Abstract:

Claude 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
an exponentially shorter key and still provide information-theoretic security. We present the first feasible experimental
demonstration 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.