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Stealthy Dopant-Level Hardware Trojans (2013) [pdf]
- Arrath 6y agoWell this is certainly eye opening, and a new level of insidious technical wizardry to me.
- userbinator 6y agoI'm a little surprised the authors didn't mention that this technique was used to obfuscate the Z80 with several "trap transistors": https://www.cl.cam.ac.uk/~sps32/Z80proj/Z80_traps.pdf https://www.cl.cam.ac.uk/~sps32/Z80proj/Z80_traps.pdf As the above images, and the presence of many Soviet clones shows, the obfuscation was not entirely impossible to detect.
- rkagerer 6y agoSo if I understand this correctly... They under-doped certain areas to create depletion mode transistors that any reverse engineer examining the silicon would expect are regular enhancement mode ones. They strategically placed a handful of these "disguised" transistors, which once incorrectly copied would switch in the opposite manner and wreak havoc on circuit operation. According to one of the designers[1]: I heard from NEC later the copy maker delayed the announcement of Z80 compatible product for about six months. [1] https://retrocomputing.stackexchange.com/questions/11143/in-the-original-z80-layout-where-are-the-traps-located-and-what-are-their-ef https://retrocomputing.stackexchange.com/questions/11143/in-...