BLAKE3/README.md

BLAKE3

BLAKE3 is a cryptographic hash function that is:

1. Faster than MD5, SHA1, SHA2, SHA3, and even BLAKE2.
2. Highly parallelizable: The more data and the more cores, the faster it goes. (For you specialists reading this: this is because it is actually a Merkle tree under the hood.)
3. Capable of verified streaming and incremental updates. (Again: the magic of Merkle trees.)
4. Supporting simple hashing as well as PRF, MAC, KDF, XOF
5. Carefully engineered to be simple and safe to use, with no "flavors" or variants.

BLAKE3 is based on an optimized instance of the established hash function BLAKE2, and on the Bao tree mode. The BLAKE3 specifications and design rationale are available in the BLAKE3 paper.

This repository provides the official Rust implementation of BLAKE3, the blake3 crate. It includes optimized SIMD implementations, using dynamic CPU feature detection on x86. SSE4.1 and AVX2 support are implemented in Rust, while AVX-512 and ARM NEON support are implemented in C and controlled by the c_avx512 and c_neon features. Multi-threading is implemented with Rayon and controlled by the rayon feature. This repository also hosts the simplified reference implementation, which is portable and no_std-compatible.

The b3sum sub-crate provides a command line interface. You can install it with cargo install b3sum. It includes multi-threading and AVX-512 support by default.

BLAKE3 was designed by:

• @oconnor663 (Jack O'Connor)
• @sneves (Samuel Neves)
• @veorq (Jean-Philippe Aumasson)
• @zookozcash (Zooko)

The development of BLAKE3 was sponsored by Teserakt and Electric Coin Company.

WARNING: BLAKE3 is not a password hashing algorithm, because it's designed to be fast, whereas password hashing should not be fast. If you hash passwords to store the hashes or if you derive keys from passwords, we recommend Argon2.

Usage

This repo provides the blake3 Rust crate and the b3sum command line tool. To use b3sum on the command line, install Rust and Cargo, and then run:

cargo install b3sum

If rustup didn't configure your PATH for you, you might need to go looking for the installed binary in e.g. ~/.cargo/bin. You can test out how fast BLAKE3 is on your machine by creating a big file and hashing it:

# Create a 1 GB file.
head -c 1000000000 /dev/zero > /tmp/bigfile
# Hash it with SHA-256.
time openssl sha256 /tmp/bigfile
# Hash it with BLAKE3.
time b3sum /tmp/bigfile

To use BLAKE3 from Rust code, add a dependency on the blake3 crate to your Cargo.toml. Here's an example of hashing some input bytes:

// Hash an input all at once.
let hash1 = blake3::hash(b"foobarbaz");

// Hash an input incrementally.
let mut hasher = blake3::Hasher::new();
hasher.update(b"foo");
hasher.update(b"bar");
hasher.update(b"baz");
let hash2 = hasher.finalize();
assert_eq!(hash1, hash2);

// Extended output. OutputReader also implements Read and Seek.
let mut output = [0; 1000];
let mut output_reader = hasher.finalize_xof();
output_reader.fill(&mut output);
assert_eq!(&output[..32], hash1.as_bytes());

Besides hash, BLAKE3 provides two other modes, keyed_hash and derive_key. The keyed_hash mode takes a 256-bit key:

// MAC an output all at once.
let example_key = [42u8; 32];
let mac1 = blake3::keyed_hash(&example_key, b"example input");

// MAC incrementally.
let mut hasher = blake3::Hasher::new_keyed(&example_key);
hasher.update(b"example input");
let mac2 = hasher.finalize();
assert_eq!(mac1, mac2);

The derive_key mode takes a context string of any length and key material of any length, and it outputs a derived key of any length. The context string should be hardcoded, globally unique, and application-specific. A good default format for the context string is "[application] [commit timestamp] [purpose]":

// Derive a couple of subkeys for different purposes.
const EMAIL_CONTEXT: &str = "BLAKE3 example 2020-01-07 17:10:44 email key";
const API_CONTEXT: &str = "BLAKE3 example 2020-01-07 17:11:21 API key";
let input_key = b"some very secret key material (>'-')> <('-'<) ^('-')^";
let mut email_key = [0; 32];
blake3::derive_key(EMAIL_CONTEXT, input_key, &mut email_key);
let mut api_key = [0; 32];
blake3::derive_key(API_CONTEXT, input_key, &mut api_key);
assert!(email_key != api_key);

Contributing

Please see CONTRIBUTING.md

Intellectual property

The source code in the present repository is dual-licensed under CC0 1.0 and Apache 2.0 licences.

The Rust code is copyright Jack O'Connor, 2019. The C code is copyright Samuel Neves and Jack O'Connor, 2019.