Message Digest Algorithm MD5 (Chinese name is Message Digest Algorithm 5th Edition) is a widely used hash function in computer security field, which is used to protect the integrity of messages. The file number of this algorithm is RFC1321(R. Riverst, Computer Science Laboratory of MIT and RSA Data Security Company, April 1992).

MD5, namely message digest algorithm 5, is used to ensure the integrity and consistency of information transmission. It is one of the widely used hash algorithms in computers (also translated as digest algorithm and hash algorithm), and MD5 has been widely used in mainstream programming languages.

Calculating data (such as Chinese characters) into another fixed-length value is the basic principle of hash algorithm. The predecessor of MD5 is MD2, MD3 and MD4.

The function of MD5 is to "compress" a large amount of information into a secure format before signing the private key with digital signature software (that is, to convert a byte string with any length into a hexadecimal digit string with a certain length).

Besides MD5, sha- 1, RIPEMD and Harvard are also famous.