Could the no-cloning property of quantum information be used to protect ciphertexts against copying? In 2002, Gottesman answered this question in the positive, proposing a quantum encryption scheme for classical messages, with a decryption process that detects any attempt to copy the ciphertext. Clearly, classical information alone does not allow such a functionality, since it is always possible to perfectly copy a classical ciphertext while avoiding detection. However, Gottesman left open the question of restricting the knowledge that two recipients could simultaneously have on a plaintext, after an attack on a single ciphertext. Here, we address this open question by showing that Wiesner's conjugate coding can be used to achieve this type of uncloneable encryption for classical messages. Our approach is a prepare-and-measure scheme and the analysis is done in the quantum random oracle model, using techniques from the analysis of monogamy-of-entanglement games.
Reference: Anne Broadbent and Sébastien Lord. Uncloneable Quantum Encryption via Random Oracles. arXiv:1903.00130.