The stamps have a threaded bolt hole machined into them for this very purpose! We actually built a system very similar to what you describe (secure space acces

The stamps have a threaded bolt hole machined into them for this very purpose! We actually built a system very similar to what you describe (secure space access authentication) at the TechCrunch Disrupt Hackathon in SF back in September. Our project (amazingly) won the whole damn hackathon: http://snow.sh/ack http://snow.sh/ack