Short-input hashing
Example
#define SHORT_DATA ((const unsigned char *) "Sparkling water")
#define SHORT_DATA_LEN 15
unsigned char hash[crypto_shorthash_BYTES];
unsigned char key[crypto_shorthash_KEYBYTES];
randombytes_buf(key, sizeof key);
crypto_shorthash(hash, SHORT_DATA, SHORT_DATA_LEN, key);
Purpose
Many applications and programming language implementations were recently found to be vulnerable to denial-of-service attacks when a hash function with weak security guarantees, such as Murmurhash 3, was used to construct a hash table.
In order to address this, Sodium provides the crypto_shorthash() function,
which outputs short but unpredictable (without knowing the secret key)
values suitable for picking a list in a hash table for a given key.
This function is optimized for short inputs.
The output of this function is only 64 bits. Therefore, it should not be considered collision-resistant.
Use cases:
- Hash tables
- Probabilistic data structures such as Bloom filters
- Integrity checking in interactive protocols
Usage
int crypto_shorthash(unsigned char *out, const unsigned char *in,
unsigned long long inlen, const unsigned char *k);
Compute a fixed-size (crypto_shorthash_BYTES bytes) fingerprint for the message in whose length is inlen bytes, using the key k.
The k is crypto_shorthash_KEYBYTES bytes and can be created using randombytes_buf().
The same message hashed with the same key will always produce the same output.
Constants
crypto_shorthash_BYTEScrypto_shorthash_KEYBYTES
Algorithm details
SipHash-2-4