Interception is one thing, but I'm pretty sure that covertly interfering with the link (injecting data both ways, for a long-ish time) would be pretty interesti

Interception is one thing, but I'm pretty sure that covertly interfering with the link (injecting data both ways, for a long-ish time) would be pretty interesting... Yes, it could be encrypted using low-latency HW implementations. However, I'd be surprised if these actually perform all the necessary steps to establish a truly secure link (like use message authentication besides encryption, and such).