For many years, network information security has always been an important research direction in data communication field. In fact, there is a huge possibility that data will be stolen or damaged in the process of network transmission because of the insecurity of TCP/IP protocol. In this situation, information encryption becomes an effective method to ensure communication security. Now, we will talk about cipher system, which makes information encryption possible.
Introduction to cipher system
Cipher system refers to a system which is able to completely solve the problems related to communication security, including confidentiality, data integrity, authentication, identification, controllability and non-repudiation. Actually, cipher system is used to complete the algorithms of encryption and decryption. In general, the encryption process and decryption process of data are both controlled by cipher system and password. Security of cipher system relies on that of password. In modern cryptography, people always pursue encryption algorithm’s integrity, instead of confidentiality.
Classification of cipher system
At present, there are two cipher systems which have been used widely to ensure communication security: private-key cryptosystem and public-key cryptosystem.
- Private-key cryptosystem: private-key cryptosystem is also called single-key cryptosystem or symmetric cryptosystem because its encryption key and decryption key are the same. Both parties involved in communication must appoint a key for their communication through a safe way in order to ensure communication security.
- Public-key cryptosystem: another name of public-key cryptosystem is asymmetric cryptosystem. In this system, the encryption key (Ke) and decryption key (Kd) are different. Therefore, the openness of encryption key has no relation to the security of decryption key. RSA and Elliptic Curve are two common public-key cryptosystems.
Therefore, in private-key cryptosystem, the protection of encryption key has the same importance with that of decryption key. The security of encryption key and decryption key will have a direct impact on the whole system. DES and IDEA are two typical encryption algorithms of private-key cryptosystem.
Communicating through the public-key cryptosystem, users are required to save a lot of public keys (similar to address book). This is actually a big burden for users. At present, Key Distribution Center (KDC) is recognized as an effective solution to managing and distributing public keys. Users only need to save their own private key and the public key of Key Distribution Center in the communication process. In this way, users can also obtain the public key of other users through Key Distribution Center.
In practice, public key is always used in combination with private key. The public key is responsible for sending encryption keys while the private key is responsible for sending encrypted information. However, no matter what kind of cipher system (private-key cryptosystem, public-key cryptosystem or the combination of them) users have adopted, it is necessary for them to save keys safely.