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

Clear text: Also known as the user can directly read the information

Redaction: Ciphertext is a collection of meaningless, messy code

Encryption: Encryption is a process of converting plaintext into redact under the control of certain algorithms and keys.

Decryption: Enter a key under the control of a particular algorithm to convert ciphertext into plaintext

Encryption Algorithm Decryption Algorithm

plaintext ----------------- ciphertext ------------------ plaintext

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

The famous encryption algorithms are: Des/3des, Idea, RC series, CAST, AES advanced data encryption, etc.

DES in block mode to encrypt the 64bit cipher block, the key is fixed 56bit, theencryption process is as follows:

input 64bit plaintext data ------ permutation function substitution ------The------ Exchange around the key control 32bit------The second substitution of inverse function -------- output ciphertext data

3DES encryption algorithm is to use 3 keys respectively to the DES algorithm execution 3 times

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