Encrypted code:

Here is a new product Idea for the microcontroller manufacturers...
Add a non-volotile externally programmable register set (128 bits) which is used as an decryption key. The decryption key is used to internally translate encripted code data to its true value.

So, a manufacturer can distribute encripted code and code changes without much worry of the code being reverse-engineered. Each microprocessor has its decryption key manually programmed at the factory to the same key value and then can understand the encrypted code.
Without such a technique, it is simple to look at any external code.

The big issue is making a decrypting algorithm that can quickly translate the code, and one that isn't expensive.

This is possibly impractical costwise. One of the big benefits is allowing a product to have a source update without also allowing someone to understand the update images. The intended target (that has the correct decryption key) is the only thing that works with the code.

<>< Lance.