X509v3laajennukset

X509v3laajennukset refers to X.509 version 3 extensions. These extensions are optional fields that can be included in an X.509 digital certificate to provide additional information beyond the basic certificate data. They are defined by RFC 5280 and allow for greater flexibility and extensibility in certificate usage.

Common X.509v3 extensions include the Subject Alternative Name (SAN), which allows for specifying additional identities for the certificate holder, such as hostnames or IP addresses. The Key Usage extension specifies the intended purposes of the public key contained in the certificate, such as digital signature or key encryption. Extended Key Usage provides more specific application purposes for the key, like server authentication or client authentication.

Other important extensions include Basic Constraints, which indicates whether a certificate is a Certificate Authority (CA) certificate or an end-entity certificate, and CRL Distribution Points, which specifies the locations where Certificate Revocation Lists (CRLs) can be found. The Authority Information Access extension can point to resources that provide information about the issuing CA, such as its OCSP responder or CA certificate.

These extensions are crucial for modern Public Key Infrastructure (PKI) implementations, enabling a wide range of security applications and policies. They allow for finer-grained control over certificate validation and usage, making X.509 certificates more versatile and secure.