Hashing functions are used for several applications in computer science, for example, cryptography and document fingerprinting. The main purpose of a hashing function is to map large amounts of input to a fixed length output. In cryptography, hashing is used to ensure that a message or document has not been tampered with. If the document or message is altered in any way (even a single character), the hash value is also altered. It is therefore almost impossible to create a document or message with a given hash value.