Reversing Stealthy Dopant-Level Circuits
stef
s at ctrlc.hu
Mon Jun 30 10:53:48 PDT 2014
http://eprint.iacr.org/2014/508
> Abstract: A successful detection of the stealthy dopant-level circuit
> (trojan), proposed by Becker et al. at CHES 2013, is reported. Contrary to
> an assumption made by Becker et al., dopant types in active region are
> visible with either scanning electron microscopy (SEM) or focused ion beam
> (FIB) imaging. The successful measurement is explained by an LSI failure
> analysis technique called the passive voltage contrast. The experiments are
> conducted by measuring a dedicated chip. The chip uses the diffusion
> programmable device: an anti-reverse-engineering technique by the same
> principle as the stealthy dopant-level trojan. The chip is delayered down
> to the contact layer, and images are taken with (1) an optical microscope,
> (2) SEM, and (3) FIB. As a result, the four possible dopant-well
> combinations, namely (i) p+/n-well, (ii) p+/p-well, (iii) n+/n-well and
> (iv) n+/p-well are distinguishable in the SEM images. Partial but
> sufficient detection is also achieved with FIB. Although the stealthy
> dopant-level circuits are visible, however, they potentially make a
> detection harder. That is because the contact layer should be measured. We
> show that imaging the contact layer is at most 16-times expensive than that
> of a metal layer in terms of the number of images
--
otr fp: https://www.ctrlc.hu/~stef/otr.txt
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