What is the most representative of symmetric encryption algorithms?

The most representative of the symmetric encryption algorithms is: DES encryption algorithm; DES encryption uses a block encryption method, using a 56-bit key to encrypt 64-bit plaintext, and finally generates 64-bit ciphertext; algorithm characteristics: The grouping is relatively short, the key is too short, the password life cycle is short, and the operation speed is slow.

#The operating environment of this article: Windows 7 system, Dell G3 computer.

The most classic and representative algorithm among symmetric encryption algorithms is the DES encryption algorithm.

DES algorithm is a symmetric cryptography system in cryptography, also known as the American Data Encryption Standard. It is a symmetric cryptography encryption algorithm developed by IBM in the United States in 1972. The plaintext is grouped by 64 bits, and the key is 64 bits long. The key is actually 56 bits participating in the DES operation (the 8th, 16th, 24th, 32nd, 40th, 48th, 56th, and 64th bits are check bits, making each password The keys have an odd number. 1) The encryption method of grouping the plaintext group and the 56-bit key to form a ciphertext group by bitwise substitution or exchange.

Basic principle:

There are three entry parameters: key, data, mode. key is the key used for encryption and decryption, data is the data for encryption and decryption, and mode is its working mode. When the mode is encryption mode, the plaintext is grouped according to 64 bits to form a plaintext group, and the key is used to encrypt the data. When the mode is decryption mode, the key is used to decrypt the data. In actual application, the key only uses 56 bits out of 64 bits, so that it has high security.

DES features:

The DES algorithm has extremely high security. In addition to using the exhaustive search method to attack the DES algorithm, no more effective method has been found. The exhaustive space of a 56-bit key is 2^56, which means that if a computer is capable of detecting one million keys per second, it will take nearly 2285 years to search for all keys. time, it can be seen that this is difficult to achieve. However, this does not mean that DES is unbreakable. In fact, with the development of hardware technology and the Internet, the possibility of cracking is becoming more and more likely, and the time required is getting less and less. Parallel processing takes hours using specially designed hardware.

In order to overcome the shortcoming of the small key space of DES, people have proposed a variant of triple DES.

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