I have this problem with CAS 7.1 but not only with some installation.
Precisely, with Tomcat 10.1 and JRE Microsoft Jdk 21.0.5.11-hotspot, the problem doesn't arise.

Conversely, with Tomcat 10.1 and OpenJDK 21 the problem is there.

As already said, it can be solved etiher:

• setting cas.webflow.crypto.enabled=false

• or, setting cas.webflow.crypto.encryption.key-size=128 (please note key-size instead of keySize and 128 instead of 32)