MD5 encryption is an irreversible encryption algorithm. The characteristic of the irreversible encryption algorithm is that no key is needed in the encryption process. After the plaintext is input, the system directly processes it into ciphertext through the encryption algorithm. The encrypted data cannot be decrypted. Only the plaintext is re input and processed by the same irreversible encryption algorithm again,Only after the same encrypted ciphertext is obtained and re recognized by the system can it be truly decrypted.