OK genius, you suggest something that NO ONE can break! I'm sure the
CIA, FBI, MI-5 and the Mafia would all love to know about it.
Hmmm... A RAM-based FPGA (something like a Xilinx XC3000 or XC4000
series), battery-backed supply, configured, and then the configuration
memory removed should keep you guessing...
Removing the fevice from the board would lose the configuration, and I
doubt if you could remove the encapsulation without losing it either.
Actually, reverse-engineering an FPGA from the configuration data is a
non-trivial task as the format of said data is undocumented.
-tony