Message authentication refers to the process of confirming the integrity of messages received on the network. Usually, a hash function (such as MD5 or SHA- 1) is used to verify the integrity and authenticity of the text. Digital signature is to use a public key system (such as RSA) to generate a pair of public key and private key, use the private key to sign the message, and use the public key to verify the file signature, which plays a role in ensuring the undeniable file.