HTTPS encryption communication principle and digital certificate system

HTTPS Encrypted Communication principle:

The public key is paired, the public key is publicly available, and the private key is known.

The information encrypted with the public key can only be decrypted by the private key corresponding to it.

A to B to send data, a first with the public key of B to encrypt this piece of data, and then use their private key to the data (digital fingerprint, through the hash function generated) RSA operation to form a signature. b After receiving the data, first use their own private key to decrypt the data, and a public key to a signature verification (to solve the digital fingerprint, and the data received by the digital fingerprint contrast). This ensures that the sender cannot deny that the message has been sent, and that the message will not be tampered with during transmission.

CA Certificate:

A CA certificate is a certificate issued to a user by a CA that contains user information, a user's public key, and a CA's signature.

Online Public users trust the CA (Visa authority) and also know the CA public key (download the CA's own certificate, which contains the CA information and CA public key).

When a user wants a CA certificate, they apply to the CA. After the CA has identified the applicant, he assigns a public private key pair, binds the public key with the applicant's identity, and signs it with the CA private key, and forms a certificate to the applicant. The applicant keeps the private key on its own and is not disclosed.

The CA certificate is actually a CA-issued authentication of the user's public key.

The user receives a certificate, wants to confirm is not the CA certificate, uses the CA public key to verify the certificate's signature, validates passes, thinks that the certificate is the CA certificate, the user information and the user public key in the certificate is CA attestation, is credible.

Root certificate:

The CA's own certificate, which contains the CA's own public key. A signature that is authenticated with this public key is trusted by the user who trusts the certificate and trusts the public key in it.

This certificate is the root of the chain of trust and is self-proving.

HTTPS encryption communication principle and digital certificate system