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Interview question · Network Security & Protocols

What does message signing do in SMB, LDAP, IPsec, DNSSEC and MACsec, and when is signing the right choice instead of encryption?

Signing does not hide anything. It proves who sent a message and that nobody changed it, which is exactly what relay and tampering attacks need you not to check.

mediumEssentialNewPreparation tags: Microsoft, Cisco, Palo Alto NetworksUpdated Nov 2026

Signing does not hide anything. It proves who sent a message and that nobody changed it, which is exactly what relay and tampering attacks need you not to check.

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  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.

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What if · the follow-ups in this answer

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

An internal network still allows unsigned SMB and LDAP, and a red team reports relaying a server's authentication to the domain controller.

  1. What does signing provide?
  2. How does SMB signing stop relay?
  3. What about LDAP?
  4. How do you roll this out without breaking things?
  5. What else reduces relay risk?
  6. What remediation would you propose?

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