X509sertifikaatissa

X509sertifikaatissa refers to an X.509 certificate. An X.509 certificate is a digital document that uses the X.509 public key infrastructure (PKI) standard to verify the identity of an entity, such as a website, individual, or organization. It acts as a digital passport, binding a public key to a specific identity. These certificates are fundamental to secure communication on the internet, particularly for protocols like HTTPS, which enables secure web browsing.

The core components of an X.509 certificate include the subject's public key, information about the subject (like their name and organization), the issuer's digital signature, the certificate's validity period, and a serial number. The issuer is a trusted third party, known as a Certificate Authority (CA), which verifies the identity of the subject before issuing the certificate. This signature ensures that the certificate has not been tampered with and that it was indeed issued by a legitimate CA.

When a user's browser connects to a secure website (HTTPS), it receives the website's X.509 certificate. The browser then checks the certificate's validity, including verifying the CA's signature against a list of trusted CAs stored within the browser or operating system. If the certificate is valid and trusted, the browser establishes a secure, encrypted connection with the website, indicated by a padlock icon in the browser's address bar. This process ensures the confidentiality and integrity of the data exchanged.