Välisertifikaatti

Välisertifikaatti, or intermediate certificate, is a document issued by a certification authority that vouches for the authenticity of another certificate. It acts as a link in a chain of trust, connecting a server's or user's certificate back to a trusted root certificate. When a web browser or other client application encounters a certificate, it verifies its validity by checking the entire chain of trust. This chain typically consists of the end-entity certificate (e.g., a website's SSL/TLS certificate), one or more välisertifikaatti, and finally, a root certificate.

The purpose of a välisertifikaatti is to delegate the authority to issue certificates. Instead of the highly secured root certificate issuing every single certificate, the root can authorize intermediate authorities to do so. This allows for better management and scalability of certificate issuance. If an intermediate certificate is compromised, it can be revoked without invalidating all certificates issued by the root certificate. This hierarchical structure is fundamental to how public key infrastructure (PKI) operates, ensuring that digital identities can be reliably authenticated across the internet. Browsers and operating systems come pre-loaded with a list of trusted root certificates, forming the foundation of this trust model.