The modern assembly systems are fully integrated production systems. They consist of interconnected components of hardware and software. Large flexible assembly systems are being composed of high number of components and managing requires an enormous volume of data. For that reason the controlling and optimization of such systems is too complex. Nowadays that can achieved, using just computers and software tools. In this paper the optimization of product mix for assembly system for electric motors will be described. Also special attention will be given to data security of the information system using cryptography.