Certificate-based authentication

is a way of verifying the identity of a user or a server based on public key cryptography.

uses a public and a private key (files)
public key – can be shared with anyone (ex: browser client)
private key – is kept secret by the owner (ex: web site)
similar to electronic passports (they have a private key)
the owner can use the private key to sign a message
anyone who has the public key can verify that the message was signed by the owner
authentication certificates are issued by trusted authorities (certificate authorities (CAs))
CAs verify the owner’s information, name, certificate details, criminal records, taxes, domain, IP
It is common to use with TLS/SSL protocol (HTTPS)
SSL uses digital signatures to establish a trust relationship between the sender and receiver