SNAPSHOT AND AUTHENTICATION TECHNIQUES FOR SATELLITE NAVIGATION by Ignacio Fernández Hernández Dissertation submitted to the Faculty of Engineering and Science at Aalborg University in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Electrical Engineering. I SNAPSHOT AND AUTHENTICATION TECHNIQUES FOR SATELLITE NAVIGATION Thesis submitted: May 7th, 2015 PhD supervisors: Prof. Kai Borre, Aalborg University Prof. Torben Larsen, Aalborg University PhD committee: Prof. Per K. Enge, Stanford University Dr. Frank van Diggelen, Broadcom Corporation Prof. Søren Holdt Jensen, Aalborg University PhD Series: Faculty of Engineering and Science, Aalborg University II ENGLISH SUMMARY Since GPS was declared fully operational in 1995, satellite navigation technologies have evolved in many ways. Two of them are the drivers for this doctoral thesis: satellite navigation authentication and snapshot positioning techniques. The first research area of this thesis is GNSS authentication. In spite of the high importance of GNSS in our society and economy, its civil signals are easy to counterfeit. This thesis proposes novel techniques and concepts, such as satellite cross-authentication, single key chains for all satellites, and offsetting schemes, to improve the performance of navigation message authentication. It presents and analyses a solution requiring less than two hundred bits for authenticating four satellites, providing high availability and robustness. The second research area of this thesis is snapshot positioning. Snapshot techniques are based on computing a position using only a set of digital signal samples captured over some milliseconds. Existing techniques require a rough knowledge of the position and/or time at which the snapshot was captured. This thesis proposes and characterizes a novel method to instantaneously compute a snapshot position without any initial information. The proposed method does not cause any accuracy or availability degradation compared to other state-of- the-art snapshot methods. In relation to the previous area, this thesis also deals with the generalization of the snapshot positioning concept to non-GNSS satellites. By using more powerful signals from non-GNSS satellites, indoors localization and resilience can be improved. This thesis proposes a method based on a ground network that processes non-GNSS satellite signal snapshots and is able to compute from them the instantaneous position and other reference parameters of those satellites. Thus, a receiver can get a fix by receiving its own snapshot and the associated instant satellite parameters from the ground network. Experimentation shows that, depending on the satellite-ground geometry and signal characteristics, metre-level accuracies are possible with this method. This thesis also presents some research initial on the combination of authentication and snapshot positioning. Snapshot authentication methods based on a trusted clock and geometrical constraints are proposed to authenticate unpredictable signals through snapshot techniques. III SNAPSHOT AND AUTHENTICATION TECHNIQUES FOR SATELLITE NAVIGATION DANSK RESUME GPS blev erklæret fuldt operationelt i 1995. Siden da har teknologien bag satellit navigation udviklet sig på mange måder. To af dem er drivkraften bag denne Ph D afhandling: troværdighed (på engelsk: authentication) af satellitbaseret navigation og metoder for snap- shot positionering. Det første forskningsområde i denne afhandling vedrører troværdigheden af GNSS. På trods af den store betydning af GNSS i vores samfund og økonomi er det let at forfalske de civile signaler. Denne afhandling foreslår nye teknikker og begreber -- som kryds-troværdighed mellem satellitter, signatur for alle satellitter og forskydningstabeller -- for at sikre troværdigheden af navigationsdata. Den fremlægger og analyserer en løsning, der kræver mindre end to hundrede bits for at gøre fire satellitter troværdige, tilvejebringe høj tilgængelighed og robusthed. Afhandlingens andet forskningsområde vedrører snap-shot positionering. Snap-shot metoder beregner en position udelukkende på grundlag af et sæt signaler hver af en varighed på få millisekunder. Eksisterende metoder kræver kendskab til position og/eller det tidspunkt, hvor snap-shottet blev indsamlet. Denne afhandling foreslår og karakteriserer en hidtil uset metode til øjeblikkeligt at beregne en snap-shot position uden nogen forudgående information. Den foreslåede metode indebærer ikke forringet nøjagtighed eller tilgængelighed sammenlignet med de mest avancerede snap-shot metoder. I tilknytning til det foregående emne indeholder denne afhandling også en generalisering af snap-shot positionering, så den omfatter ikke-GNSS satellitter. Ved at anvende kraftigere signaler fra