A membership service provides information about faulty nodes (e.g. nodes not
synchronized with the global time) which is vital for safety-critical
applications. FlexRay does not provide a membership service by design, hence it
must be implemented on the application layer. Openness and connectivity of
real-time systems have increased over the years, thus a logical step forward is
this service. Clock synchronization is the most elementary and
therefore most vulnerable operation in a time-triggered protocol. By using a
secure membership service, we also secure the concerning clocks. On top of that,
other services can be realized on a higher layer.
We have implemented the secure membership service on a FlexRay evaluation board
("bitspot blue" by Fujitsu) by using two different approaches:
- symmetric encryption only (AES)
- symmetric encryption in combination with public key cryptography (RSA-AES)
We have analyzed both implementation variants with several parameters (key size and frequency)
with respect to computation time and memory usage.