If you want to use keys longer than 256 for cryptography in Java, you will have to install the JCE Unlimited Strength Jurisdiction Policy. It adds support for bigger keys.
But there is a much simpler way to do this on Linux. Some distributions like RHEL / CentOS or Ubuntu come with unlimited strength JCE build into their own OpenJDK packages.
On Ubuntu install the OpenJDK 7 package:
sudo apt-get install openjdk-7-jre-headless # on server sudo apt-get install openjdk-7-jdk openjdk-7-source # on developer machine
On RHEL 6 / CentOS 6 install the OpenJDK 7 package this way:
yum install java-1.7.0-openjdk # on server yum install java-1.7.0-openjdk-devel # on developer machine
Both have unlimited encryption build in. You can verify it with a simple code snippet