asymmetric encryption algorithm uses two completely different but perfectly matched keys-public key and private key. When using asymmetric encryption algorithm to encrypt files, only a pair of matched public keys and private keys can be used to complete the encryption and decryption process of plaintext. Encrypt plaintext with public key, and decrypt ciphertext with private key. Moreover, the sender (encryptor) knows the public key of the receiver, and only the receiver (decryptor) is the only one who knows his private key. The basic principle of asymmetric encryption algorithm is that if the sender wants to send encrypted information that only the receiver can interpret, the sender must first know the public key of the receiver, and then encrypt the original text with the public key of the receiver; After receiving the encrypted ciphertext, the recipient can decrypt the ciphertext only by using his own private key. Obviously, using asymmetric encryption algorithm, before the sender and receiver communicate, the receiver must send the public key that he has randomly generated to the sender, and keep the private key himself. Because asymmetric algorithm has two keys, it is especially suitable for data encryption in distributed systems. The widely used asymmetric encryption algorithms include RSA algorithm and DSA proposed by American National Bureau of Standards. Encryption based on asymmetric encryption algorithm