The certificate chain is a sequence of certificates linked together using digital signatures, providing a trust hierarchy to verify the authenticity of a digital certificate.
When a user visits a secure website, the user’s browser receives a digital certificate from the website’s server. The browser then checks the digital certificate’s information, such as the domain name, expiration date, and issuer, to confirm that it is valid.
If the certificate was issued by a trusted certificate authority (CA), the browser will already have the root certificate of that CA stored in its certificate store. The browser verifies the digital signature of the certificate by checking the signature against the CA’s public key. If the signature is valid, the browser trusts the certificate and establishes a secure connection with the website.
If the certificate was issued by an intermediate CA, the browser will first check if it has the root certificate of the intermediate CA stored in its certificate store. If not, the browser will retrieve the intermediate CA’s certificate from the server and verify its digital signature using the public key of the next CA in the chain until it reaches the root CA.
This chain of trust ensures that the user’s browser can validate the authenticity of the website’s digital certificate and protect against potential security threats.
