SLO:
Zgoščevalna funkcija (hash function) je algoritem, ki dobi kot vhod poljubno dolgo sporočilo, kot izhod pa vrne fiksno dolgo binarno vrednost (hash value). Uporabljamo jo za preoblikovanje poljubno dolgih vhodnih sporočil v izhodne vrednosti dolžine 128 bitov.
Pomembnost te funkcije je, da je nepovratna ali enosmerna, to pomeni, da je nemogoče najti vhodno sporočilo, če poznamo izhodno vrednost. Prav tako je nemogoče najdi dve vhodni sporočili, ki bi ob izhodu tvorili enaka rezultata.
Najpogostejši algoritmi so: MD4, MD5, SHA-1, SHA-2, SHA-3, ... itd.
EN:
A hash function is any function that can be used to map data of arbitrary size to fixed-size values. The values returned by a hash function are called hash values, hash codes, digests, or simply hashes. The values are usually used to index a fixed-size table called a hash table. Use of a hash function to index a hash table is called hashing or scatter storage addressing.
Hash functions and their associated hash tables are used in data storage and retrieval applications to access data in a small and nearly constant time per retrieval. They require an amount of storage space only fractionally greater than the total space required for the data or records themselves. Hashing is a computationally and storage space-efficient form of data access that avoids the non-constant access time of ordered and unordered lists and structured trees, and the often exponential storage requirements of direct access of state spaces of large or variable-length keys.
The most common hash algorithms are: MD4, MD5, SHA-1, SHA-2, SHA-3, ... itd.