Alan,

Regarding scrambling the address and data lines, I saw a clever implementation of this about 12 years ago. They had a micro with external EPROM and an ALE type latch.

What they did clever was to substitute the normal ALE latch with an equal pinout programmable logic chip. They were actually scrambling the address lines inside that chip which first deduction ASSUMED was a standard latch.

Often the best deception is to lead one to their own preconceptions. :)

-Jay C. Box