ITPEC FE Morning October 2023 Question 40
Which of the following is a role of a PKI certification authority as a reliable third party?
Explanation
Issuing a certificate that certifies a public key — the certification authority vouches that a public key belongs to a given user or server.
A certification authority checks the identity of the applicant and issues a digital certificate that binds the applicant's name to its public key, signed with the CA's own private key. Anyone who trusts the CA can verify that signature and then trust the public key.
Answer (d)
Why not others:
- •(a) — a user signs his own e-mail with his own private key; the CA does not sign messages on request
- •(b) — returning the accurate time is a time server, for example NTP, or a time-stamping service
- •(c) — the private key is kept secret by its owner and is never sent to the CA, so it cannot be certified
Key rule: Certificates are public documents: they certify public keys, and private keys never leave their owner.
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