What is a hash function?

In cryptography and computer science, a hash function is a mathematical function that maps data of arbitrary size to a fixedsize output, called a hash value or hash. The purpose of a hash function is to take input data and produce a hash value that represents the data in a condensed form. The resulting hash value is a unique representation of the original data, meaning that any change to the input data will result in a different hash value. Hash functions are commonly used in cryptography, data integrity checking, and digital signatures.