Extract IC code has already become a widely used technology in the electronic product reverse engineering industry. And all of the microcontroller IC manufacturers have already been aware of the security.

As one of the most useful IC code extraction methods, ultra-violet radiation chip firmware extraction is very high efficiency and effective. As a result of that, once microcontroller IC manufacturer realize that their developed IC code can be extracted by the ultra-violet radiation, they will take effective actions against IC code extraction. Some of the microcontroller ICs encrypt by the memorizer base upon EEPROM, such as 87C51 from PHILIPS microcontroller ICs, which has 64 bits encryption list to strength the protection against security fuse.

In the process of chip binary extraction, even if security fuse be reset, the corresponding bit-stream XNOR in the program flash memorizer list can be extracted. In the PIC16C61 and PIC16C71 from microchip, when the security fuse is working, the content in the memorizer can be encrypted too before crack MCU memory.

And the encryption method is carry out XNOR operation on the upside case and downside case. Even if the encryption method is very effective, engineer can still use toothpick attacks to wipe out part of the memorizer for extract ic code, and the recover the content and code in the list from IC memorizer. As for the old PIC microcontrollers, code extractor needn’t locate and reset the security fuse, because encrypted content and code can be code by proper programmer.