Since the 1970s, some scholars have proposed the public key system, which applies the mathematical principle of one-way functions in order to realize the separation of encryption and decryption keys. The encryption key is public and the decryption key is secret. This new cryptographic system has attracted extensive attention and discussion in the cryptographic community Unlike ordinary symmetric cryptography, which uses the same key to encrypt and decrypt data, asymmetric key cryptography uses a pair of matching keys for encryption and decryption, with two keys, one public and one private, which have the following properties: each key performs a one-way processing of the data, and the function of each one is exactly the same as that of the other one. When one is used for encryption, the other is used for decryption. A file encrypted with a public key can only be decrypted with a private key, while a file encrypted with a private key can only be decrypted with a public key. A public *** key is made public by its owner, while a private key must be kept secret. To send a confidential message, the sender must use . Symmetric key encryption, also known as private key encryption, means that the sender and receiver of a message

Use a single key to encrypt and decrypt data. Its biggest advantage is fast encryption/decryption speed,

suitable for encrypting large amount of data, but the key management is difficult.

Asymmetric key encryption system, also known as public key encryption. It requires the use of a pair of keys

to complete the encryption and decryption operations separately, one publicly released, i.e., the public key, and the other

stored secretly by the user himself, i.e., the private key. The sender of a message uses the public key to

encrypt it, while the receiver of the message uses the private key to decrypt it. The public key mechanism is flexible, but encryption and decryption are much slower than with symmetric key encryption.