Classification of cryptographic systems

Cryptographic systems can be roughly divided into three categories:

(1) "conventional password", also known as "single key password" and "symmetric password".

(2) "public key cryptography", also known as "double key cryptography" and "asymmetric cryptography".

(3) Identity-based password.

Double-key cryptosystem is a new cryptosystem proposed by W.Diffie and M.E.Heilinan in 1976. Because the encryption and decryption of the double-key cryptosystem are different, and the encryption key can be made public, but only the decryption key needs to be kept secret, so there is no key management problem in the double-key cryptosystem. Another advantage of double-key encryption is that it can have new functions, such as digital signature. The most famous double-key cryptosystem is the RSA cryptosystem proposed by Rivest, Shamir and Ad 1eman in 1977. The disadvantage of double-key cryptography is that the algorithm of double-key cryptography is generally complicated and the encryption and decryption speed is slow.

Therefore, the mixed encryption system of double-key and single-key cipher is widely used in network encryption, that is, single-key cipher is used for encryption and decryption, and double-key cipher 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.