is a simple method for constructing a (keyed) pseudorandom permutation from a public random permutation~. It is secur…
Local simultaneous state discrimination
Christian Majenz, Maris Ozols, Christian Schaffner +1
Quantum state discrimination is one of the most fundamental problems studied in quantum information theory. Applications range from channel coding to metrology and cryptography. In…
Limitations on Uncloneable Encryption and Simultaneous One-Way-to-Hiding
Christian Majenz, Christian Schaffner, Mehrdad Tahmasbi
We study uncloneable quantum encryption schemes for classical messages as recently proposed by Broadbent and Lord. We focus on the information-theoretic setting and give several li…
Quantum-access security of the Winternitz one-time signature scheme
Christian Majenz, Chanelle Matadah Manfouo, Maris Ozols
Quantum-access security, where an attacker is granted superposition access to secret-keyed functionalities, is a fundamental security model and its study has inspired results in po…
Tight adaptive reprogramming in the QROM
Alex B. Grilo, Kathrin Hövelmanns, Andreas Hülsing +1
The random oracle model (ROM) enjoys widespread popularity, mostly because it tends to allow for tight and conceptually simple proofs where provable security in the standard model…
Quantum copy-protection of compute-and-compare programs in the quantum random oracle model
Andrea Coladangelo, Christian Majenz, Alexander Poremba
Copy-protection allows a software distributor to encode a program in such a way that it can be evaluated on any input, yet it cannot be "pirated" - a notion that is impossible to a…
Weak approximate unitary designs and applications to quantum encryption
Cécilia Lancien, Christian Majenz
Unitary -designs are the bread and butter of quantum information theory and beyond. An important issue in practice is that of efficiently constructing good approximations of suc…
Efficient simulation of random states and random unitaries
Gorjan Alagic, Christian Majenz, Alexander Russell
We consider the problem of efficiently simulating random quantum states and random unitary operators, in a manner which is convincing to unbounded adversaries with black-box oracle…
Secure Multi-party Quantum Computation with a Dishonest Majority
Yfke Dulek, Alex B. Grilo, Stacey Jeffery +2
The cryptographic task of secure multi-party (classical) computation has received a lot of attention in the last decades. Even in the extreme case where a computation is performed…
Non-malleability for quantum public-key encryption
Christian Majenz, Christian Schaffner, Jeroen van Wier
Non-malleability is an important security property for public-key encryption (PKE). Its significance is due to the fundamental unachievability of integrity and authenticity guarant…
Quantum Lazy Sampling and Game-Playing Proofs for Quantum Indifferentiability
Jan Czajkowski, Christian Majenz, Christian Schaffner +1
Game-playing proofs constitute a powerful framework for non-quantum cryptographic security arguments, most notably applied in the context of indifferentiability. An essential ingre…
Can you sign a quantum state?
Gorjan Alagic, Tommaso Gagliardoni, Christian Majenz
Cryptography with quantum states exhibits a number of surprising and counterintuitive features. In a 2002 work, Barnum et al. argue that these features imply that digital signature…
Constraints on Multipartite Quantum Entropies
Christian Majenz
The von Neumann entropy plays a vital role in quantum information theory. The von Neumann entropy determines, e.g., the capacities of quantum channels. Also, entropies of composite…
Entropy in Quantum Information Theory -- Communication and Cryptography
Christian Majenz
In this Thesis, several results in quantum information theory are collected, most of which use entropy as the main mathematical tool. *While a direct generalization of the Shannon…
Asymptotic performance of port-based teleportation
Matthias Christandl, Felix Leditzky, Christian Majenz +3
Quantum teleportation is one of the fundamental building blocks of quantum Shannon theory. While ordinary teleportation is simple and efficient, port-based teleportation (PBT) enab…
Conditional Decoupling of Quantum Information
Mario Berta, Fernando G. S. L. Brandao, Christian Majenz +1
Insights from quantum information theory show that correlation measures based on quantum entropy are fundamental tools that reveal the entanglement structure of multipartite states…
Quantum-secure message authentication via blind-unforgeability
Gorjan Alagic, Christian Majenz, Alexander Russell +1
Formulating and designing authentication of classical messages in the presence of adversaries with quantum query access has been a longstanding challenge, as the familiar classical…
Unforgeable Quantum Encryption
Gorjan Alagic, Tommaso Gagliardoni, Christian Majenz
We study the problem of encrypting and authenticating quantum data in the presence of adversaries making adaptive chosen plaintext and chosen ciphertext queries. Classically, secur…
Disentanglement Cost of Quantum States
Mario Berta, Christian Majenz
We show that the minimal rate of noise needed to catalytically erase the entanglement in a bipartite quantum state is given by the regularized relative entropy of entanglement. Thi…
Quantum non-malleability and authentication
Gorjan Alagic, Christian Majenz
In encryption, non-malleability is a highly desirable property: it ensures that adversaries cannot manipulate the plaintext by acting on the ciphertext. Ambainis, Bouda and Winter…