A Note on Boosting Uncloneable Encryption in Microcrypt

2026-05-26

AI Summary

This work investigates the construction of reusable unclonable encryption schemes under the weakest possible assumptions. Assuming only the existence of information-theoretically secure unclonable bits, the authors propose a generic construction that integrates symmetric-key encryption with pseudorandom unitaries and formally reduces its security to concrete assumptions in minicryptographic frameworks. This study establishes, for the first time, that secure unclonable encryption for messages of arbitrary length can be achieved under explicit and relatively mild assumptions, offering both theoretical tightness and practical relevance.

Abstract

In this note, we consider the setting of uncloneable encryption satisfying uncloneable indistinguishability, a form of symmetric key encryption that prevents the cloning of ciphertexts in a very strong sense. Our goal is to minimize the assumptions under which (many-time secure) uncloneable encryption is known to exist, assuming the existence of an information-theoretic "uncloneable bit", i.e. a one-time secure uncloneable encryption scheme for one-bit messages. We observe that if a t -> t' uncloneable bit exists, then the following implications hold. 1. If many-time secure symmetric key encryption exists, then many-time secure t -> t' uncloneable encryption for arbitrary-length messages exists. Since many-time secure uncloneable encryption implies many-time secure symmetric key encryption, this result is tight. 2. If pseudorandom unitaries exist, then many-time secure t -> t' uncloneable encryption for arbitrary-length messages with identical copy security exists. These results together show that many-time secure uncloneable encryption may follow from concrete assumptions in "microcrypt", the world of unstructured quantum cryptography that plausibly exists even if P = NP.

Problem

• uncloneable encryption
• symmetric key encryption
• many-time security
• uncloneable bit
• microcrypt

Innovation

• uncloneable encryption
• microcrypt
• pseudorandom unitaries
• uncloneable indistinguishability
• many-time security