I found my answer from this webpage. Here. I coped the text from the page if the page ever goes offline. All credit goes to Velenux.
There’s an emergency and you’re trying to log on that ancient KVM/iLO/iDRAC and you’re getting an error like:
net.sourceforge.jnlp.LaunchException: Fatal: Application Error: Cannot grant permissions to unsigned jars.
Find the java.security file. In my case it is located in /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/security/java.security
Then find the row:
jdk.jar.disabledAlgorithms=MD2, MD5, RSA keySize < 1024
Comment it out, copy it, delete the MD5 string.
#jdk.jar.disabledAlgorithms=MD2, MD5, RSA keySize < 1024
jdk.jar.disabledAlgorithms=MD2, RSA keySize < 1024
Save the file. Try again. It should work.