Eur. Phys. J. D 18, 219-228 (2002)
https://doi.org/10.1140/epjd/e20020026

Statistical confidentiality tests for a quantum transmission using continuous variables

INFM, Dipartimento di Scienze CC FF MM, Universita degli Studi dell'Insubria, Via Valleggio 11, 22100 COMO, Italy

Corresponding authors: ^a navez@ptt.mi.infn.it navez@ulam.fis.unico.it

Received: 12 July 2001
Revised: 11 November 2001
Published online: 15 February 2002

Abstract

We describe a cryptographic protocol consisting of two entangled beams of squeezed light which makes use of statistical tests to deduce the secret key bit. The sender (Alice) encrypts a secret key by modulating the phase of the beam sent in public by the receiver (Bob) who keeps the other beam private. The knowledge of the degree of non classical correlation between the beam quadrature components measured in private and in public allows only Bob to decrypt the secret key. With a view towards absolute security, we formally prove that any external intervention from an eavesdropper (Eve) during the communication process introduces necessarily some modification susceptible to be detected. Statistical confidentiality tests are proposed to detect the presence of Eve.