An Authenticity Verification Scheme Based on Hidden Messages for Current Civilian GPS Signals

Aiming at the authentication of civilian signals broadcasted by currently orbiting GPS satellites, this paper proposes a new technique, which carries GPS authentication information by the messages hidden in the navigation message and, without affecting the position fixing of GPS receivers in use all over the world, appends the capability of authenticity verification to current civilian GPS signals. Hidden messages are transmitted to receivers through reserved bits in the Nav navigation message or newly-added CNav message types. The civilian GPS signal authentication information is obtained by using the Hash function to convert the navigation message and (or) C/A code into Hash code and then digitally signing the Hash code with public key encryption algorithm. This paper also analyzes the feasibility, covertness and channel capacity of the hidden message transmission, puts forward several design samples of navigation message formats and explores the issues of the use patterns of hidden messages and the number of public/private key pairs.