At present, encryption and decryption can be mainly divided into the following two categories:
Symmetric key encryption: such as DES algorithm, 3DES algorithm, TDEA algorithm, Blowfish algorithm, RC5 algorithm, IDEA algorithm, etc. Its main feature is that both the encryptor and the decryptor have the same password, and the encryptor and the decryptor can use the key to encrypt and decrypt at will.
Asymmetric password encryption: In this encryption method, the encryptor only has the encryption key, and the encrypted ciphertext cannot be decrypted reversely, while the decryptor only has the decryption key, and the plaintext cannot be encrypted.
There are also some summarization algorithms, such as MD5 and HASH, which are irreversible, but they are often used as confirmation fields or to sign some important matching information to prevent the plaintext content from being modified.