Two-way and one-way quantum cryptography protocols

Ben Rothke

Ahmed Mahmoud Sofy, Mohamed Ahmed Shalaby, Hisham Dahshan +1 more

The present cryptography systems security depends on the hardness of factorizing an integer number with a large number of digits to its prime integer factors. In 1994, Peter Shor proposed a quantum procedure (Shor's algorithm) that easily factorizes large integer numbers to its prime factors compared with other algorithms. Consequently, present cryptography systems became endangered and once quantum computers exist, conventional cryptography systems could breakdown. On the other hand, quantum cryptography security is based on the well-known quantum mechanics uncertainty principle, and so the quantum cryptography enhances the cryptography field with a mechanism for eavesdropper detecting. Here, a hardware implementation was proposed for two types of key distribution protocols based on quantum computing, the one-way quantum key distribution protocol (BB84 protocol), and the two-way quantum key distribution protocol.

Ben Rothke

Christian Weedbrook, Carlo Ottaviani, Stefano Pirandola

We study the security of two-way quantum cryptography at different wavelengths of the electromagnetic spectrum, from the optical down to the microwave range. In particular, we consider a two-way quantum communication protocol where Gaussian-modulated thermal states are subject to random Gaussian displacements and finally homodyned. We show how its security threshold (in reverse reconciliation) is extremely robust with respect to the preparation noise and able to outperform the security thresholds of one-way protocols at any wavelength. As a result, improved security distances are now accessible for implementing quantum key distribution in the very challenging regime of infrared frequencies.

Bassem Abd-El-Atty, Salvador Elías Venegas-Andraca, Ahmed A. Abd El‐Latif

Masato Koashi, N. Imoto

Summary form only given.One of the simplest protocols of quantum cryptography proposed so far is the one based on two nonorthogonal states. In this protocol, the receiver cannot determine every bit because there is no way to distinguish nonorthogonal states completely. Another simple protocol uses two orthogonal states, and the receiver can always discriminate between the two states that represent the bit values 0 and 1. In this protocol, however, the sender must mix the third states (vacuum states) in the bit stream to prevent eavesdropping. Thus the following question arises: do more simple protocols exist in which the sender switches between only two states and the receiver can obtain every bit value? Here we show that such a protocol does exist.