SSH authentication key

[Huaer XC]

Hi,
I am using a Linux server to maintian a package with CVS, other ppl
can access to the repository by SSH. Now that I can generate
SSH-authentication keys by "ssh-keygen" of Linux, or by some Windows
clients, like WinSSHClient(www.ssh.com). My question is if or not I
can keep more than one key on my server, i.e., every user has his/her
own key, and if so how to configure? Also it seems to me that I can
only use root, say "su", to run ssh-keygen, otherwise, the keys are
something like "?", and "?.pub".... Is there anything wrong??

I am very new in this field, please advise me, many thanks..

XC