Non-cryptographic hash function


The non-cryptographic hash functions are hash functions intended for applications that do not need the rigorous security requirements of the cryptographic hash functions and therefore can be faster and less resource-intensive. Typical examples of CPU-optimized non-cryptographic hashes include FNV-1a and Murmur3. Some non-cryptographic hash functions are used in cryptographic applications ; in this case they are described as universal hash functions.

Applications and requirements

Among the typical uses of non-cryptographic hash functions are bloom filters, hash tables, and count sketches. These applications require, in addition to speed, uniform distribution and avalanche properties. Collision resistance is an additional feature that can be useful against hash flooding attacks; simple NCHFs, like the cyclic redundancy check, have essentially no collision resistance and thus cannot be used with an input open to manipulation by an attacker.
NCHFs are used in diverse systems: lexical analyzers, compilers, databases, communication networks, video games, DNS servers, filesystems—anywhere in computing where there is a need to find the information very quickly.
Estébanez et al. list the "most important" NCHFs:
Non-cryptographic hash functions optimized for software frequently involve the multiplication operation. Since in-hardware multiplication is resource-intensive and frequency-limiting, ASIC-friendlier designs had been proposed, including SipHash, NSGAhash, and XORhash. Although technically lightweight cryptography can be used for the same applications, the latency of its algorithms is usually too high due to a large number of rounds. Sateesan et al. propose using the reduced-round versions of lightweight hashes and ciphers as non-cryptographic hash functions.
Many NCHFs have a relatively small result size : large result size does not increase the performance of the target applications, but slows down the calculation, as more bits need to be generated.