The concept of encryption and decryption and the implementation of DES encryption algorithm

Plaintext: also known as plain text is information that users can directly understand

Cipher text: Cipher text is a collection of meaningless random code

Encryption: Encryption is the process of converting plaintext into ciphertext under the control of a specific algorithm and key.

Decryption: converting ciphertext into plaintext by inputting a secret key under the control of a specific algorithm

encryption algorithm decryption algorithm

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Encryption algorithm is divided into symmetric encryption algorithm (private key algorithm) and asymmetric encryption algorithm (public key algorithm), symmetric encryption algorithm and asymmetric encryption algorithm is the difference between the encryption key and decryption key of symmetric encryption algorithm is the same.

Famous encryption algorithms are DES/3DES, IDEA, RC series, CAST, AES advanced data encryption, etc.

DES encrypts 64-bit ciphertext blocks in block mode, with a fixed 56-bit key. The encryption process is as follows:

Input 64-bit plaintext data----permutation function permutation-----16 rounds of iteration under key control-----swap left and right 32 bits------second permutation with inverse function----output ciphertext data

3DES encryption algorithm is to use three keys respectively DES algorithm implementation three times