Cryptographic hash

Computational thinking, problem-solving and programming

A cryptographic hash function (CHF) is a hash function that is suitable for use in cryptography. It is a mathematical algorithm that maps data of arbitrary size (often called the "message") to a bit string of a fixed size (the "hash value", "hash", or "message digest") and is a one-way function, that is, a function which is practically infeasible to invert. Ideally, the only way to find a message that produces a given hash is to attempt a brute-force search of possible inputs to see if they produce a match, or use a rainbow table of matched hashes. Cryptographic hash functions are a basic tool of modern cryptography.

The ideal cryptographic hash function has the following main properties:

• it is deterministic, meaning that the same message always results in the same hash
• it is quick to compute the hash value for any given message
• it is infeasible to generate a message that yields a given hash value
• it is infeasible to find two different messages with the same hash value
• a small change to a message should change the hash value so extensively that the new hash value appears uncorrelated with the old hash value (avalanche effect)