If you're using OpenJDK, which is what Ubuntu distributes by default since Oracle stopped the practice of licensing the use of its JVMs, you do NOT need to bother with any of this. However, as soon as you start using a proper Sun JDK from Oracle, you'll start having trouble using some higher-order hashing or encryption solutions.
Note that in the procedure below, we're getting a solution for Java 6. The solution for Java 7* is slightly different. Do not mix JARs for Java 6 into a Java 7 JDK/JRE.
* For the Java 7 solution, Google for "JCE Java 7" and click on Java Cryptography Extension( JCE) Unlimited Strength Jurisdiction .... The download is named UnlimitedJCEPolicyJDK7.zip.