What is a hash value?
Values returned by a so called hash function are called hash values (or also hash codes, digests or simply hashes). A hash function is any kind of function that can be used to map data of arbitrary size into data that has a fixed size. So called hash tables are used in computer programs for a fast data lookup. They accelerate the table and database lookups by detecting duplicated records in large files. Hash functions are also very useful in cryptography, since they allow to easily verify that some input data maps to a given hash value while protecting the original input, for example a plain text password that should stay secret.