[ followups set ]
Joao <firstname.lastname@example.org> writes:[color=blue]
>I'd like to be authenticated in the SSH server side using Putty,
>so, is it possible to use a X509 Certificate?[/color]
PuTTY does not support X.509 authentication with SSH.
(There may be some third-party fork/patch which does so, but I'm not
aware of one.)