Digital certificates are mainly used to secure online transactions. Some of the typical applications of this public key cryptography method are:
SSL
Secure Sockets Layer (SSL) uses digital certificates for server authentication, key exchange, and client authentication, which are processes critical in determining whether a message sender is who he/she claims to be. This protocol is commonly used in web servers to secure connections between browsers.
Email Security
Most email systems use the Privacy Enhanced Mail (PEM) or Secure/Multipurpose Internet Mail Extensions (S/MIME), which are file formats used for storing and sending cryptographic keys. To make the exchange of messages as secure as possible, they use digital certificates to verify digital signatures and key exchange to encrypt and decrypt messages.
VPN
Also known as “secure tunnels,” virtual private networks (VPNs) use digital certificates to ensure that communications between secure networks over an unsecured network remains protected.
SET
Secure Electronic Transaction (SET) is a protocol commonly applied in credit card transactions done over an unsecured network. Digital certificates secure communications for merchants, banks, and cardholders, making all transactions indisputable or unforgeable.