On Sat, 28 Aug 1999, my inner geek wrote:
> Having thoroughly established that I'm a confused layperson in
> technology areas, may I humbly request an explanation of the "active
> shield" concept mentioned in "Engines of Creation?"
I haven't read this in a while, but I think an active shield is one that response actively to a threat. Like a fabric that is very soft under normal conditions, but upon sensing a sharply penetrating force, becomes as strong as steel. It is kind of like the airbag in a car. This could also be done with a flying swarm of nanobots in close proximity to your body. These are discussed a little bit in Nanomedicine.
> Once it is known that nanomachines are in use in a particular product
> or person or object, what is to prevent the object from being frozen
> then destructively scanned by SPM/AFM for structure?
Well this is one of the unresolved areas in nanotech. One suggestion is for the machines to disassemble themselves on intruder detection. You can easily sense if your temperature is being abnormally lowered and warm yourself up to normal temperature or disassemble. I'm fairly sure that a nanobot could detect itself being X-rayed and actively respond. I doubt that there is any exploratory method that you could use that the nanobot could not detect. Remember all of those methods they used to hide evidence in Mission Impossible? They only get fancier in the nanotech world.
> In other words, if Johnny Mnemonic has a nice nano vr system in his
> head, wouldn't there be many parties who wan't Johnny's head on a
> silver platter, to study the hardware inside?
Reverse engineering nanotech? Possibly, its done fairly frequently in the microproccessor and software industries. But I suspect if you really want to keep the design secure, it can be done. Since most nanotech designs are likely to be open source, then its a rare piece of nanotech you are going to want to take apart.