About Crypto

The recent discussion on fingerprints here has got me wondering as I have never 
really got around to it myself. I know little and about security and most i 
have aver done is created a public private key (rsa) for my company gitosis 
git hosting (ssh).

I would like to sign mail and perhaps even encrypt some of my office mail and so 
would like to learn a little. Of course, i am interested in this from a user 
point of view. I would really appreciate anyone educating me on this... maybe 
just point me to relevant web links!

Clearly, kmail has support for these. so let me ask.

1) Can I use the same key that I generated for ssh access to my company git 
hosting server? I would prefer to keep one key for all official work.

2) Do I need to back up this key and keep it real safe? As far as my ssh 
access is concerned it is not fatal if I loose the key as all i need to do is 
inform colleagues and then regain access to the server with help from a 
coleague who can reset my ssh key on the server with a new one. I guess I will 
need to backup especially for encrypted mail! :)

3) What do the recipients of my mail need to do? I can help with colleagues 
but probably not so with external people if it requires them to perform 
something complex before they can read my mail. What would they need to do?

4) How do commonly used clients like outlook and even web clients like gmail 
deal with it?
-- 
Cheers!
Kishore