Unclonable Encryption, Revisited

Unclonable encryption, introduced by Broadbent and Lord (TQC’20), is an encryption scheme with the following attractive feature: given a ciphertext, adversary cannot create two ciphertexts both of which decrypt to same message as original ciphertext.We revisit this notion show following: 1. Reusability: The constructions proposed have disadvantage that they either guarantee one-time security (that is, key can only be used once encrypt message) in plain model or guaranteed random oracle model. We construct unclonable schemes semantic security. present from minimal cryptographic assumptions: (i) private-key assuming post-quantum one-way functions and, (ii) public-key scheme. 2. Lower Bound Generalized Construction: information-theoretic secure construction Lord. success probability their was \(0.85^n\), where n length message. It interesting understand whether ideal (negligibly close to) \(0.5^n\) unattainable. generalize based on broader class monogamy entanglement games (while BB84 game). demonstrate simple cloning attack succeeds \(0.71^n\) against including also \(0.75^n\) exclusively 3. Implication Copy-Protection: satisfying stronger property, called unclonable-indistinguishability (defined Lord), implies copy-protection for unlearnable functions. While we currently don’t implication demonstrates new path copy-protection.