Six encryption algorithms-MD5 Algorithm

The full name of MD5 is "message-Digest algorithm 5" (Information-Abstract AlgorithmIt was developed by the MIT computer science lab and RSA Data Security Inc in Early 1990s and gradually evolved from md2, md3, and md4. Its main function is to compress large-capacity information into a confidential format before signing a private "key" using digital signature software (that is, to convert a string of any length into a long value ). integer ). For example, if anyone on the Earth has their own unique fingerprints, this is the most trustworthy basis for the public security department to identify an individual. Likewise, the MD5 algorithm can generate a unique "digital fingerprint" for any file regardless of its size and format. If someone modifies the file, even if the modification is very small, its MD5 value (that is, the corresponding "digital fingerprint") will change.

The MD5 algorithm uses 128-bit encryption. Even if a computer can try 1 billion lines of plain text per second, it will take 1022 to decrypt the original plain text. The Application of MD5 is very extensive, in 802.1x authentication, EAP-MD5 authentication uses MD5 algorithm, user password is not transmitted in plaintext on the Internet, thus ensuring the security of authentication information. At the same time, it is also applied to encryption and decryption technology. For example, in Unix systems, users' passwords are encrypted using MD5 algorithms (or other similar algorithms) and stored in the file system. When a user logs on, the system calculates the password entered by the user into an MD5 value, and then compares it with the MD5 value saved in the file system to determine whether the entered password is correct. In this step, the system can determine the validity of user logon without knowing the user's plaintext password. In this way, the passwords of common users are not only prevented by the system administrator, but also increase the difficulty of password cracking to some extent. In addition, the familiar Instant Messaging Software myim also uses the MD5 algorithm. The MD5 algorithm is used for file verification. It is widely used in software download sites, Forum databases, and system file security.