ikke-GNSS satellitter kan man forbedre indendørs lokalisering og den tilknyttede robusthed. Denne afhandling foreslår en metode -- baseret på et jordbaseret net -- som beregner snap-shots fra ikke-GNSS satellitter og er i stand til også at beregne en øjeblikkelig position og andre reference parametre for disse satellitter. Herved kan en bruger beregne en position ved at modtage sit eget snap-shot og de tilknyttede øjeblikkelige satellit parametre fra det jordbaserede net. Eksperimenter viser, at afhængig af satellit-jord geometrien og signal egenskaberne er det muligt at opnå meter nøjagtighed med denne metode. IV Et fjerde forskningsområde, der sættes i gang i denne afhandling, er kombinationen af troværdighed og snap-shot positionering. Der foreslås en snap-shot metode, der baserer sig på en pålidelig ekstern ur-reference, hvorved uforudsigelige signaler kan gøres troværdige gennem snap-shot teknikker. V ACKNOWLEDGEMENTS First, I would like to thank my supervisors Prof. Kai Borre and Prof. Torben Larsen, from AAU, for facilitating so much the process of preparing my PhD candidature. Prof. Borre has given me very valuable strategic advice and a lot of technical and moral support over these years, and Prof. Larsen has helped me a lot on the home strait of the thesis. Both have given me their trust and a lot of flexibility in the orientation the research activities, which I highly appreciate. I would like to give specially thanks Prof. Gonzalo Seco-Granados, for his generosity and patience in sharing some of his vast knowledge and perspicacity with me. His help extends throughout all the research in this thesis, including both snapshot and authentication areas. He has provided many useful references and suggestions, especially, but not only, on signal-related aspects. The work on authentication relates to my job duties and my job colleagues have partly supported it. I have been luckily surrounded by very good engineers “helping the cause” of authenticating Galileo in a selfless, constructive and collaborative way, reviewing and discussing material and making insightful comments. I would like to thank Prof. Vincent Rijmen for providing many references and recommendations used in this thesis concerning the cryptographic parts and for being available to share his insight during our long discussions. I also appreciated Dr. Paul Walker's critical review and useful suggestions. The review and sharp comments from Andrew Kerns and Prof. Todd Humphreys have been also very valuable. Javier Simón, Guillermo Tobías, David Calle, Enrique Carbonell and Irma Rodríguez, with the support of Oscar Pozzobon, Laurens Bogaardt and Dominic Hayes, have also significantly contributed to improving the quality of our publications on the subject. In addition, I would like to thank my colleagues at EC/GSA Fiammetta Diani, Jean Marechal and Eric Châtre for their determination and support. On the snapshot research area, I would like to thank Oriol Badia for giving me access to some of the snapshot data captures and Matlab code from his Master's Thesis at AAU. I would also like to thank Michele Bavaro for kindly lending me one of his SDRs, and Darius Plaušinaitis. 6 Dr. Frank van Diggelen's A-GPS book, Prof. Enge's GPS book, and Prof. Borre's GNSS SDR book are the three main references that have allowed me to “triangulate” and find my way through this thesis, with the regular assistance channel of Prof. Seco. I am highly privileged in having Dr. van Diggelen and Prof. Enge, together with Prof. S. J. Jensen, in my PhD assessment committee. I would like to thank them for their availability and inspirational contributions, without which this thesis would not probably have been even started. Finally, but most importantly, I would like to thank Paloma, my wife, for her continuous support during this journey. The information and views set out in this dissertation are those of the author and do not necessarily reflect the official opinion of the European Union. 7 SNAPSHOT AND AUTHENTICATION TECHNIQUES FOR SATELLITE NAVIGATION TABLE OF CONTENTS Chapter 1. Introduction ..................................................................................................... 17 1.1. Scientific Challenges and Main Contributions....................................................... 17 1.2. Thesis Outline ........................................................................................................ 20 Chapter 2. General Technical Background ....................................................................... 21 2.1. A Brief History of Navigation ................................................................................ 21 2.2. Radionavigation Methods .....................................................................................