Shannon proved in 1949 that information-theoretic-secure encryption is possible if the encryption key is used only once, is random, and is at least as long as the message itself. Notwithstanding, when information is encoded in a quantum system, the phenomenon of quantum data locking allows one to encrypt a message with a shorter key and still provide information-theoretic security. We present one of the first feasible experimental demonstrations of quantum data locking for direct communication and propose a scheme for a quantum enigma machine that encrypts 6 bits per photon (containing messages, new encryption keys, and forward error correction bits) with less than 6 bits per photon of encryption key while remaining information-theoretically secure.
Bibliographical noteFunding Information:
Contribution of NIST, an agency of the U.S. government, not subject to copyright. The authors thank J. Schneeloch and S. Knarr for editing and useful input. This work was sponsored by DARPA-DSO Quiness Grant No. W31P4Q-12-1-0015 and AFOSR Grant No. FA9550-13-1-0019.
© 2016 American Physical Society.