ISC Cryptography · Updated November 2026
What Does a Certificate Authority Actually Certify?
PKI helps users trust that a public key belongs to the claimed identity.
Digital certificate
A certificate connects identifying information with a public key under an established trust framework.
Certificate authority
A CA issues and signs certificates after performing the applicable validation.
Trust chain
Systems can trust a certificate because they trust the root and intermediate certificate authorities in a valid chain.
Revocation
Certificates can need revocation before expiration when a private key is compromised, information changes, or issuance was improper.
The takeaway
A certificate does not make a public key secret. It binds identity information to a public key within a trust framework.
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FAQ
Is a public key supposed to remain secret?
No.
Does the CA normally hold every user's private key?
No.
Can certificates be revoked?
Yes.