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Flipping read-protect bits: Altera EP900 | Kibotronics

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Techniques used to locate and erase on-silicon security bits via nitric acid decapsulation, uv masking and binary search.

Introduction Code Protection is a feature offered by microcontrollers to disable storage readout. A developer would typically enable it before the programmed chip lands on customer hands; in principle, disabling code protection would require full erasure of the stored firmware. Typically, code protection state is stored as a bit in on-board storage, in a dedicated area that can be programmed along with the firmware. The code protection machinery itself is established in bootrom or by a dedicated circuit, or sometimes both.1 The Altera EP900 is an old chip, so it seemed like a reasonable…

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