Motivation

This application note presents techniques that can be used when securing a design from outside access. Although no design can ever be fully secured it can be constructed such that the effort required to break the security is as high as possible. There is a significant difference between an unsecured design that a person with basic engineering skills can duplicate and a design that only a few, highly skilled intruders can break. In the unsecured case, the design is easily copied and even reverse engineered, violating the intellectual property of the manufacturer and jeopardizing the market potential for the design. In the secured case, the effort required to break the design is so high that most intruders simply focus on developing their own products.

There is only one general rule on how to build a secure system: It should be designed to be as difficult to break as possible. Any mechanism that can be used to circumvent security will be tried during a break attempt. A few examples of what must be considered are given below.