Hashing
A hash function is a mathematical function that converts any digital data into an output string with a fixed number of characters. Hashing is the one-way act of converting the data (called a message) into the output (called the hash). Hashing is useful to ensure the authenticity of a piece of data and that it has not been tampered with since even a small change in the message will create an entirely different hash. Hash functions are the basic tools of modern cryptography that are used I information security to authenticate transactions, messages, and digital signatures.