Alice, Bob and Eve - Quantum Cryptography

Jack Dikian

June 2011

Quantum cryptography is the use of quantum systems to perform cryptographic tasks. A key application of quantum cryptography is quantum key distribution (QKD). QKD describes the process of using quantum communication to establish a shared key between two parties Alice and Bob without a third party Eve learning anything about that key, even if Eve can eavesdrop on all communication between Alice and Bob.

This is due to the process of measuring a quantum system in general disturbs the system. A third party trying to eavesdrop on the key must in some way measure it, thus introducing detectable anomalies.

In contrast traditional cryptography often relies on mathematical theorems that may be vulnerable to attacks by individuals armed with increasingly powerful supercomputers.

But, even though QKD is theoretically secure researchers have been aware that loopholes may arise when QKD is used in real world applications.

Now, a team of researchers at the Centre for Quantum Technologies at the National University of Singapore, the Norwegian University of Science and Technology and the University Graduate Center in Norway have created a perfect eavesdropper for QKD allowing researchers to obtain an entire shared secret key without alerting either of the legitimate parties that there had been a security breach.