Cryptography includes the following aspects: 1. Cryptography: mainly studies the method of transforming information in the process of channel to protect information from being stolen, deciphered and used by opponents.

2. Password analysis: mainly study how to analyze and decipher passwords, also known as password attacks.

In addition, cryptography has two important application directions: encrypted communication, whose main task is to ensure that information will not be tampered with and eavesdropped during transmission. Digital signature can be used to verify the identity of the signer and prevent it from being denied.