34 citations · 77 across the 13 of their papers we have counts for
15 papers
Computational Work Extraction: The Complexity of Catalysts
Atul Singh Arora, Shantanav Chakraborty, Alexandru Cojocaru +2
We prove maximal separations: -qubit systems can have ergotropy, while every efficient process extracts negligible work, even for Hamiltonians consisting of single-qubit…
Eavesdropper-Blind Remote State Preparation and Applications to Quantum Public-Key Encryption
Kaniuar Bacho, Alexandru Cojocaru
Remote state preparation (RSP) is a central primitive in quantum cryptography, enabling classical parties to remotely construct quantum states using only classical communication. A…
Equivalence Between Average-Case Hardness of Learning and Cryptography for Mixed Quantum States
Alexandru Cojocaru, Laura Lewis
The relationship between cryptography and learning theory has long been a central theme in the foundations of theoretical computer science: cryptographic primitives can imply hardn…
Verified Pythagorean Composition for Adaptive Cryptographic Games: Noise Flooding in Homomorphic Encryption
Yi Lee, Alexandru Cojocaru, Junyi Liu +1
Noise flooding is a standard defense against decryption attacks on approximate homomorphic encryption, but its security proof is unusually sensitive to composition. Replacing each…
NISQ Security and Complexity via Simple Classical Reasoning
Alexandru Cojocaru, Juan Garay, Qipeng Liu +1
We give novel lifting theorems for security games in the quantum random oracle model (QROM) in Noisy Intermediate-Scale Quantum (NISQ) settings such as the hybrid query model, the…
Improved Quantum Lifting by Coherent Measure-and-Reprogram
Alexandru Cojocaru, Juan Garay, Qipeng Liu +1
We give a tighter lifting theorem for security games in the quantum random oracle model. At the core of our main result lies a novel measure-and-reprogram framework that we call co…
Quantum Lifting for Invertible Permutations and Ideal Ciphers
Alexandru Cojocaru, Minki Hhan, Qipeng Liu +2
In this work, we derive the first lifting theorems for establishing security in the quantum random permutation and ideal cipher models. These theorems relate the success probabilit…
A computational test of quantum contextuality, and even simpler proofs of quantumness
Atul Singh Arora, Kishor Bharti, Alexandru Cojocaru +1
Bell non-locality is a fundamental feature of quantum mechanics whereby measurements performed on "spatially separated" quantum systems can exhibit correlations that cannot be unde…
Generalized Hybrid Search and Applications to Blockchain and Hash Function Security
Alexandru Cojocaru, Juan Garay, Fang Song
In this work we first examine the hardness of solving various search problems by hybrid quantum-classical strategies, namely, by algorithms that have both quantum and classical cap…
Quantum Multi-Solution Bernoulli Search with Applications to Bitcoin's Post-Quantum Security
Alexandru Cojocaru, Juan Garay, Aggelos Kiayias +2
A proof of work (PoW) is an important cryptographic construct enabling a party to convince others that they invested some effort in solving a computational task. Arguably, its main…
Secure Two-Party Quantum Computation Over Classical Channels
Michele Ciampi, Alexandru Cojocaru, Elham Kashefi +1
Secure two-party computation considers the problem of two parties computing a joint function of their private inputs without revealing anything beyond the output. In this work, we…
Security Limitations of Classical-Client Delegated Quantum Computing
Christian Badertscher, Alexandru Cojocaru, Léo Colisson +4
Secure delegated quantum computing allows a computationally weak client to outsource an arbitrary quantum computation to an untrusted quantum server in a privacy-preserving manner.…
QFactory: classically-instructed remote secret qubits preparation
Alexandru Cojocaru, Léo Colisson, Elham Kashefi +1
The functionality of classically-instructed remotely prepared random secret qubits was introduced in (Cojocaru et al 2018) as a way to enable classical parties to participate in se…
On the possibility of classical client blind quantum computing
Alexandru Cojocaru, Léo Colisson, Elham Kashefi +1
We define the functionality of delegated pseudo-secret random qubit generator (PSRQG), where a classical client can instruct the preparation of a sequence of random qubits at some…
Complexity-theoretic limitations on blind delegated quantum computation
Scott Aaronson, Alexandru Cojocaru, Alexandru Gheorghiu +1
Blind delegation protocols allow a client to delegate a computation to a server so that the server learns nothing about the input to the computation apart from its size. For the sp…