Networking interview question · Most asked
What does TLS provide, and how does certificate validation work?
Summary
TLS provides encryption, integrity and server authentication. The server presents a certificate for its name, plus intermediates; the client checks the name, validity dates and that the chain leads to a trusted root CA, and the server proves it holds the private key during the handshake.
Longer Answer
TLS 1.3 completes the handshake in one round trip and only allows forward-secret key exchange. Common failures: expired certificates (automate renewal with ACME, ACM or Key Vault), hostname mismatch, missing intermediates (browsers may cope, other clients fail) and private CAs not trusted by clients. mTLS adds client certificates for service-to-service authentication.
Key Points
- Encryption, integrity, authentication.
- Name, dates and chain to a trusted root.
- Serve the full chain.
- Automate renewal and monitor expiry.
Deep dive: Networking Tutorial: HTTPS and TLS
Explanation
What interviewers look for
Understanding of the chain of trust and of real-world failure modes.
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