Authentication is the process of establishing that you are who you claim to be: that you are authentically you. Certificate-based authentication is the process of establishing your identity using electronic documents known as digital certificates.
A digital certificate is like an electronic passport used to prove your identity by confirming your ownership of a private key. Digital certificates contain:
Public key information
A digital signature derived from the private key of the certificate authority (CA) verified with their public key
For certificate-based authentication to work properly, the user must have a private key with information that corresponds to the public key in a certificate. The private key is unique to the user and uses the process of public key cryptography to verify a user’s identity so that the user can access protected network resources. A public key is validated through its relationship with the private key, and if it was signed by a trusted authority.
Note: The private key of the user should never leave the user's possession.
How certificate-based authentication works
Certificate-based authentication servers use certificates and single sign-on (SSO) to authenticate a user, machine, or device. Authentication is performed through the interaction of public keys, private keys, and certificate authorities (CAs).
Each public key comes paired with a unique private key. Although public keys are published, the corresponding private key is kept secret. Data that’s encrypted with the public key can be decrypted only with the corresponding private key. Because each private key is unique to the individual or device, this ensures greater security during the authentication process.
To prevent malicious actors from masquerading as you, certificates must be digitally signed by a third party (the CA) who vouches for your authenticity. The entire authentication process is performed in your browser and the server you are interacting with.
The process is generally as follows:
A user makes a request to access a protected resource.
The server presents its certificate to the browser, and the browser validates the public certificate.
An authentication request is made from the server for the user to authenticate themselves.
While the user is being authenticated, the browser presents the user’s certificate to the server for validation.
The server authenticates the user’s identity and allows access to the network.
Why use certificate-based authentication?
There are many benefits to using certificate-based authentication:
Increased security. Traditional username and password combinations are among the least secure forms of authentication. Often, these passwords are easy to guess and are stored in an insecure manner, such as written down on sticky notes. Certificate-based authentication is a much stronger form of authentication and eliminates vulnerable passwords. Eliminating passwords also decreases the possibility of phishing or brute force attacks from bad actors.
Streamline authentication. Certificates allow users to be authenticated without having to remember several username and password combinations. Users often spend considerable time guessing and resetting passwords when they have many to remember. Certificate-based authentication decreases friction for the end user while increasing employee productivity.
Ease of deployment. Unlike other authentication methods like one-time passcode (OTP) tokens or biometrics, certificates are stored on the device locally and are implemented without needing any extra hardware. Certificate-based authentication also makes access control very simple. Most solutions come with a cloud management platform that allows administrators to easily issue certificates to new hires, renew certificates, and revoke certificates when no longer needed.