Runnin SSH on slow CPU (386 40Mhz 8Mb RAM)

[Darren Tucker]

Raphael Hertzog wrote:
> I'd like to use OpenSSH (client & server, for shell & sftp) on
> an embedded PC with limited resources (processor 386 SX 40Mhz
> 8Mb RAM). I have Linux running on it.
> 
> In the past, I tried to use OpenSSH on it just to see if it could
> work but each connection required an incredible long time to start. I
> suppose that the key generation is too expensive for that processor.

Run ssh -vvv and you will be able to see which steps are taking the most 
time.

> Is there something I can try to make it work better ? Can we change
> the key length or use another encryption algorythm which is less
> CPU-expensive ? Which one of the available cipher is the less CPU
> expensive ?

Usually arcfour for symmetric ciphers, but it's probably the public-key 
stuff (DH, RSA or DSA) that's killing you.

> Can I change ServerKeyBits in sshd_config without breaking
> interoperability ?

Probably yes (within reason) but that will only affect SSHv1 connections.

> Any inputs point me somewhere where I can look further is welcomed. Feel
> free to point me to the right documentation if such one exists, but my
> search have been unsuccessfull until now (including the search on the
> list archive).

http://www.openssh.com/faq.html#3.3

-- 
Darren Tucker (dtucker at zip.com.au)
GPG key 8FF4FA69 / D9A3 86E9 7EEE AF4B B2D4  37C9 C982 80C7 8FF4 FA69
     Good judgement comes with experience. Unfortunately, the experience
usually comes from bad judgement.