In order to implement SSO, I have been working with some IdP and a Shibboleth SP install without being able to answer this question.
On the IdP side I have a few metadata files that describes some applications. Those files can contain a certificate, but if nothing is given, communication works still fine. If I put the same files on the SP side, it still works fine even when putting some random characters as certificate.
Could someone explain to me really how it works and what is the purpose of those X509 certificates in those metadata file (IdP) side?