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Interview question · Mobile Application Security

How are mobile apps signed and verified: APK signature schemes and key rotation, and iOS certificates, profiles and entitlements?

On a phone, the signing key is the app's identity: it decides who can ship updates, which data the app can share, and what it is entitled to do. Lose it, or let someone else sign, and that identity changes hands.

mediumNewPreparation tags: Google, Apple, MicrosoftUpdated Nov 2026

On a phone, the signing key is the app's identity: it decides who can ship updates, which data the app can share, and what it is entitled to do. Lose it, or let someone else sign, and that identity changes hands.

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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

A mobile team ships apps on Android and iOS and asks what signing actually protects.

  1. How does Android signing work?
  2. Why did signature schemes change?
  3. How does iOS signing and provisioning work?
  4. What does signing not protect?
  5. How should signing keys be protected?
  6. How would you explain and protect signing?

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