SSH for small uPs

The private key encryption could take minutes on an AVR. Try something with more power and a hardware multiplier, like the larger MSP430's.

Client or server? I don't know of any cross platform servers (they tend to be mixed up with things like terminals and processes on the host machine) but there are some cross platform ish clients - for example PuTTY (Free):

Whilst the front end is tied to Windows, the backend is fairly easy to extract and use separately.

8 bit would be pushing it. A statistic I heard is that a 386 could do 5Mbits/sec blowfish at full tilt under Linux - but key exchange is probably going to be the slow bit (my Linux 386 OpenSSH server took a minute or two, literally, to do a login - though it had 4MB of RAM so had to swap a fair bit). My feeling for this (based on a bit of experience and a lot of guessing) is that a 68K or 386 class CPU would be a reasonable minimum. I'd say you need C as a basic minimum unless you feel like handcrafting this in assembler (it's about the same complexity as writing a TCP/IP stack except there aren't as many shortcuts).

Theo

--
Theo Markettos                 theo@markettos.org.uk
Liphook, Hampshire, UK         theom@chiark.greenend.org.uk
                               http://www.markettos.org.uk/

You should look at 16 bits integer DSPs for the public key cryptography computations. The general purpose processor that will do your protocol does not have the right instruction set ("hardware multiplier" is a small portion of the solution) for decent speed for key setup.

- Thierry Moreau