Effective privacy amplification for secure classical communications

¹ Department of Computer Science, University of Bonn - Bonn, Germany, EU
² Fraunhofer IAIS, Schloss Birlinghoven - D-53754 Sankt Augustin, Germany, EU
³ Department of Electrical and Computer Engineering, Texas A&M University - College Station, TX 77843-3128, USA
⁴ School of Electrical Engineering, Tel-Aviv University - Ramat-Aviv, Israel
⁵ Center for Nanoscience and Nanotechnology, Tel-Aviv University - Ramat-Aviv, Israel

^a tamas.horvath@iais.fraunhofer.de
^b laszlo.kish@mail.ece.tamu.edu
^c kobys@eng.tau.ac.il

Received: 24 January 2011
Accepted: 15 March 2011

Abstract

We study the practical effectiveness of privacy amplification for classical key distribution schemes. We find that in contrast to quantum key distribution schemes, the high fidelity of the raw key generated in classical systems allow the users to always sift a secure shorter key if they have an upper bound on the eavesdropper probability to correctly guess the exchanged key bits. The number of privacy amplification iterations needed to achieve information leak of 10⁻⁸ in existing classical communicators is 2 or 3 resulting in a corresponding slowdown 4 to 8. We analyze the inherent tradeoff between the number of iterations and the security of the raw key. This property which is unique to classical key distribution systems render them highly useful for practical, especially for noisy channels where sufficiently low quantum bit error ratios are difficult to achieve.