If you use Sun JDK6 to run Java apps such as Atlassian Confluence (the page you're looking at now), JIRA, etc, via HTTPS, you might have noticed that your browser will not negotiate any ciphers stronger than 128 bit. What is the problem here?
The apps themselves by default do not do anything with crypto, the issue is with the so-called policy files of JDK6. According to Sun:
Due to import control restrictions for some countries, the Java Cryptography Extension (JCE) policy files shipped with the Java SE Development Kit and the Java SE Runtime Environment allow strong but limited cryptography to be used.
From the Sun website, download the JCE Unlimited Strength Jurisdiction Policy Files 6 Release Candidate.
Unpack the ZIP file - it will contain two jar files: local_policy.jar and US_export_policy.jar.
On our Ubuntu boxes we use the packages sun-java6-jdk, sun-java6-bin, and sun-java6-jre. The files in question are stored in /usr/lib/jvm/java-6-sun/jre/lib/security.
Replace the two jar files and restart your Java app.
Your browser should now be able to negotiate 256 bit ciphers.