In the old days, EPROM parts and OTP (one-time-programmable) parts were often the exact same die. The only difference was the window in the package. Hardware se

In the old days, EPROM parts and OTP (one-time-programmable) parts were often the exact same die. The only difference was the window in the package. Hardware security measures are never absolute; but no one who has thought more than briefly about it would use a UV-erasable bit to protect an important secret. "Direct" tampering with hardware is always possible, but for a recent design it will be extraordinarily expensive--electron microscopes, FIB, and so on. The interesting exploits are usually mistakes in the logic, the power supply sequencing, etc., not direct attacks on the memory cell. There's maybe some analogy with software security, where practical attacks on a (well-known) crypto algorithm are incredibly rare, and practical attacks on everything around it are incredibly common.