How to Copy-Protect Malleable-Puncturable Cryptographic Functionalities Under Arbitrary Challenge Distributions

2025-07-25

AI Summary

This work addresses quantum copy protection for extensible-deletable cryptographic functionalities, overcoming key limitations of prior schemes—namely, reliance on pseudorandom deletion points and restricted challenge distributions. We formally define the class of extensible-deletable cryptographic schemes and propose a novel security framework integrating quantum copy protection with cryptographic deletion techniques, enabling rigorous security proofs under arbitrary high-entropy challenge distributions. Our contributions are threefold: (1) a more expressive functional abstraction that eliminates dependence on fixed deletion points; (2) the first generic copy-protection paradigm tailored to broadly defined deletable functionalities; and (3) a substantial expansion of the set of cryptographic functionalities amenable to secure quantum copy protection. This advances the theoretical foundations for privacy-enhancing cryptographic systems.

Technology Category

• Machine Learning: Quantum Machine Learning
• Game Theory and Economic Paradigms: Cooperative Game Theory
• Computer Vision: Adversarial Attacks & Robustness

Application Category

• Security and Privacy: Applications of cryptography
• Responsible Web: Measurement, analysis, and circumvention of Web censorship
• Search and Retrieval-Augmented AI: Web learning to rank, online learning, and counterfactual learning for ranking

Abstract

A quantum copy-protection scheme (Aaronson, CCC 2009) encodes a functionality into a quantum state such that given this state, no efficient adversary can create two (possibly entangled) quantum states that are both capable of running the functionality. There has been a recent line of works on constructing provably-secure copy-protection schemes for general classes of schemes in the plain model, and most recently the recent work of Çakan and Goyal (IACR Eprint, 2025) showed how to copy-protect all cryptographically puncturable schemes with pseudorandom puncturing points. In this work, we show how to copy-protect even a larger class of schemes. We define a class of cryptographic schemes called malleable-puncturable schemes where the only requirement is that one can create a circuit that is capable of answering inputs at points that are unrelated to the challenge in the security game but does not help the adversary answer inputs related to the challenge. This is a flexible generalization of puncturable schemes, and can capture a wide range of primitives that was not known how to copy-protect prior to our work. Going further, we show that our scheme is secure against arbitrary high min-entropy challenge distributions whereas previous work has only considered schemes that are punctured at pseudorandom points.

Problem

• Copy-protect malleable-puncturable cryptographic functionalities
• Secure against arbitrary challenge distributions
• Generalize puncturable schemes for broader applicability

Innovation

• Quantum copy-protection for malleable-puncturable schemes
• Secure against arbitrary high min-entropy distributions
• Generalizes puncturable schemes for broader applicability