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Interview question · Systems, OS & Memory Safety

What are side-channel and fault-injection attacks, from timing and cache leaks to power analysis and glitching, and how are they stopped?

The algorithm is correct and the key never leaves the chip. The attacker reads it anyway from how long, how loud or how hot the computation is, or breaks it by making the chip skip one instruction.

hardEssentialNewPreparation tags: Apple, Google, MicrosoftUpdated Nov 2026

The algorithm is correct and the key never leaves the chip. The attacker reads it anyway from how long, how loud or how hot the computation is, or breaks it by making the chip skip one instruction.

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What would you say before reading the answer?

  1. 01 State the assumptions your answer depends on.
  2. 02 Explain the mechanism and choose a control.
  3. 03 Name a condition that would change your decision.

The worked answer includes an approach, scoring criteria and follow-up questions. Compare the reasoning with your own.

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What if · the follow-ups in this answer

The answer works through 6 follow-ups like an interviewer would

An API compares a submitted HMAC with the expected value using a normal string equality check, and a hardware product team asks about physical attacks too.

  1. What is a timing side channel here?
  2. How do you fix it?
  3. What other side channels exist?
  4. What is fault injection?
  5. How do hardware products defend?
  6. What would you recommend?

Each rung has a nudge, a model answer, the principle that carries over and the weak answer to avoid. Premium opens every answer and ladder.

UP NEXT ON YOUR JOURNEY
Next in this trackHow do white-box crypto, DRM and licensing try to protect secrets on devices the attacker owns, and where does each break down?Next in this trackExplain macOS platform security: Gatekeeper, quarantine and notarisation, SIP and the sealed volume, TCC, and how attackers get around them.Next in this trackHow do Windows, Apple platforms and Linux enforce code signing at install, load and run time, and how is it circumvented?
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