developerWorks: Most of today's secure communications, including SSL and cryptographic algorithms, rely on the simple mathematical fact that factoring very large numbers is computationally difficult. And by "difficult," we mean that given current computational resources, it would take many years to find the factors (numbers that multiplied by themselves give the original number) of a very large number. Among the many algorithms designed for this task, the quadratic sieve is one of the fastest. In this article, the author provides an OGSA-based, Globus Toolkit 3.0 implementation of the self-initializing quadratic sieve for a grid environment.