Hardware Security

What is the basic mechanism of Arm TrustZone?

  1. AAll secure processing runs on a separate PC
  2. BNormal-world programs can freely read secure-world memory
  3. CThe CPU has secure-world and normal-world states, and bus signals distinguish which world each memory or peripheral access comes from, enforcing restrictions
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Answer: C. The CPU has secure-world and normal-world states, and bus signals distinguish which world each memory or peripheral access comes from, enforcing restrictions

In TrustZone, a CPU core switches between secure and normal states, and every access carries a bus signal indicating which state issued it. Logic on the memory and peripheral side checks this signal and rejects normal-world accesses to regions assigned to the secure world. It creates a secure area within a single SoC without an extra chip, so it is widely used in smartphones and similar devices.

  • A. The separation is within the same chip.
  • B. The normal world is prevented from reading it.
  • C. Correct. The same CPU is shared between two worlds.
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More Hardware Security questions

  1. What characterizes enclave-style TEEs such as Intel SGX?
  2. In confidential computing on the cloud, what is the purpose of CPU features that encrypt virtual machine memory (such as AMD SEV or Intel TDX)?
  3. Which describes a PUF (physically unclonable function)?
  4. What is the advantage of using a PUF for key storage?
  5. What property does an SRAM PUF exploit?