Papers
Topics
Authors
Recent
Assistant
AI Research Assistant
Well-researched responses based on relevant abstracts and paper content.
Custom Instructions Pro
Preferences or requirements that you'd like Emergent Mind to consider when generating responses.
Gemini 2.5 Flash
Gemini 2.5 Flash 78 tok/s
Gemini 2.5 Pro 52 tok/s Pro
GPT-5 Medium 24 tok/s Pro
GPT-5 High 26 tok/s Pro
GPT-4o 120 tok/s Pro
Kimi K2 193 tok/s Pro
GPT OSS 120B 459 tok/s Pro
Claude Sonnet 4.5 36 tok/s Pro
2000 character limit reached

Black-Box Separation Between Pseudorandom Unitaries, Pseudorandom Isometries, and Pseudorandom Function-Like States (2510.04486v1)

Published 6 Oct 2025 in quant-ph

Abstract: Pseudorandom functions (PRFs) are one of the most fundamental primitives in classical cryptography. On the other hand, in quantum cryptography, it is possible that PRFs do not exist but their quantum analogues could exist, and still enabling many applications including SKE, MACs, commitments, multiparty computations, and more. Pseudorandom unitaries (PRUs) [Ji, Liu, Song, Crypto 2018], pseudorandom isometries (PRIs) [Ananth, Gulati, Kaleoglu, Lin, Eurocrypt 2024], and pseudorandom function-like state generators (PRFSGs) [Ananth, Qian, Yuen, Crypto 2022] are major quantum analogs of PRFs. PRUs imply PRIs, and PRIs imply PRFSGs, but the converse implications remain unknown. An important open question is whether these natural quantum analogues of PRFs are equivalent. In this paper, we partially resolve this question by ruling out black-box constructions of them: 1. There are no black-box constructions of $O(\log\lambda)$-ancilla PRUs from PRFSGs. 2. There are no black-box constructions of $O(\log\lambda)$-ancilla PRIs with $O(\log\lambda)$ stretch from PRFSGs. 3. There are no black-box constructions of $O(\log\lambda)$-ancilla PRIs with $O(\log\lambda)$ stretch from PRIs with $\Omega(\lambda)$ stretch. Here, $O(\log\lambda)$-ancilla means that the generation algorithm uses at most $O(\log\lambda)$ ancilla qubits. PRIs with $s(\lambda)$ stretch is PRIs mapping $\lambda$ qubits to $\lambda+s(\lambda)$ qubits. To rule out the above black-box constructions, we construct a unitary oracle that separates them. For the separations, we construct an adversary based on the quantum singular value transformation, which would be independent of interest and should be useful for other oracle separations in quantum cryptography.

Summary

We haven't generated a summary for this paper yet.

Lightbulb Streamline Icon: https://streamlinehq.com

Continue Learning

We haven't generated follow-up questions for this paper yet.

List To Do Tasks Checklist Streamline Icon: https://streamlinehq.com

Collections

Sign up for free to add this paper to one or more collections.