Digital certificate is a series of numbers representing the identity information of all communication parties in Internet communication, and provides a way to verify the identity of communication entities on the Internet. A digital certificate is not a digital ID card, but a seal or stamp affixed by an identity authentication institution (or a signature affixed to a digital ID card). It is issued by the authoritative organization-CA, also known as the Certificate Authority Center, and people can use it to identify each other on the Internet.

Asymmetric encryption algorithm needs two keys: public key and private key. The public key and the private key are a pair. If the data is encrypted with the public key, it can only be decrypted with the corresponding private key. If the data is encrypted with a private key, it can only be decrypted with the corresponding public key. Because encryption and decryption use two different keys, this algorithm is called asymmetric encryption algorithm. The basic process of asymmetric encryption algorithm to realize the exchange of confidential information is: Party A generates a pair of keys and discloses one of them to other parties as a public key; Party B who has obtained the public key uses this key to encrypt confidential information and then sends it to Party A; Party A decrypts the encrypted information with another private key saved by itself.

On the other hand, Party A can use Party B's public key to sign the confidential information before sending it to Party B; Party B will use its own private key to check the data.

Party A can only use its private key to decrypt any information encrypted with its public key. Asymmetric encryption algorithm has good confidentiality and does not require end users to exchange keys.

The characteristics of asymmetric cryptosystem: the strength of the algorithm is complex, and the security depends on the algorithm and key. However, due to the complexity of its algorithm, the encryption and decryption speed is not as fast as that of symmetric encryption and decryption. Symmetric cryptography has only one key, and it is not public. If you want to decrypt it, you must let the other party know the key. Therefore, ensuring its security means ensuring the security of the key, while asymmetric key system has two kinds of keys, one of which is public, so there is no need to transmit the other party's key like symmetric cipher. This makes it safer.