IPA IP 2026 Question 90
A question IPA Japan published in 令和8年度 ITパスポート試験 公開問題 問90, translated into English. ITPEC is based on the same exams.
Which of the following is an appropriate characteristic of PKI (Public Key Infrastructure)?
Explanation
A certification authority guarantees the digital certificate — PKI rests on a trusted third party that vouches for who owns each public key.
In PKI, a certification authority (CA) checks the identity of an applicant and issues a digital certificate that binds the applicant to their public key, signed with the CA's own private key. Anyone who trusts the CA can verify that signature and so trust the public key in the certificate. The CA also revokes certificates (for example when a private key is leaked) and publishes the revocation list.
Answer (c)
Why not others:
- •(a) — PKI manages public keys of public key cryptography; a common (shared secret) key is never published, so there is no owner to confirm through a public framework
- •(b) — trusting keys signed by acquaintances is the web of trust of PGP, a decentralized alternative to PKI's central certification authorities
- •(d) — a private key must never be made public; only the public key is published, in the certificate
Key rule: PKI = public key + digital certificate + certification authority; the CA's signature on the certificate is what lets a stranger trust that a public key belongs to its stated owner.
Security · AI-written, may contain errors
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.