Hardware Security

Which method is commonly used to store keys written into a chip?

  1. AOne-time-programmable eFuses or OTP memory, or storing them encrypted in non-volatile memory
  2. BPrinting the key value on the chip surface
  3. CPlacing the key value as is in memory anyone can read externally
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Answer: A. One-time-programmable eFuses or OTP memory, or storing them encrypted in non-volatile memory

An eFuse is one-time-programmable storage written bit by bit by blowing a thin wire with a large current. Per-device keys and settings are written after manufacturing, sometimes made unreadable by software so that only the cryptographic engine can use them. Another approach stores keys in flash encrypted with a key derived from a PUF. In every approach, restricting read paths is essential.

  • A. Correct. Read restrictions and combination with PUFs are also used.
  • B. Anyone looking would see it.
  • C. The key would be stolen immediately.
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More Hardware Security questions

  1. Besides speed, what advantage comes from giving CPUs dedicated AES instructions (such as AES-NI)?
  2. What must be observed when implementing cryptographic code in constant time?
  3. What is the idea of partitioning a shared cache as a countermeasure to cache side channels?
  4. Why do some systems handling confidential work disable the CPU's simultaneous multithreading (SMT)?
  5. What countermeasure protects against external devices connected to a PC using DMA to read or write main memory without permission?