Working

In the process of certificate-based authentication, when a user requests access to a protected resource, the server responds by presenting its certificate to the user’s browser. The browser then verifies the authenticity of the server’s public certificate. Subsequently, an authentication request is sent from the server, prompting the user to authenticate themselves. Concurrently, while the user undergoes authentication, their browser provides the server with the user’s certificate for validation. Upon successful validation of the user’s identity by the server, access to the network or protected resource is granted.

To authenticate users, machines, or devices, certificate-based authentication servers use the certificates and single sign-on (SSO) mechanisms. This authentication process hinges on the interaction of public keys, private keys, and certificate authorities (CAs). By leveraging these cryptographic elements, certificate-based authentication ensures secure and reliable verification of identities, enhancing the overall security of network access and resource utilization.

As, we know that each public key has a corresponding private key, and it is kept secret. When any data is encrypted using the public key, it can only be decrypted with the private key. This configuration enhances the security during authentication since each private key is unique to the individual or device.

Now, to ensure security, certificates should be signed digitally by trusted third-party certificate authorities (CA) who verify the identity. This process takes place between your browser and the server you are communicating with.

User authentication is essential for access management and developing a zero-trust architecture in enterprises. Digital certificates prevents unauthorized individuals from penetrating servers, networks, or applicationsonly such that only legitimate users can access protected resources.

Public Key Infrastructure (PKI) and certificate-based authentication play a key role in this by minimizing dependence on traditional password-based login methods. Once users log into their devices, they’re not typically asked to enter their password again. Instead, their identity is linked to their digital attributes or their device’s identity and verified by the designated server.

Hence, digital certificates play an essential role in Public Key Infrastructure (PKI), acting as digital “ID cards” for users and devices in the digital domain. Similar to traditional identification documents, each digital certificate possesses unique attributes.

These certificates, like the X.509 certificate, contain crucial information such as:

• Public key
• User or device’s name
• Issuing Certificate Authority (CA)
• Validity start and end dates
• Certificate version number
• Serial number

Digital certificates are considered reliable because users and devices must verify their identity before receiving them from a reputable Certificate Authority (CA). This CA serves as a trusted third party, similar to government institutions such as the Department of Motor Vehicles (DMV) or town halls that issue marriage licenses.

The CA thoroughly reviews Certificate Signing Requests (CSR), which are the documents submitted for new digital certificates. It verifies the information against official sources to ensure legitimacy. Only once the CA confirms the claimed identity and validates all details does it issue a client authentication certificate.

There are local and private CAs, and some organizations choose to issue their client authentication certificates instead of relying on widely recognized CAs like IdenTrust or DigiCert. However, private certificates lack the verification process performed by public CAs and are not trusted for securing access to external resources. Instead, they are suitable for internal purposes only.

The process works like this:

• The client starts the connection with the server.
• The server sends its public certificate to the client.
• The client checks the server’s certificate to ensure it’s valid.
• The server requests the client’s certificate.
• The client signs a random number with its private key and sends it, along with its public certificate, back to the server.
• The server verifies that the signed random number was indeed signed by the client using the client’s public certificate.
• Now a server checks the validity of a certificate, it is confirming that the client’s certificate has not expired or been revoked.
• If all necessary checks are successful, the server can use the attributes from the certificate to authenticate the user in its system.

• Sometimes, additional verification steps may required, such as need of verifying the Certificate Authority’s signature and tracing it back to the root CA for added security. Hence, this process guarantees that transmission between the client and server is secure and the identities of both parties are verified before any transactions or data exchanges take place.

Certificate-Based Authentication is a cryptographic technique that enables secure identification of one computer by another across a network connection. It uses a public-key certificate. This authentication system confirms a user’s or device’s identity using digital certificates issued by a trusted authority such as a government agency or web server to verify its authenticity.

The validity of the certificate is verified against a list of trusted certificates. Access to secure resources is granted only if the certificate is on the list. Internet security protocols use certificates for authentication. For example, SSL/TLS is widely used by web browsers for secure online transactions.

Let’s see some examples of how common Certificate-Based Authentication (CBA) is. For example, the smart card is used for accessing offices or other buildings. Another example is the SSL/TLS protocol used in web browsers. CBA is also a key component of any Public Key Infrastructure (PKI) implementation.