The function of MD5 (full name is message-digest algorithm 5) is to "compress" large-capacity information into a secret format before signing the private key with digital signature software. Its typical application is to generate a message digest for a message to prevent it from being tampered with. Generally speaking, MD5 code is a verification code, just like our personal ID card, everyone's is different. MD5 code is the unique check code for each file (MD5 is case-insensitive, but as there are as many as 128 bits in MD5 code, the possibility that any information has the same MD5 code is very low, which is generally considered impossible), and it is often used for encrypted storage of passwords, digital signature and file integrity verification. Through MD5 verification, you can check the correctness of the file, such as whether the downloaded file is bound with other third-party software or Trojan horses or backdoors (if the verification result is incorrect, it means that the original file has been tampered with without authorization).