Effective Privacy Amplification for Secure Classical Communications

TL;DR

This paper demonstrates that classical key distribution systems can reliably produce secure shorter keys through privacy amplification, especially in noisy channels, with minimal iterations needed for high security.

Contribution

It shows that classical systems can effectively implement privacy amplification with few iterations, contrasting quantum schemes, and analyzes the tradeoff between iterations and security.

Findings

2-3 iterations suffice for high security (10^-8 leak)

Classical systems outperform quantum in noisy channels

Minimal slowdown (4-8 times) for secure key generation

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.