[−][src]Crate highway
This crate is a native Rust port of Google's HighwayHash, which is a fast, keyed, and strong hash function that can take advantage of SIMD instructions (SSE 4.1 and AVX 2) for speed ups that allow it to be faster than traditional cryptographic hash functions and even outpace less secure functions at large payloads. HighwayHash allows for an incremental approach to hashing and can output 64bit, 128bit, and 256bit values.
Caution
HighwayHash (the algorithm) has not gone undergone extensive cryptanalysis like SipHash (the default hashing algorithm in Rust), but according to the authors, HighwayHash output bits are uniformly distributed and should withstand differential and rotational attacks. Hence HighwayHash is referred to as a strong hash function, not a cryptographic hash function. I encourage anyone interested to peruse the paper to understand the risks.
Examples
use highway::{HighwayBuilder, HighwayHash, Key}; // HighwayHash requires a key that should be hidden from attackers // to ensure outputs are unpredictable, so attackers can't mount // DoS attacks. let key = Key([1, 2, 3, 4]); // A HighwayBuilder is the recommended approach to hashing, // as it will select the fastest algorithm available let mut hasher = HighwayBuilder::new(&key); // Append some data hasher.append(&[255]); // After all data has been appended, you ask for // 64, 128, or 256bit output. The hasher is consumed // after finalization. let res: u64 = hasher.finalize64(); assert_eq!(0x07858f24d_2d79b2b2, res);
Creating a 128bit and 256bit hash is just as simple.
use highway::{HighwayBuilder, HighwayHash, Key}; // Generate 128bit hash let key = Key([1, 2, 3, 4]); let mut hasher128 = HighwayBuilder::new(&key); hasher128.append(&[255]); let res128: [u64; 2] = hasher128.finalize128(); assert_eq!([0xbb007d2462e77f3c, 0x224508f916b3991f], res128); // Generate 256bit hash let key = Key([1, 2, 3, 4]); let mut hasher256 = HighwayBuilder::new(&key); hasher256.append(&[255]); let res256: [u64; 4] = hasher256.finalize256(); let expected: [u64; 4] = [ 0x7161cadbf7cd70e1, 0xaac4905de62b2f5e, 0x7b02b936933faa7, 0xc8efcfc45b239f8d, ]; assert_eq!(expected, res256);
Use highway hash in standard rust collections
use std::collections::HashMap; use highway::{HighwayBuildHasher, Key}; let mut map = HashMap::with_hasher(HighwayBuildHasher::new(Key([ 0xcbf29ce484222325, 0xc3a5c85c97cb3127, 0xb492b66fbe98f273, 0x9ae16a3b2f90404f, ]))); map.insert(1, 2); assert_eq!(map.get(&1), Some(&2));
Or if utilizing a key is not important, one can use the default
use std::collections::HashMap; use std::hash::BuildHasherDefault; use highway::HighwayHasher; let mut map = HashMap::with_hasher(BuildHasherDefault::<HighwayHasher>::default()); map.insert(1, 2); assert_eq!(map.get(&1), Some(&2));
Use Cases
HighwayHash can be used against untrusted user input where weak hashes can't be used due to exploitation, verified cryptographic hashes are too slow, and a strong hash function meets requirements. Some specific scenarios given by the authors of HighwayHash:
- Use 64bit hashes to for authenticating short lived messages
- Use 128 / 256bit hashes are good for checksums (ie: longer lived data, or strong guarantees against collisions)
Structs
HighwayBuildHasher | |
HighwayBuilder | Main HighwayHash implementation that delegates to one of the other implementations depending on the target compiled for and a runtime CPU check. |
HighwayHasher | |
Key | Key used in HighwayHash that will drastically change the hash outputs. |
PortableHash | Portable HighwayHash implementation. Will run on any platform Rust will run on. |
Traits
HighwayHash | The shared trait between all the hashing implementations, which directs the APIs available for appending data and receiving a hash result. |