Definitions for "Hash function"
An algorithm mapping or translating one sequence of bits into another, generally smaller set (the hash result) such that (1) a message yields the same hash result every time the algorithm is executed using the same message as input, (2) it is computationally infeasible that a message can be derived or reconstituted from the hash result produced by the algorithm, and (3) it is computationally infeasible that two messages can be found that produce the same hash result using the algorithm. An algorithm which calculates a value based on a data object, mapping the data object to a smaller data object, which is the hash result. The value is more often than not a fixed-size value. A very simplistic hash function is a checksum. The kind of hash function necessary for SSL security applications is called a cryptographic hash function.
A hash function is a computation that takes a variable-size input and returns a fixed-size string, which is called the hash value. Compare with message digest.
In cryptography, a hash function or one-way hash function is an algorithm that produces a given value when applied to a given block of data. The result of a hash function can be used to ensure the integrity of a given block of data. For a hash function to be considered secure, it must be very difficult, given a known data block and a known result, to produce another data block that produces the same result.
a cryptographic primitive used for digital signatures and password protection
Keywords:  extract, whole, way, take, short
a way to take a whole document and create a short extract from it
Keywords:  art, encryption, known, form
a form of encryption known in the art