How to guess how to add the key of a repo (GPG, apt-key add,...)

[Mihamina Rakotomandimby]

Hi all

I have to use a repo: http://open.iabsis.com/debian/
When adding it in my sources, apt complains about not having GPG key 
about it.
Would you know how to guess the gpg invocation (server, key,...) in 
order to import it to apt?

Thank you.