Abstract
In this work, we consider the pros and cons of using various layers of keyless coding to achieve secure and reliable communication over the Gaussian wiretap channel. We define a new approach to information theoretic security, called practical secrecy and the secrecy benefit, to be used over real-world channels and finite blocklength instantiations of coding layers, and use this new approach to show the fundamental reliability and security implications of several coding mechanisms that have traditionally been used for physical-layer security. We perform a systematic/structured analysis of the effect of error-control coding, scrambling, interleaving, and coset coding, as coding layers of a secrecy system. Using this new approach, scrambling and interleaving are shown to be of no effect in increasing information theoretic security, even when measuring the effect at the output of the eavesdropper’s decoder. Error control coding is shown to present a trade-off between secrecy and reliability that is dictated by the chosen code and the signal-to-noise ratios at the legitimate and eavesdropping receivers. Finally, the benefits of secrecy coding are highlighted, and it is shown how one can shape the secrecy benefit according to system specifications using combinations of different layers of coding to achieve both reliable and secure throughput.
Highlights
Physical-layer security [1] is currently undergoing a resurgence of interest and activity, regarding progressing towards real-world application of information theoretic security principles [2,3,4]
Since the metric is a practical one, its application to finite blocklength codes with known explicit constructions is highlighted. Along with this new security metric, we present the idea of a code’s secrecy benefit, which, over the Gaussian wiretap channel, shows the increase in confusion at the eavesdropper for the coded scenario over the uncoded scenario as a function of signal-to-noise ratio
We show that keyless layers of scrambling and interleaving provide no secrecy benefit over the uncoded case, error-control coding layers can be used to increase security or reliability depending on the signal-to-noise ratios at the legitimate and eavesdropping receivers, and the secrecy benefit of coset-based secrecy codes can be shaped using error-control coding
Summary
Physical-layer security [1] is currently undergoing a resurgence of interest and activity, regarding progressing towards real-world application of information theoretic security principles [2,3,4]. The contributions of this paper include a systematic and structured analysis of error-control coding, interleaving, scrambling, and coset-based secrecy coding, as layers in a physical-layer security coding system We chose these layers so as to represent fundamentally different approaches to coding for secrecy over the Gaussian wiretap channel, and leave additional layers of coding, such as other constructions of wiretap codes [8,9], for future work. We assign capital letters to random variables and matrices, lowercase letters to realizations of random variables, calligraphic letters to ranges of random variables, superscripts to indicate the size of vectors and matrices, and subscripts to index the elements of vectors and matrices
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