4 ms·
Maybe! I've got some experience with tomographic algorithms, and what they're referring to is correcting for the "missing wedge" in the Radon and/or Fourier tra
by heyitsguay 7y ago
Maybe! I've got some experience with tomographic algorithms, and what they're referring to is correcting for the "missing wedge" in the Radon and/or Fourier transforms - the measurements that tomography produces - of the chip (https://images.app.goo.gl/HWPX2LKBsDd7eeBe6 https://images.app.goo.gl/HWPX2LKBsDd7eeBe6). There has been lots of interest in statistical or data-driven algorithms to reconstruct missing measurement areas from the existing ones. It sounds like a key technology here was better algorithms to accommodate a larger missing wedge, so they didn't have to tilt the chip to extreme angles when getting projections.
It's possible you could fool the algorithm in some way, but you'd have pretty weird and severe constraints on the shapes of your hidden parts to hide their presence from low-angle projections. They're probably not actually hand-crafting geometric assumptions about chip structures or anything like that.
- kardos 7y agoYep that's exactly the idea. Basically the silicon version of the underhanded C contest [1] [1] http://www.underhanded-c.org/ http://www.underhanded-c.org/
- heyitsguay 7y agoCool! Know of any websites or writeups about the silicon version?
- kardos 7y agoUnfortunately no but it would be highly interesting to read!
- abbeyj 7y agoSome anti-reverse-engineering work was put into the Z80 chip 45 years ago. 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-...
- Taniwha 7y agoBefore 1984 there was no copyright on the contents of chips, it was completely legal to create masks from a competitor's chips and sell them - people used to create on-chip structures designed to fool the optical processes that were used to do this