The first step in algebraic cryptanalysis is to obtain a system of polynomial equations representing a cryptosystem. Even this first step is surrounded by many open questions, such as determining the most effective representation of different components in a cipher. We describe the software package Scrypt, which automates the tedious aspects of this step and allows easy experimentation with different algebraic models and representations. Scrypt separates the task of describing the structure of a cryptosystem from modeling the components algebraically. Symbolic computation is used in this process to delay attaching algebraic models to components, and allow the user to experiment with different algebraic representations of cipher components later.