X509sertifikaatti

X509sertifikaatti refers to an X.509 certificate, which is a standardized digital document used to verify the identity of an entity, such as a website, individual, or organization. These certificates are a fundamental component of Public Key Infrastructure (PKI) and play a crucial role in establishing trust and security in digital communications.

The X.509 standard defines the format and content of these certificates. A typical X.509 certificate contains information such as the subject's name, the issuer's name, a public key associated with the subject, a validity period (start and end dates), a serial number, and the issuer's digital signature. This signature is what ensures the certificate's authenticity and integrity.

When a browser or application encounters an X.509 certificate, it verifies the issuer's signature against a trusted root certificate authority (CA). If the signature is valid and the certificate has not expired, the entity presenting the certificate is considered authenticated. This process is essential for secure protocols like HTTPS (HTTP Secure), which encrypts communication between a web browser and a server, preventing eavesdropping and man-in-the-middle attacks.

X.509 certificates are also used in various other security applications, including email encryption (S/MIME), digital signing of documents, and authentication of devices and users in corporate networks. Their widespread adoption makes them a cornerstone of modern internet security and digital trust.