This research is concerned with distributed parallel processing and how a computer cluster/network may be used to solve large and computationally expensive problems, specifically in the area of cryptography and the problem of factoring very large numbers. Until recently few methods or systems were capable of harnessing the full potential power of a distributed environment. In order to realise the full potential of computer clusters, specially designed distributed parallel processing systems are needed. Cryptography is the science of secure communications and has recently become commercially important and widely used. This research focuses on public key cryptography, the security of which is based on the difficulty of factoring extremely large numbers. The research described in this thesis covers parallelism and distributed computing and describes an implementation of a distributed processing system. An introduction to cryptography is presented, followed by a discussion on factoring which centres on describing and implementing a distributed parallel version of Lenstra’s Elliptic Curve factoring method.