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Information-theoretic Physical Layer Security for Satellite Channels

Angeles Vazquez-Castro, Masahito Hayashi

TL;DR

The paper argues that information-theoretic physical-layer security via wiretap coding can enable keyless secrecy for satellite channels. It develops a general wiretap code construction using coset encoding and randomized universal hash functions, and maps satellite links to the wiretap model with realistic large- and short-scale fading and geometry effects. It derives both infinite-length secrecy capacity results for Gaussian satellite channels and finite-length strong-secrecy bounds, illustrating operational points for DVB-S2X and the Euclid mission. The work demonstrates the potential for unconditional security on satellite links and provides a design framework for integrating wiretap coding with other security protocols in a layered security architecture.

Abstract

Shannon introduced the classic model of a cryptosystem in 1949, where Eve has access to an identical copy of the cyphertext that Alice sends to Bob. Shannon defined perfect secrecy to be the case when the mutual information between the plaintext and the cyphertext is zero. Perfect secrecy is motivated by error-free transmission and requires that Bob and Alice share a secret key. Wyner in 1975 and later I.~Csiszár and J.~Körner in 1978 modified the Shannon model assuming that the channels are noisy and proved that secrecy can be achieved without sharing a secret key. This model is called wiretap channel model and secrecy capacity is known when Eve's channel is noisier than Bob's channel. In this paper we review the concept of wiretap coding from the satellite channel viewpoint. We also review subsequently introduced stronger secrecy levels which can be numerically quantified and are keyless unconditionally secure under certain assumptions. We introduce the general construction of wiretap coding and analyse its applicability for a typical satellite channel. From our analysis we discuss the potential of keyless information theoretic physical layer security for satellite channels based on wiretap coding. We also identify system design implications for enabling simultaneous operation with additional information theoretic security protocols.

Information-theoretic Physical Layer Security for Satellite Channels

TL;DR

The paper argues that information-theoretic physical-layer security via wiretap coding can enable keyless secrecy for satellite channels. It develops a general wiretap code construction using coset encoding and randomized universal hash functions, and maps satellite links to the wiretap model with realistic large- and short-scale fading and geometry effects. It derives both infinite-length secrecy capacity results for Gaussian satellite channels and finite-length strong-secrecy bounds, illustrating operational points for DVB-S2X and the Euclid mission. The work demonstrates the potential for unconditional security on satellite links and provides a design framework for integrating wiretap coding with other security protocols in a layered security architecture.

Abstract

Shannon introduced the classic model of a cryptosystem in 1949, where Eve has access to an identical copy of the cyphertext that Alice sends to Bob. Shannon defined perfect secrecy to be the case when the mutual information between the plaintext and the cyphertext is zero. Perfect secrecy is motivated by error-free transmission and requires that Bob and Alice share a secret key. Wyner in 1975 and later I.~Csiszár and J.~Körner in 1978 modified the Shannon model assuming that the channels are noisy and proved that secrecy can be achieved without sharing a secret key. This model is called wiretap channel model and secrecy capacity is known when Eve's channel is noisier than Bob's channel. In this paper we review the concept of wiretap coding from the satellite channel viewpoint. We also review subsequently introduced stronger secrecy levels which can be numerically quantified and are keyless unconditionally secure under certain assumptions. We introduce the general construction of wiretap coding and analyse its applicability for a typical satellite channel. From our analysis we discuss the potential of keyless information theoretic physical layer security for satellite channels based on wiretap coding. We also identify system design implications for enabling simultaneous operation with additional information theoretic security protocols.

Paper Structure

This paper contains 16 sections, 49 equations, 11 figures.

Table of Contents

  1. Introduction
  2. The wiretap channel and security criteria
  3. The wiretap channel
  4. Security metrics and wiretap coding design goals
  5. Security analysis
  6. General wiretap code construction
  7. Randomized hash function
  8. Satellite wiretap channel model
  9. Transmitted signal model
  10. Large-scale model
  11. Medium/short-scale model
  12. Comparison with spread spectrum signal model
  13. Satellite Gaussian channel model
  14. Secrecy analysis: infinite-length regime
  15. Security analysis: finite-length regime
  16. ...and 1 more sections

Figures (11)

  • Figure 1: Illustration of Eve's closest angular distance to Alice (as a function of relative distances) so Eve's signal amplitude is $\gamma_g<1$.
  • Figure 2: Illustration of the influence of wiretap system parameters on Eve's amplitude signal degradation for different values of system parameters.
  • Figure 3: Illustration of the influence of wiretap channel propagation on Eve's amplitude signal degradation for different propagation laws.
  • Figure 4: Secrecy capacity showing the effect of Eve's noise.
  • Figure 5: Comparison of BI-AWGN Bob's and Eve's capacities with known Gaussian and BSC capacities. Eve's capacity is shown for the case $\gamma_g=0.5$
  • ...and 6 more figures