Traditional encryption systems are based on keys.

1. Symmetric key: Symmetric key is also called private key. Encryption and decryption use the same key, and the confidentiality of the key plays a decisive role in the security of the system. Symmetric encryption algorithm has the advantages of fast calculation speed and high encryption and decryption efficiency, but it is difficult to manage and distribute keys and ensure the security of keys.

2. Asymmetric key: Asymmetric key is also called public key. Encryption and decryption use different keys. The public key can be made public, but the private key must be kept secret. The advantages of asymmetric encryption algorithm are higher key security and convenient key management and distribution, but the encryption and decryption speed is slow and the calculation efficiency is low.