The objectives of this study are :- Identify advantages and drawbacks of different key management concepts and techniques including the state of the art , those proposed for the current GNSS system. Opening the research to schemes which are used also in other context e.g. 3GPP, SATCOM, etc.- Select a number of candidate schemes for evaluation- Define figures of merit (metrics) for evaluation- Develop simulation tools including a scenario-generation simulator and user receiver emulator using a semi-analytic approach to evaluate the performance of the candidate schemes

In the long term evolution of GNSS, it is expected that new signals and innovative signal designs will be conceived to support the next-generation of GNSS applications. These future GNSS signals will require innovative protection mechanisms to enable the business models of value-added services from multiple service providers, ensuring the protection of service revenues. Controlling access to GNSS signals and value-added data would typically be achieved through the use of two general techniques:- Spreading code encryption: where access to the signal is restricted to authorized users with the correct code generation parameters (keys). These users are able to generate the replica code in order to de-spread the signal. The security principle is based on the notion that the signal arrives below thermal noise, and therefore without the correct replica code, acquisition of the signal is intractable.- Navigation data encryption: where portions of the navigation message containing value-added service data can be restricted to authorized users using data encryption.Signal access control mechanisms based on the spreading code encryption paradigm have one significant drawback: all authorized users have common code generation parameters. In other words, the cryptonet for access to a given GNSS signal would be the entire set of authorized users that can generate the correct replica code for that signal. A major challenge in developing suitable key management schemes are the complexities associated with supporting the needs of a wide range of applications, with vastly different mission requirements, further complicated by a bandwidth, constrained environment and a range of different risk profiles for security of the code generation parameters. For this reason, tools to objectively evaluate their performance are essential to the design of robust and resilient protection mechanisms for future GNSS signals.The aim of this activity is broaden the pool of innovative key management concepts and techniques scheme to be used for future systems (benefiting also from ideas coming from non GNSS context e.g. 3GPP, SATCOM), to support their evaluation through the development of simulation tools that allow all aspects of key management including key establishment, distribution, revocation and exclusion to be simulated on a semi-analytic platform. The platform would allow to evaluate key figures of merit, such as signal acquisition time, availability, continuity, key revocation performance, and security metrics including effects of a potential compromise in terms of duration and exposure.