A Modular Approach to Unclonable Cryptography

We explore a new pathway to designing unclonable cryptographic primitives. We propose a new notion called unclonable puncturable obfuscation (UPO) and study its implications for unclonable cryptography. Using UPO, we present modular (and in some cases, arguably, simple) constructions of many primitives in unclonable cryptography, including, public-key quantum money, quantum copy-protection for many classes of functionalities, unclonable encryption, and single-decryption encryption. Notably, we obtain the following new results assuming the existence of UPO:We show that any cryptographic functionality can be copy-protected as long as it satisfies a notion of security, which we term puncturable security. Prior feasibility results focused on copy-protecting specific cryptographic functionalities.We show that copy-protection exists for any class of evasive functions as long as the associated distribution satisfies a preimage-sampleability condition. Prior works demonstrated copy-protection for point functions, which follows as a special case of our result. We show that any cryptographic functionality can be copy-protected as long as it satisfies a notion of security, which we term puncturable security. Prior feasibility results focused on copy-protecting specific cryptographic functionalities. We show that copy-protection exists for any class of evasive functions as long as the associated distribution satisfies a preimage-sampleability condition. Prior works demonstrated copy-protection for point functions, which follows as a special case of our result. We put forward two constructions of UPO. The first construction satisfies two notions of security based on the existence of (post-quantum) sub-exponentially secure indistinguishability obfuscation, injective one-way functions, the quantum hardness of learning with errors, and the two versions of a new conjecture called the simultaneous inner product conjecture. The security of the second construction is based on the existence of unclonable-indistinguishable bit encryption, injective one-way functions, and quantum-state indistinguishability obfuscation.