Hash Functions: How Do Hash Functions Generate Hash Values? A Must-Know for Beginners

A hash function is a "translator" that converts input of arbitrary length into a fixed-length hash value, which serves as the "ID number" of the data. Its core characteristics include: fixed length (e.g., MD5 produces 32 hexadecimal characters), one-way irreversibility (original data cannot be derived from the hash value), near-uniqueness (extremely low collision probability), and the avalanche effect (minor input changes lead to drastic hash value changes). The generation process consists of three steps: input preprocessing into binary, segmented mathematical operations, and merging the results. Unlike encryption functions, hash functions are one-way and do not require a key, while encryption is reversible and requires a key. They have extensive applications: file verification (comparing hash values to prevent tampering), password storage (storing hash values for security), data indexing, and data distribution in distributed systems. As a data fingerprint, the key characteristics of hash functions make them indispensable in security and verification.