Date of Award


Degree Type


Degree Name

Bachelor of Science (Hons.)


Faculty of Computing, Health and Science.

First Advisor

Dr. Craig Valli


To aid system administrators in enforcing strict password policies, the use of password cracking tools such as Cisilia (, 2003) and John the Ripper (Solar Designer, 2002), have been employed as software utilities to look for "weak" passwords. John the Ripper (JtR) attempts to crack the passwords by using a dictionary, brute-force or "other" mode of attack. The computational intensity of cracking passwords has led to the utilisation of parallel-processing environments to increase the speed of the password-cracking task. Parallel-processing environments can consist of either single systems with multiple processors, or a collection of separate computers working together as a single, logical computer system; both of these configurations allow operations to run concurrently. This study aims to optimise and compare the execution of JtR on a pair of Beowulf clusters, which arc a collection of computers configured to run in a parallel manner. Each of the clusters will run the Rocks cluster distribution, which is a Linux RedHat based cluster-toolkit. An implementation of the Message Passing Interface (MPI), MPICH, will be used for inter-node communication, allowing the password cracker to run in a parallel manner. Experiments were performed to test the reliability of cracking a single set of password samples on both a 32-bit and 64-bit Beowulf cluster comprised of Intel Pentium and AMD64 Opteron processors respectively. These experiments were also used to test the effectiveness of the brute-force attack against the dictionary attack of JtR. The results from this thesis may provide assistance to organisations in enforcing strong password policies on user accounts through the use of computer clusters and also to examine the possibility of using JtR as a tool to reliably measure password strength.