Certificaatketenen

Certificaatketenen, often referred to in English as certificate chains, are ordered sequences of digital certificates that establish a chain of trust from an end‑entity certificate to a trusted root certificate authority (CA). Each certificate in the chain vouches for the authenticity of the one that follows it, allowing relying parties to verify the legitimacy of a public key without having to trust each certificate individually.

The chain typically starts with the end‑entity (or leaf) certificate, which belongs to a server, user, or device. This certificate is signed by an intermediate CA, whose own certificate is signed by either another intermediate or directly by a root CA. The root CA certificate is self‑signed and is normally stored in a trusted store on operating systems, browsers, or applications. By traversing the chain and checking each signature against the issuer’s public key, a verifier can confirm that the end‑entity certificate originates from a trusted authority.

Certificate chains are essential in public key infrastructures (PKI) and are widely used in protocols such as TLS/SSL, S/MIME, and code signing. They enable secure communication, authentication, and data integrity across the internet and corporate networks. Validation processes include checking the expiration dates, confirming that none of the certificates have been revoked (via CRL or OCSP), and ensuring that the chain complies with policy constraints like key usage and basic constraints.

Common issues arise when intermediate certificates are missing, when a root CA is not present in the trust store, or when mismatched algorithms are used. Proper chain construction and maintenance are critical for preventing man‑in‑the‑middle attacks and for preserving user confidence in secure services.