[dboreham]

Not being able to read the key material with a microscope (optical or electron) is a specific design goal for these things. This takes me back more than 30 years to my very first job, the summer between high school and college. I had to disassemble and modify a number of crypto units used in the banking industry. These things had all sorts of mechanisms to make it hard to access the key, including zapping the EPROM containing the key with very high voltage if any of the case intrusion switches were tripped. My boss cheerfully informed me that the previous model had used a small explosive charge, and this new one was a safer alternative!