Paper 2020/877

Unclonable Decryption Keys

Marios Georgiou and Mark Zhandry

Abstract

We initiate the study of encryption schemes where the decryption keys are unclonable quantum objects, which we call single decryptor encryption. We give a number of initial results in this area: -We formalize the notion of single decryptor encryption. -We show that secret-key single decryptor encryption is possible unconditionally, in the setting where a limited number of ciphertexts are given. However, given an encryption oracle, we show that unconditional security is impossible. -We show how to use a very recent notion of one-shot signatures, together with sufficiently powerful witness encryption, to achieve public key single decryptor encryption. -We demonstrate several extensions of our scheme, achieving a number of interesting properties that are not possible classically.

Note: Corrected key naming for definitions of single decryptor encryption with dishonestly generated keys.