Certificates

The use of public key encryption (asymmetric encryption) allows for the decryption of data encrypted with the corresponding public key by the holder of a private key. However, it doesn’t provide any confirmation of the identity of the person who owns the public key. To establish a link between public keys and specific owners, certificates are utilized with the aid of a trusted third party known as a certificate authority (CA). The CA confirms the identity of the owner using other methods and creates a certificate that the owner can use to verify that the public key belongs to them. By trusting this process, the receiver of a digitally signed message using the public key of the certificate can confirm that the message was sent and signed by the claimed sender. Additionally, the recipient can use the public key to encrypt a response that only the intended receiver can open.

These certificates can be issued by different CAs; imagine if each CA used its own format...