1. Physical Layer Security
05/08/2017
IGNACIO AGUILAR SANCHEZ, ESA
CHARLES SHEEHE, NASA

2. Outline Introduction Overview of secure channels
COMSEC
TRANSEC
Non-crypto approaches
Main physical layer security concepts
Cryptographic spread spectrum
Wiretap channel
RF fingerprinting
Prospects for CCSDS
White, then Green Book
Blue Books?
Preliminary conclusions and follow-on
Towards a White paper

3. Introduction (1/2) Purpose Scope
Initiate CCSDS discussion and possibly future work on physical layer security concepts, techniques and related technologies as a future component of space mission security engineering portfolio.
Scope
Today a short presentation introducing the subject and its most important elements.

4. Introduction (2/2) Motivation
CCSDS has already tackled link and network layers on its security engineering effort (e.g. SDLS).
Certain threats can only be mitigated at physical layer (e.g. denial of service by deliberate interference, signal interception).
But more interestingly physical layer has been rediscovered to secure communication channels with security services traditionally assigned to upper (data) layers (e.g. authentication, confidentiality) and with a promise of information-theoretic strong security (vs. computationally-strong) without a key management burden. Really?

5. Overview of secure channels

6. Cryptographic spread spectrum

7. Wiretap channel approaches

8. RF fingerprinting

9. Prospects for CCSDS White Book followed by Green Book
The subject is broad and complex, touching disciplines covered by several CCSDS WGs…but could provide useful complements and/or novel solutions to engineer security on space missions
Research hot topic for wireless communications security with strong interest by both civilian and governmental communities
Deeper understanding of the subject as well as relevant research results, expected benefits, future mission requirements, etc. before deciding on any potential standard
Joint SEC, RFM and S&CC task?
Cautious but thorough approach!

10. Towards a white paper

11. Physical Layer Security White Paper Outline
INTRODUCTION
INTRODUCTORY SUBSECTIONS
REFERENCES
OVERVIEW OF SECURE CHANNELS
SECURE CHANNELS
COMMUNICATIONS SECURITY (COMSEC)
TRANSMISSION SECURITY (TRANSEC)
NON-CRYPTOGRAHIC APPROACHES
MAIN PHYSICAL LAYER SECURITY CONCEPTS
CRYPTOGRAPHIC SPREAD SPECTRUM
SPREAD SPECTRUM
PSEUDORANDOM SEQUENCES
ISSUES
WIRETAP CHANNEL APPROACHES
THE WIRETAP CHANNEL
INJECTION OF ARTIFICIAL NOISE
KEY DERIVATION
CODING FOR SECRECY
CHANNEL UNIQUENESS
TRANSMITTER UNIQUENESS - RF FINGERPRINTING
THE RADIO IN THE FINGERPRINT
THE REMOVAL OF INPUT FROM THE OUTPUT
COMPARISONS
CONCLUSION
PROSPECTS FOR CCSDS
EXPECTED BENEFITS
REQUIREMENTS FOR PROSPECTIVE MISSIONS
RELATIONSHIP WITH EXISTING STANDARDS
IDENTIFIED DEFICIENCIES, FLAWS, AND LIMITATIONS IN EXISTING STANDARDS
GREEN BOOK ON PHYSICAL LAYER SECURITY
BLUE BOOKS
OVERVIEW
OPTICAL LINK ENCRYPTION AND KEY DERIVATION
CONCLUSION AND RECOMMENDATIONS

12. Physical Layer Security paper process
Develop Physical Layer paper outline
Public references for each section
Expand each section
Review of Physical Security Layer paper by Security Working Group
Refine paper structure and content
RF Modulation Working Group buy in and provide feed back on Physical Security Layer paper
Refine paper
Publish Physical Layer Security paper

13. Physical Layer Security questions / notes
Introduce the schematic of RF fingerprinting identification process (transmitter+wireless channel+receiver).

14. Some good readings
C. E. Shannon, “Communication theory of secrecy systems,” Bell System Technical Journal, vol. 28, no. 4, pp. 656–715, April 1949.
A. D. Wyner, “The wire-tap channel,” Bell System Technical Journal, vol. 54, no. 8, pp. 1355–1367, October 1975.
“Physical-Layer Security From Information Theory to Security Engineering”, M. Bloch and J. Barros, Cambridge University Press, 2011.
“Algebraic Shift Register Sequences”, M. Goresky and A. Klapper, Cambridge University Press, 2012.
“Information Theoretic Security”, Yingbian Liang, H. Vincent Poor and Shlomo Shamai (Shitz), Foundations and Trends in Communications and Information Theory, Vol. 5 Issue 4-5, 2008.
…..
To be completed!