Unclonable Encryption in the Haar Random Oracle Model

TL;DR

This paper introduces a novel unclonable encryption scheme in the Haar random oracle model, supporting reusable keys and arbitrary message lengths, providing evidence for its existence under minimal assumptions.

Contribution

It constructs the first reusable unclonable encryption scheme in a minimal assumption setting using Haar random oracles.

Findings

Supports reuse of secret keys.

Encrypts arbitrary-length messages.

Introduces a new unitary reprogramming lemma.

Abstract

We construct unclonable encryption (UE) in the Haar random oracle model, where all parties have query access to $U,U^\dagger,U^*,U^T$ for a Haar random unitary $U$. Our scheme satisfies the standard notion of unclonable indistinguishability security, supports reuse of the secret key, and can encrypt arbitrary-length messages. That is, we give the first evidence that (reusable) UE, which requires computational assumptions, exists in "micocrypt", a world where one-way functions may not exist. As one of our central technical contributions, we build on the recently introduced path recording framework to prove a natural ``unitary reprogramming lemma'', which may be of independent interest.