[][src]Crate highway

This crate is a native Rust port of Google's HighwayHash, which is a fast, keyed, and strong hash function.


HighwayHash (the algorithm) has not 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.


The quickest way to get started:

use highway::{HighwayHasher, HighwayHash};
let res: u64 = HighwayHasher::default().hash64(&[]);
let res2: [u64; 2] = HighwayHasher::default().hash128(&[]);
let res3: [u64; 4] = HighwayHasher::default().hash256(&[]);

A more complete tour of the API follows:

use highway::{HighwayHasher, 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 HighwayHasher is the recommended approach to hashing,
// as it will select the fastest algorithm available
let mut hasher = HighwayHasher::new(key);

// Append some data

// 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::{HighwayHasher, HighwayHash, Key};

// Generate 128bit hash
let key = Key([1, 2, 3, 4]);
let mut hasher128 = HighwayHasher::new(key);
let res128: [u64; 2] = hasher128.finalize128();
assert_eq!([0xbb007d2462e77f3c, 0x224508f916b3991f], res128);

// Generate 256bit hash
let key = Key([1, 2, 3, 4]);
let mut hasher256 = HighwayHasher::new(key);
let res256: [u64; 4] = hasher256.finalize256();
let expected: [u64; 4] = [
assert_eq!(expected, res256);

Use highway hash in standard rust collections

use std::collections::HashMap;
use highway::{HighwayBuildHasher, Key};
let mut map =

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 =

map.insert(1, 2);
assert_eq!(map.get(&1), Some(&2));

Hashing a file, or anything implementing Read

use std::fs::File;
use std::hash::Hasher;
use highway::{PortableHash, HighwayHash};

let mut file = File::open("./README.md").unwrap();
let mut hasher = PortableHash::default();
std::io::copy(&mut file, &mut hasher).unwrap();
let hash64 = hasher.finish(); // core Hasher API
let hash256 = hasher.finalize256(); // HighwayHash API

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 256bit hashes for checksums. Think file storage (S3) or any longer lived data where there is a need for strong guarantees against collisions.

Highwayhash may not be a good fit if the payloads trend small (< 100 bytes) and speed is up of the utmost importance, as Highwayhash hits its stride at larger payloads.

Crate Features

highway is no_std compatible when the default features are disabled. Be aware that the no_std version is unable to detect CPU features and so will always default to the portable implementation. If building for a known SSE 4.1 or AVX 2 machine (and the majority of machines in the last decade will support SSE 4.1), these hashers can still be constructed with force_new.



AVX empowered implementation that will only work on x86_64 with avx2 enabled at the CPU level.


Constructs a hasher used in rust collections


HighwayHash implementation that selects best hash implementation at runtime.


Key used in HighwayHash that will drastically change the hash outputs.


Portable HighwayHash implementation. Will run on any platform Rust will run on.


SSE empowered implementation that will only work on x86_64 with sse 4.1 enabled at the CPU level.



The common set of methods for hashing data.

Type Definitions


HighwayHash implementation that selects best hash implementation at runtime.