I cannot get application link between Jira and Confluence to work since I upgraded to HTTPS (port 8443). I am using a keystore referenced in the server.xml file. I added Confluence's certificate in the Jira keystore (and vice versa).
Here is the error message from Jira :

With the associate log error :
Unable to perform a request to: https://jira-agile.fr.cly:8443/rest/gadgets/1.0/g/messagebundle/en_US/gadget.common,gadget.average.age
javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)
...
And the error message in Confluence :

It looks like a certificate error, maybe have I missed a step ?