# Hash logic

Keys are hashed. 

## Memcached hashes

Memcached itself uses either:

* [Jenkins hash](https://en.wikipedia.org/wiki/Jenkins_hash_function)
  * http://burtleburtle.net/bob/hash/doobs.html
  * http://burtleburtle.net/bob/c/lookup3.c Public domain.
* [Murmur 3 hash](https://en.wikipedia.org/wiki/MurmurHash)
  * [Murmur 3 in Go](https://github.com/spaolacci/murmur3)
  
## Golang

Beyond the Go ports of these hashes, Go includes native alternatives: 

* Jenkins hash
  * https://github.com/mtchavez/jenkins MIT license.
  * https://github.com/tsaost/bjh port of lookup3.c. BSD license.
  * https://github.com/Apsalar/lookup3 hashlittle() from lookup3.c. Optimized for compatibility/portability,
    not for performance. Implements `hash.Hash32`. Public domain.
  * https://github.com/MstrVLT/lookup3/ port of lookup3.c. License undefined.
* Murmur 3:
  * https://github.com/reusee/mmh3 MIT license.
  * https://github.com/huichen/murmur APL 2.0 license.
  * https://github.com/go-ego/murmur APL 2.0 license. Based on huichen's version.
  * https://github.com/beevik/murmur License undefined.
  * https://github.com/ericx10ng/murmurhash2-go License undefined: was MIT but got removed.
* xxhash:
  * https://github.com/vova616/xxhash/blob/master/xxhash.go (not ARM-compatible). MIT license.
* Golang standard library hashes:
  * hash/adler32
    * https://golang.org/pkg/hash/adler32/
  * hash/crc32
    * https://golang.org/pkg/hash/crc32/
    * The Castagnoli polynomial may be hardware-accelerated on post-Nehalem CPUs compiled with 6g
        (https://stackoverflow.com/questions/23436358/bob-jenkins-hash-getting-bad-performance)
  * hash/crc64:
    * https://golang.org/pkg/hash/crc64/
  * hash/fnv:
    * https://golang.org/pkg/hash/fnv/
* Golang [crypto](https://golang.org/pkg/crypto/#pkg-subdirectories) package includes many 
  cryptographic hashed with optimized implementations too. Most interesting are probably MD5 and SHA1
  * AES (Rijndael), 
  * Cipher package provides bloc cipher modes around low-level ciphers, no specific hashes.
  * DES (DIPS 46-3)
  * DSA (FIPS 186-3)
  * ECDSA (FIPS 186-3)
  * Elliptic package doesn't directly apply
  * HMAC
  * MD5 (RFC 1321)
  * rand package doesn't directly apply
  * RC4, RSA provide encryption, don't directly apply
  * SHA1 (RFC 3174). Reported to be as fast as a Jenkins hash, but may not has optimal distribution
    properties
  * SHA-256, SHA-384, SHA512, SHA512-224, SHA-512/256 (FIPC 180-4)
  * subtle package doesn't directly apply
  * TLS 1.2, doesn't directly apply
  * X.509, doesn't directly apply