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A quantum enigma machine: Experimentally demonstrating quantum data locking



Daniel Lum, Michael S. Allman, Thomas Gerrits, Cosmo Lupo, Seth Lloyd, Varun Verma, Sae Woo Nam, John Howell


During the first half of the 20th century, enigma machines (i.e., pseudorandom polyalphabetic ciphers) of increasing sophistication gave better resistance against brute-force codebreaking attacks. However, the ultimate form of cryptographic security is information theoretic security which makes no assumptions of an adversary's capabilities. Shannon proved in 1949 that information-theoretic security is possible if the encryption key is used only once, is random, and is at least as long as the message itself. This introduced the difficult task of distributing a truly secret key between parties. The field of Quantum Key Distribution (QKD) solves this problem utilizing fundamental quantum uncertainties. Unfortunately, QKD is currently confined to slow bit rates, and it cannot be employed for direct message transmission. Quantum Data Locking (QDL) employs quantum information theory to do what Shannon proved impossible according to classical information theory. QDL serves as a quantum enigma machine, providing information-theoretic security while encrypting a message with a key that is exponentially shorter than the message itself. We propose and test an experimental realization of a quantum enigma machine in which we securely transfer both messages and secret keys encoded on single photons. Hence, once an initial key has been securely established according to QKD, we can indefinitely transmit messages and new secret keys without delay.
A 94


quantum key distribution, superconducting nanowire detectors, single photon detector arrays, quantum data locking


Lum, D. , Allman, M. , Gerrits, T. , Lupo, C. , Lloyd, S. , Verma, V. , Nam, S. and Howell, J. (2016), A quantum enigma machine: Experimentally demonstrating quantum data locking, Nature, [online], A.94 022315, (Accessed March 4, 2024)
Created August 11, 2016, Updated October 12, 2021