X.509
X.509 is a standard that defines the format for public key certificates, which are used to establish a secure connection between parties over the internet. These certificates contain information about the key, the identity of the owner, and the digital signature of a trusted authority, ensuring that the key belongs to the claimed entity.
The X.509 standard is widely used in various security protocols, including SSL/TLS for secure web browsing and S/MIME for secure email communication. By providing a way to verify identities and encrypt data, X.509 plays a crucial role in maintaining online security and trust.