unsigned char hash[crypto_shorthash_BYTES]; unsigned char key[crypto_shorthash_KEYBYTES]; crypto_shorthash_keygen(key); crypto_shorthash(hash, SHORT_DATA, SHORT_DATA_LEN, key);
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
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.
- Hash tables
- Probabilistic data structures such as Bloom filters
- Integrity checking in interactive protocols
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
in whose length is
inlen bytes, using the key
crypto_shorthash_KEYBYTES bytes and can be created using
The same message hashed with the same key will always produce the same output.
- The key has to remain secret. This function will not provide any mitigations against DoS attacks if the key is known from attackers.
- When building hash tables, it is recommended to use a prime number for the
table size. This ensures that all bits from the output of the hash function
are being used. Mapping the range of the hash function to
[0..N)can be done efficiently without modulo reduction.
- libsodium >= 1.0.12 also implements a variant of SipHash with the same key
size but a 128-bit output, accessible as