The Enigma Encryption Machine Turns Quantum Data Locking Theory Into Reality

In the paper entitled “Quantum enigma machine: Experimentally demonstrating quantum data locking,” published by the Physical Review A, University of Rochester researchers led by Daniel Lum showed that “the phenomenon of quantum data locking allows one to encrypt a message with a shorter key and still provide information-theoretic security.”

Let’s begin with some background.

In 1949, Claude Shannon – considered as the “father of information theory” – proved that secure encryption is possible, provided that these three conditions are present:
1. Encryption key is used only once;
2. Encryption key is random; and
3. Encryption key is at least as long as the message itself.

Researchers at the University of Rochester demonstrated for the first time that secure encryption is possible even with a shorter key.

The University of Rochester researchers wrote, “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.”

For this experiment, Lau and associates used an encryption machine called “Quantum Enigma Machine.”

The name “Enigma” came from the Enigma machine, an encryption machine developed by the Germans during World War II. Ultimately, British and Polish mathematicians broke the Enigma code.

Quantum data locking?

The theory of quantum data locking has been around for nearly ten years. Within this span of time, only a few academic papers were devoted to the cryptography application.

Quantum data locking is an encryption method put forward by Seth Lloyd, professor of quantum information at Massachusetts Institute of Technology. This encryption method uses tiny particles associated with light called photons to carry a message.

For a long time, quantum data locking remained a theory. Lum and his associates put this quantum data locking theory into practice by developing the Quantum Enigma Machine.

“It’s highly unlikely that our free-space implementation will be useful through atmospheric conditions,” Lum told

Lum added:

Instead, we have identified the use of optic fiber as a more practical route for data locking, a path Pan’s (Jian-Wei Pan) group actually started with. Regardless, the field is still in its infancy with a great deal more research needed.

On 12 August 2016, the same day that Lum and associates’ paper was published, the Physical Review A also published the paper entitled “Experimental quantum data locking” by Chinese physicists led by Pan.

Similarly, Pan and associates found that it is possible to lock a large volume of data with the use of short encryption key.

“Quantum data locking presents a resource-efficient alternative to one-time pad encryption which requires a key no shorter than the message,” Pan and associates said.

Featured image from iStock/&#169 Nick Schlax.