One of the most frequently used formats is the X.509 certificate. This includes the public key, signature, and other identifying information about both the sender and the CA who issued the certificate.
One type of X.509 is the SSL/TLS certificate, which secures websites using the HTTPS protocol. SSL stands for “secure socket layer,” and it’s the precursor to TLS, which stands for “transport layer security.” Both of these work by creating an authentication process known as a “handshake” between two devices to establish that they’re both legitimate.
These certificates include a public key, the registered domain name, the name of the business, and identifying information about the CA. As long as the certificate is signed by a trusted CA (there are about 50 of them around the world), you can feel secure in your level of protection.