basic question about authentification

["Yvon Thoraval" <yvon.thoraval () gmail com>]

Hey all,

new to ssh and scp I'm doing files upload|download from a personal
computer to an handheld mobile phone.
on the computer side i'm using OpenSSH as installed by Apple Mac OS X 10.4.11.
on the other, an e2831 phone named "Twin-Tact" running QTopia, I've
installed by myself dropbearmulti for ssh and the like.

the connections are working well, and my questions are more for my
understanding.

let me tell you some experiments :

If i do :
$ ssh -p 2222 root@169.254.0.2
Enter passphrase for key '/Users/yt/.ssh/id_dsa':
Permission denied (publickey).

then, i'm rejected, however, with the same passphrase and using
ssh-agent like that (from command line) :

$ eval `ssh-agent -s`
Agent pid 2044
$ ssh-add ~/.ssh/id_dsa
Enter passphrase for /Users/yt/.ssh/id_dsa:
Identity added: /Users/yt/.ssh/id_dsa (/Users/yt/.ssh/id_dsa)
$ echo $SSH_AUTH_SOCK
/tmp/ssh-kbqXlJAxOy/agent.2043
$  ssh -p 2222 root@169.254.0.2
   _______  _______      _______  _______  _______  __       _______
  |       ||       |    |__   __||   _   ||   _   ||  |     |   ____|
  |__   __||__   __| ___   | |   |  |_|  ||  |_|  ||  |____ |____   |
     | |      | |   |___|  |_|   |_______||_______||_______||_______|
     |_|      |_|               Bienvenue sur le Twin Tact !!!
Last login: Tue Jul 22 08:31:35 UTC 2008
# exit
Connection to 169.254.0.2 closed.
$

then, here , using ssh-agent, i don't get the insane ( ;-) )
"Permission denied (publickey)" why ?

third and last experiment, now i'll log as root to my computer i enter :

$ su root
www:/Users/yt/Desktop root# scp -P 2222 net-scp.rb
root@169.254.0.2:/mnt/fat/net-scp.rb
Enter passphrase for key '/var/root/.ssh/id_dsa':
net-scp.rb

   100%  161     0.2KB/s   00:00

being under root account, on the computer side, works without having
to use ssh-agent.

i wonder if the reason as something to do with the account being of
same name both sides "root" ?

in any case i'll have to use a persistent way, the ssh-agent
$SSH_AGENT_PID will be cached in a file, however, for my understanding
i'd like to know the reasons for such a behaviour.

could that be due to a misconfiguration of mine ?

best,

-- 
yvon