Everlasting Secrecy by Exploiting Non-Idealities of the Eavesdropper's Receiver

TL;DR

This paper introduces a novel physical-layer security method exploiting non-linearities in the eavesdropper's receiver, combined with cryptographic keys, to achieve everlasting secrecy even when the eavesdropper has superior channel conditions.

Contribution

It presents a new approach that leverages non-linear operations and cryptographic keys to ensure information-theoretic secrecy without channel advantage.

Findings

Positive secrecy rates achievable even with better eavesdropper conditions

Non-linear operations can be exploited to prevent eavesdropper from extracting information

Method remains effective despite eavesdropper having immediate access to cryptographic keys

Abstract

Secure communication over a memoryless wiretap channel in the presence of a passive eavesdropper is considered. Traditional information-theoretic security methods require an advantage for the main channel over the eavesdropper channel to achieve a positive secrecy rate, which in general cannot be guaranteed in wireless systems. Here, we exploit the non-linear conversion operation in the eavesdropper's receiver to obtain the desired advantage - even when the eavesdropper has perfect access to the transmitted signal at the input to their receiver. The basic idea is to employ an ephemeral cryptographic key to force the eavesdropper to conduct two operations, at least one of which is non-linear, in a different order than the desired recipient. Since non-linear operations are not necessarily commutative, the desired advantage can be obtained and information-theoretic secrecy achieved even if the eavesdropper is given the cryptographic key immediately upon transmission completion. In essence, the lack of knowledge of the key during the short transmission time inhibits the recording of the signal in such a way that the secret information can never be extracted from it. The achievable secrecy rates for different countermeasures that the eavesdropper might employ are evaluated. It is shown that even in the case of an eavesdropper with uniformly better conditions (channel and receiver quality) than the intended recipient, a positive secure rate can be achieved.