Among fault injection attacks, which correctly pairs the characteristics of methods using a laser and methods using electromagnetic pulses?

Answer: A. A laser is often shone with near-infrared light from the back of a decapsulated chip and can target places very precisely. EM pulses are applied with a coil and sometimes work without decapsulation, but the area they affect is relatively wide

The bandgap of silicon is about 1.12 eV, and light with wavelengths longer than about 1.1 µm is hardly absorbed. Near-infrared light around 1 µm is only weakly absorbed, so it penetrates deep from the back of a thinned substrate and is partly absorbed near the transistors, creating electron–hole pairs. The front side is covered by many metal wiring layers, so laser fault injection usually shines from the back, using the photocurrent to make specific transistors or SRAM cells malfunction. With EM pulses, a large current is passed through a coil briefly to create a strong change in magnetic field, which induces voltages in the chip's wiring and power grid and causes malfunctions. Countermeasures combine sensors that detect light or electromagnetic fields, duplication of critical computations and mechanisms that erase keys when errors are detected.

• A. Correct. Lasers stand out for precise targeting and EM pulses for the convenience of not needing decapsulation.
• B. A laser generally requires decapsulation, while EM pulses sometimes work without it, so this is close to the reverse.
• C. Neither melts anything with heat; both cause temporary malfunctions through charge or induced voltage.