Proofs of No Intrusion
Vipul Goyal, Justin Raizes
TL;DR
The work defines Proofs of No-Intrusion (PoNIs), interactive protocols allowing a classical client to verify that a quantum server storing data has not leaked usable information without destroying the data. It develops PoNIs for coset states and shows how to extend them to encryption under Fully Homomorphic Encryption and to unclonable primitives like decryption keys and signature tokens under weaker assumptions via Oblivious State Preparation. The constructions bridge cloning-based security (coset-state unclonability) with practical cryptographic tasks, including certified deletion analogues and composable security notions, and they discuss decisional versus search-based security in this quantum setting. The results enable non-destructive, repeatable testing of data integrity in quantum-outsource scenarios and illuminate pathways to lighter-weight PoNIs compared with prior unclonable-cryptography techniques by leveraging weaker assumptions such as LWE-based coset-state tests and OSP-based protocols.
Abstract
A central challenge in data security is not just preventing theft, but detecting whether it has occurred. Classically, this is impossible because a perfect copy leaves no evidence. Quantum mechanics, on the other hand, forbids general duplication, opening up new possibilities. We introduce Proofs of No Intrusion, which enable a classical client to remotely test whether a quantum server has been hacked and the client's data stolen. Crucially, the test does not destroy the data being tested, avoiding the need to store a backup elsewhere. We define and construct proofs of no intrusion for ciphertexts assuming fully homomorphic encryption. Additionally, we show how to equip several constructions of unclonable primitives with proofs of non-intrusion, such as unclonable decryption keys and signature tokens. Conceptually, proofs of non-intrusion can be defined for essentially any unclonable primitive. At the heart of our techniques is a new method for non-destructively testing coset states with classical communication. It can be viewed as a non-destructive proof of knowledge of a measurement result of the coset state.