IssueTableau Server set up for mutual SSL authentication will not allow authentication of users with client certificates that have an insecure key attribute. Additionally, upgrades to Tableau Server 2021.1 or newer may fail because of invalid root Certificate Authority.
One of the following errors may be present in the vizportal logs:
Elliptic Curve size does not meet the required min allowed curve size
Key size is smaller than the min allowed key size