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Practical Cryptographic Civil GPSSignal Authentication
Kyle Wesson, Mark Rothlisberger, and Todd Humphreys
Presentation at ION 2011| September 23, 2011
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What does it take to authenticate a GNSS Signal?
Code Origin AuthenticationCode Timing Authentication
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Specially-Weighted Correlations
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Operational Definition of GNSS Signal Authentication GNSS signal is declared authentic if:
1. Logical output S has remained low2. Logical output H1 has remained low, and 3. Output PD has remained above an acceptable threshold
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1. Effective: they make it difficult for a spoofer to carry off a successful spoofing attack
2. Practical: they are likely to be implemented and adopted by the GPS community
What qualities should cryptographic civil GPS signal authentication have?
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A strategy that meets these requirements:
Navigation Message Authentication (NMA):
Forms by making the navigation message periodically unpredictable
Applies public-key cryptographic digital signature and verification techniques
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CNAV Message
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Signing the CNAV Message
• Delivers ECDSA signature every five minutes per channel• Delivers 476 unpredictable navigation message bits• Offset scheme could lower time-between-authentications
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Hypothesis Testing on Security Code
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Probability of Detection under Challenging Scenario
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http://radionavlab.ae.utexas.edu/publications