On 7/28/2010 1:50 AM, Mikael Abrahamsson wrote: > On Wed, 28 Jul 2010, Yaakov Stein wrote: > >> Yes, the symmetric key stuff is now done in hardware >> but the public key part for authentication is still done in software. >> And due to interactions between the software and hardware, >> requesting authentications can slow down other existing timing flows. > > What about just signing it the way it's done in DNSSEC, ie you have a > certificate/key and each packet is signed before being sent out? >
Yes, we do that in NTP autokey. It's much simpler to do. The main issue there is that you need to provision the clients with keys in order to validate the signature. >> So in principle I can mount an attack by requesting authentications >> using successively "harder" keys followed by successively "easier" >> ones, thus adding hard-to-remove wander to the other timing flows. > > In an multicore multithreaded environment, is this really that huge of a > problem? Also if we count in that people who are really interested in > this might have a device with a separated control plane and "data plane" > just like high capacity routers are done as of 10 years approximately? The perhaps surprising answer to this is yes, it is a problem in multicore environments because each core has its own clocking and which core's clock you use to timestamp makes a difference. We get lots of jitter this way with NTP. We've had lots of discussions about this in NTP. Danny _______________________________________________ TICTOC mailing list [email protected] https://www.ietf.org/mailman/listinfo/tictoc
