BLAKE2.

BLAKE2 is a cryptographic hash family designed by Jean-Philippe Aumasson, Samuel Neves, Zooko Wilcox-O'Hearn and Christian Winnerlein in 2012 as a streamlined refinement of BLAKE, a SHA-3 finalist. It was standardised in RFC 7693 (2015). Two main variants exist: BLAKE2b (up to 64-byte digests, tuned for 64-bit CPUs) and BLAKE2s (up to 32-byte digests for 32-bit and embedded platforms), each with parallel forms (BLAKE2bp/BLAKE2sp).

How it works

BLAKE2 uses the HAIFA iteration mode over a compression function derived from the ChaCha stream-cipher permutation (G-function mixing with rotations). Crucially it builds keyed hashing, salting, personalisation and tree hashing directly into the primitive, so a keyed BLAKE2 acts as a MAC without a separate HMAC wrapper, avoiding SHA-2's length-extension weakness. Compared with its predecessor it drops the number of rounds (12 for 2b, 10 for 2s) and simplifies padding for speed.

flowchart LR
  M[Message blocks] --> C[Compression f: HAIFA + ChaCha permutation]
  K[Optional key] --> C
  S[Salt / personalization] --> C
  T[Block counter t] --> C
  C --> C2[Chained state h]
  C2 -->|final block flag| O[Digest up to 64 bytes]

Adoption and successors

BLAKE2 is unbroken with no practical collision or preimage attacks, and is faster than MD5, SHA-1, SHA-2 and SHA-3 in software. It underpins the Argon2 password-hashing winner (as its internal compression primitive), WireGuard handshake hashing (BLAKE2s), libsodium's crypto_generichash, and Zcash. The same team released BLAKE3 in 2020, a Merkle-tree design offering further parallelism, though BLAKE2 remains the RFC-standardised, widely-deployed choice.