IPA IP 2024 Question 66
A question IPA Japan published in 令和6年度 ITパスポート試験 公開問題 問66, translated into English. ITPEC is based on the same exams.
Which of the following is an appropriate description concerning the role of a CA (Certificate Authority) in PKI?
Explanation
Issuing and revoking public key certificates — a CA vouches that a public key belongs to its owner.
In PKI (public key infrastructure), anyone can publish a public key, so a receiver needs proof of whose key it is. The CA checks the applicant’s identity and issues a public key certificate (digital certificate) binding the public key to the owner, signed with the CA’s own private key. When a key is compromised or no longer valid, the CA revokes the certificate and publishes it on a certificate revocation list (CRL) or through OCSP.
Answer (d)
Why not others:
- •(a) — accessing the Internet on behalf of internal computers is a proxy server
- •(b) — blocking unauthorized access from outside by packet filtering is a firewall
- •(c) — mapping domain names to IP addresses so users reach the right server is DNS
Key rule: A CA does not encrypt or filter traffic; it certifies keys: identity check, issue, revoke.
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This question comes from the past questions IPA Japan publishes, translated into English by ITPEC Practice. ITPEC Practice is an independent study tool and is not affiliated with IPA or ITPEC. See the original paper (PDF) or Report an issue.