elseAug 2, 2024
DJ🌞

It's been a while since last #nakeddiefriday so here we go.

Today's exhibit comes from a German payphone card (remember them?). Infineon M2332-B1. What is interesting, is the decision to fill as much top metal as possible, making the die look very much like hobby-made milled PCBs.

More: https://siliconpr0n.org/archive/doku.php?id=infosecdj:infineon:m2332-b1

N.B. If you look closely, you will find a sun. 🌞

#reverseengineering #electronics #microscopy #icre

infosecdj:infineon:m2332-b1 [Silicon Pr0n]

Aug 2, 2024 at 9:04amWeb
Show threadMichałAug 2, 2024
@infosecdj Dummy fill is pretty common to ensure minimum density. It's a necessity when the process uses chemical-mechanical polishing.
Show threadDJ🌞Aug 2, 2024
@RicoElectrico fair point. though I can't say this specific chip has been through the polishing process as the layers below metal are obviously not planar. especially given the "sensitive nature" of the application, I think they did it to annoy reverse engineering people. not that it was a major success.
Show threadPhil M0OFXAug 2, 2024
@infosecdj @RicoElectrico I think more likely they did it to reduce etch chemical exhaustion rates and improve yields. As a side effect the EPROM ends up covered in metal, which makes it harder to do UV erase attacks.