Secret key expansion from covert communication

TL;DR

This paper demonstrates how covert communication can be utilized for secret key expansion, allowing more secret key material to be generated than consumed under certain low-noise conditions, enhancing secure communication.

Contribution

It introduces a novel protocol for secret key expansion using covert communication and establishes conditions for its security and effectiveness.

Findings

Secret key expansion is possible with covert communication under low-noise conditions.

Any message transmitted covertly remains secret and unknown to adversaries.

The protocol achieves key expansion with less key consumption than the amount transmitted.

Abstract

Covert communication allows us to transmit messages in such a way that it is not possible to detect that the communication is occurring. This provides protection in situations where knowledge that people are talking to each other may be incriminating to them. In this work, we study how covert communication can be used for a different purpose: secret key expansion. First, we show that any message transmitted in a secure covert protocol is also secret and therefore unknown to an adversary. We then propose a protocol that uses covert communication where the amount of key consumed in the protocol is smaller than the transmitted key, thus leading to secure secret key expansion. We derive precise conditions showing that secret key expansion from covert communication is possible when there are sufficiently low levels of noise for a given security level. We conclude by examining how secret key expansion from covert communication can be performed in a computational security model.