Cryptographic

BLAKE3

A successor to BLAKE2, released in 2020 by O’Connor, Aumasson, Neves, and Wilcox-O’Hearn. Built around a Merkle-tree of small BLAKE2-style compressions; the result is the fastest secure hash function on modern multi-core CPUs and a clean basis for streaming, parallel, and extendable-output use cases.

At a glance

Three modes in one design

1. Hashing , the default, plain content addressing.
2. Keyed hashing , pass a 32-byte key to get a one-shot MAC, no HMAC needed.
3. Key derivation , derive_key(context, input) uses an ASCII context string to domain-separate keys derived from the same input.

All three modes share the same compression function, distinguished by flag bits inside each node.

Why it is fast

• Tree structure , the input is split into 1024-byte chunks; each chunk and pair of chunks can be processed in parallel.
• SIMD-friendly compression, AVX-512, AVX2, NEON paths in the reference implementation easily reach 5–10 GB/s on commodity desktops.
• Only 7 rounds , far fewer than BLAKE2b (12), SHA-256 (64), or SHA-3 (24), made possible by the more conservative tree structure.
• Streaming or random-access, you can hash a 100 GB file in one streaming pass, or verify a specific 1 MB chunk in O(log n) tree-node hashes given the Merkle proof.

Built-in XOF

BLAKE3 produces unbounded output: after finishing the absorption tree, you can call finalize(N) for any N. The streaming property and the keyed-derivation mode make BLAKE3 a natural fit for KDFs (a replacement for HKDF in some new designs).

Where it is used

• Build systems , Bazel, Buck2, sccache use BLAKE3 for content addressing.
• Backup / sync tools , Restic, Kopia, IPFS optional.
• File transfer protocols , HTTP/3 content integrity drafts.
• Cryptocurrency , selectively; the conservative crypto crowd still leans toward SHA-256 / SHA-3 for asset hashes.

Security

BLAKE3’s round count is aggressive, justified by the tree structure and a margin smaller than SHA-3’s. No collision or preimage attack better than generic is known on full BLAKE3 at the time of writing. For ultra-conservative use, BLAKE2b or SHA-3 retain larger margins.

Try it

The multi-algorithm hasher includes BLAKE3-256. Run the comparatorto see BLAKE3’s throughput against SHA-256 and SHA-3-256.

References

• BLAKE3 specification (PDF)
• BLAKE3 reference implementation (Rust + C)
• Jack O’Connor , BLAKE3: One function, fast everywhere (talk)