# <a href="#"><img src="media/BLAKE3.svg" alt="BLAKE3" height=50></a>
BLAKE3 is a cryptographic hash function that is:
- **Much faster** than MD5, SHA-1, SHA-2, SHA-3, and BLAKE2.
- **Secure**, unlike MD5 and SHA-1. And secure against length extension,
unlike SHA-2.
- **Highly parallelizable** across any number of threads and SIMD lanes,
because it's a Merkle tree on the inside.
- Capable of **verified streaming** and **incremental updates**, again
because it's a Merkle tree.
- A **PRF**, **MAC**, **KDF**, and **XOF**, as well as a regular hash.
- **One algorithm with no variants**, which is fast on x86-64 and also
on smaller architectures.
The [chart below](https://github.com/BLAKE3-team/BLAKE3-specs/blob/master/benchmarks/bar_chart.py)
shows BLAKE3's performance on modern server hardware, an Intel Cascade
Lake-SP 8275CL processor:
<p align="center">
<img src="media/speed.svg" alt="performance graph">
</p>
BLAKE3 is based on an optimized instance of the established hash
function [BLAKE2](https://blake2.net) and on the [original Bao tree
mode](https://github.com/oconnor663/bao/blob/master/docs/spec_0.9.1.md).
The specifications and design rationale are available in the [BLAKE3
paper](https://github.com/BLAKE3-team/BLAKE3-specs/blob/master/blake3.pdf).
The default output size is 256 bits. The current version of
[Bao](https://github.com/oconnor663/bao) implements verified streaming
with BLAKE3.
This repository is the official implementation of BLAKE3. It includes:
* The [`blake3`](https://crates.io/crates/blake3) Rust crate, which
includes optimized SIMD implementations, with runtime CPU feature
detection on x86. SSE4.1 and AVX2 are supported in pure Rust. The `c`
feature enables C/assembly implementations and AVX-512 support. The
`c_neon` feature enables ARM NEON support. Multi-threading is also
supported, and the `rayon` feature provides a
[Rayon](https://github.com/rayon-rs/rayon)-based implementation.
* The [`b3sum`](https://crates.io/crates/b3sum) Rust crate, which
provides a command line interface. You can install it from
[crates.io](https://crates.io/crates/b3sum) with `cargo install
b3sum`. It enables the `rayon` and `c` features of the `blake3` crate
by default.
* The [C implementation](c), which like the Rust implementation includes
SIMD code and dynamic CPU feature detection on x86. Unlike the Rust
implementation, it's not currently multi-threaded. The
[README](c/README.md) provides build examples.
* The [reference implementation](reference_impl/reference_impl.rs),
which is discussed in Section 5.1 of the [BLAKE3
paper](https://github.com/BLAKE3-team/BLAKE3-specs/blob/master/blake3.pdf).
This implementation is much smaller and simpler than the optimized
ones above. If you want to see how BLAKE3 works, or you're writing a
port that doesn't need multi-threading or SIMD optimizations, start
here.
* [](https://github.com/BLAKE3-team/BLAKE3/actions)
BLAKE3 was designed by:
* [@oconnor663 ](https://github.com/oconnor663) (Jack O'Connor)
* [@sneves](https://github.com/sneves) (Samuel Neves)
* [@veorq](https://github.com/veorq) (Jean-Philippe Aumasson)
* [@zookozcash](https://github.com/zookozcash) (Zooko)
The development of BLAKE3 was sponsored by
[Teserakt](https://teserakt.io) and [Electric Coin Company](https://electriccoin.co).
*NOTE: 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](https://github.com/P-H-C/phc-winner-argon2).*
## Usage
### The `b3sum` utility
The `b3sum` utility allows you to process files and data from standard
input using BLAKE3 in any of its three modes.
To use `b3sum` on the command line, [install Rust and
Cargo](https://doc.rust-lang.org/cargo/getting-started/installation.html),
and then run:
```bash
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, for example as follows:
```bash
# 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
```
### The `blake3` crate
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:
```rust
// 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:
```rust
// MAC an input 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]"`:
```rust
// 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](CONTRIBUTING.md).
## Intellectual property
The Rust code is copyright Jack O'Connor, 2019-2020.
The C code is copyright Samuel Neves and Jack O'Connor, 2019-2020.
This work is released into the public domain with CC0 1.0.
Alternatively, it is licensed under the Apache License 2.0.