Tools / Cyber Security Interview Questions
Explain the lifecycle of a Digital Certificate in PKI?
- Key generation: the entity generates a public/private key pair
- Certificate Signing Request (CSR): the entity submits its public key and identity details to a Certificate Authority
- Validation: the CA, sometimes via a Registration Authority, verifies the requester actually controls the domain or identity claimed
- Issuance: the CA signs the certificate, binding the public key to the verified identity
- Deployment: the certificate is installed on the server and presented during TLS handshakes
- Renewal or revocation: the certificate is renewed before expiry, or revoked early if the private key is compromised, and added to a Certificate Revocation List or checked via OCSP
Clients validate a certificate by checking the CA's signature, confirming it hasn't expired, and checking that it hasn't been revoked, before trusting the public key it contains.
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