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

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

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.

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?

Overview of secure channels

Cryptographic spread spectrum

Wiretap channel approaches

RF fingerprinting

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!

Towards a white paper

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

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

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

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!