cryptographic hash function
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special class of hash function that has certain properties which make it suitable for use in cryptography
~38 min read
Encyclopedic overview
A cryptographic hash function (specifically SHA-1) at work. A small change in the input (in the word "over") drastically changes the output (digest). This is called the avalanche effect.
Hashing is a one-directional mathematical operation which is quick to calculate, yet hard to reverse. So password storage and digital signatures benefit from hashes. Even a small change in the input results in a very different hash. So it is useful to check if two copies of data or software match. Typically the operation works on a block of input data; the hash output is then hashed with the next block, creating a new hash reflecting everything to that point; again and again until the final hash reflects everything through the final block.
Excerpted from Wikipedia’s “cryptographic hash function” article, available under the CC BY-SA 4.0 licence.