If the key system is based on the key, the cryptographic system can be divided into a single-key cryptography (also called a symmetric cryptography or a private key cryptography) system and a dual-key cryptography (also called an asymmetric cryptography or a private key cryptography) system. public key cryptography) system. Oh, by the way, the so-called key can almost be understood as a password.

In the single-key system, the encryption key and decryption key are the same, or substantially equivalent. In this case, the key is transmitted from the sender through a secure key channel. Receiver.

The characteristic of single-key cryptography is that the same key is used for both encryption and decryption. Therefore, the security of this cryptosystem is the security of the key. If the key is compromised, the cryptosystem is broken. The most influential single-key cipher is the DES algorithm promulgated by the American National Bureau of Standards in 1977. The advantage of single-key password is: high security. Encryption and decryption are fast. The disadvantages are: 1) As the network scale expands, key management becomes a difficulty; 2) The problem of message confirmation cannot be solved; 3) It lacks the ability to automatically detect key leaks.

In the dual-key system, the encryption key and the decryption key are different. At this time, there is no need for a secure channel to transmit the key, but only the local key generator is used to generate the decryption key. Just click the key. Dual-key cryptography is a new cryptography system proposed by W.Diffie and M.E.Heilinan in 1976. Since the encryption and decryption of the dual-key cryptography system are different and the encryption key can be disclosed while only the decryption key needs to be kept secret, there is no key management problem in the dual-key cryptography. Another advantage of dual-key cryptography is that it can have new functions such as digital signatures. The most famous dual-key cryptosystem is the RSA cryptosystem proposed by Rivest, Shamir and Ademan in 1977. The disadvantages of dual-key cryptography

are: the dual-key cryptography algorithm is generally complex and the encryption and decryption speed is slow.

Therefore, encryption in the network generally uses a hybrid encryption system that combines dual-key and single-key cryptography, that is, single-key cryptography is used for encryption and decryption, and dual-key cryptography is used for key transmission. This not only solves the difficulty of key management, but also solves the problem of encryption and decryption speed. At present, it seems that this method can only be like this.