Hardware Security
What is the idea behind masking, a countermeasure against power analysis?
- ACovering the chip surface with tape to hide it
- BIntermediate values are combined with a fresh random number each time to hide them, breaking the link between power consumption and secret values
- CUsing the same cryptographic key in every device
Show answer and explanation
Answer: B. Intermediate values are combined with a fresh random number each time to hide them, breaking the link between power consumption and secret values
Power analysis exploits correlations between intermediate values and power consumption. With masking, an intermediate value x is never handled directly but represented combined with a freshly generated random m (for example x XOR m), and the correct result is recovered at the end. The values the circuit actually handles change randomly each time, obscuring the correlation between power and secrets. Good randomness and circuit designs that never expose unmasked values are essential.
- A. It is not physical covering.
- B. Correct. Even with the same key, different values are processed each time.
- C. A shared key puts every device at risk if one is analyzed.