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You need the certificate to upload it in your SAP system after you finished the set up on Jira side. You can find the documentation for this steps on the page https://crossalm2.atlassian.net/wiki/spaces/JSMIJXFB/pages/65516667056574243973/CC4+-+Set+Up+-+SAP+Side#MaintainSAP#Maintain-https-certificate-in-STRUST