All I Know About Certificates – Certificate Authority

The article discusses the importance of certificates in the TLS handshake, emphasizing their role in verifying the identity of websites to clients. Certificates are essential for preventing impersonation, as demonstrated through a hypothetical scenario involving a hacker who could misuse a certificate to pose as a legitimate bank. The article clarifies that while anyone can issue certificates, only those from trusted Certificate Authorities (CAs) are reliable. CAs have three main responsibilities: verifying the identity of applicants, safeguarding their private keys, and maintaining client trust. The verification process involves ensuring that the applicant controls the domain for which they seek a certificate, often through methods like the ACME Challenge.

CAs must protect their private keys to prevent unauthorized certificate issuance, as a leak could lead to widespread fraud. To manage this, CAs typically issue intermediate certificates rather than directly issuing to websites, creating a trust chain. The article explains the certificate issuance process, which involves signing a certificate with a private key and the client verifying it with the corresponding public key. Trust in CAs is crucial, as clients store trusted CAs locally. The emergence of Let’s Encrypt is highlighted as a significant development in providing free certificates, leveraging trust from established CAs. The article sets the stage for further exploration of the client's role in the certificate verification process.