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.

1. Google to search for "sun jce policy" and click on Java Cryptography Extension (JCE) Unlimited Strength ... - Oracle.
2. Accept the license agreement and download the zipped package.
3. Unzip jce_policy-6.zip where you put it.
4. Inside are two JARs:
   • jce/US_export_policy.jar
   • jce/local_policy.jar
5. Replace JARs on the path jre/lib/security of the same name with these new ones. If I'm using build 38, this path is jdk1.6.0_38/jre/lib/security.

* For the Java 7 solution, Google for "JCE Java 7" or click on Java Cryptography Extension( JCE) Unlimited Strength Jurisdiction .... The download is named UnlimitedJCEPolicyJDK7.zip.

* For the Java 7 solution, Google for "JCE Java 8" or click on Java Cryptography Extension (JCE) Unlimited Strength Jurisdiction Policy Files 8 Download The download is named jce_policy-8.zip.