Unclonable Encryption in the Haar Random Oracle Model
This provides the first evidence for the existence of reusable unclonable encryption in a theoretical 'micocrypt' world, addressing a foundational challenge in cryptography.
The paper tackles the problem of constructing unclonable encryption in a model where one-way functions might not exist, achieving a scheme with unclonable indistinguishability security, reusable secret keys, and support for arbitrary-length messages.
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.