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BLAKE2 hashing

local blake2 = require'blake2'

A ffi binding of the BLAKE2 fast cryptographic hash.

API

In the table below, ? is either s, b, sp or bp for each variant of the BLAKE2 algorithm.

blake2.blake2?(s, [size], [key], [#out]) -> s \ compute the hash of a string or a cdata buffer. blake2.blake2?(cdata, size, [key]) -> s

blake2.blake2?_digest([key, [#out] | opt_t]) -> digest \ get an object/function that can consume multiple data chunks before returning the hash

digest[:update](s, [size]) \ consume a data chunk digest[:update](cdata, size)

digest[:final]() -> s finalize and get the hash digest:final_to_buffer(buf) finalize and write the hash to a buffer digest:length() -> n hash byte length

digest:reset() prepare for another digestion

The hash is returned raw in a Lua string. To get it as hex use [glue].tohex().

The optional key arg is for keyed hashing (up to 64 bytes for BLAKE2b, up to 32 bytes for BLAKE2s).

The optional #out arg is for reducing the length of the output hash.

The constructors blake2s_digest and blake2b_digest can take a table in place of the key arg in which more options can be specified:

  • salt (''): salt for randomized hashing (up to 16 bytes for BLAKE2b, up to 8 bytes for BLAKE2s).
  • personal (''): personalization string (up to 16 bytes for BLAKE2b, up to 8 bytes for BLAKE2s).
  • fanout (1): fanout (0 to 255, 0 if unlimited, 1 in sequential mode).
  • depth (1): maximal depth of tree (1 to 255, 255 if unlimited, 1 in sequential mode).
  • leaf_length (0): maximal byte length of leaf (0 to 2^32-1, 0 if unlimited or in sequential mode).
  • node_offset (0): node offset (0 to 2^64-1 for BLAKE2b, 0 to 2^48-1 for BLAKE2s, 0 for the first, leftmost, leaf, or in sequential mode).
  • node_depth (0): node depth (0 to 255, 0 for leaves, or in sequential mode).
  • inner_length (0): inner digest length (0 to 64 for BLAKE2b, 0 to 32 for BLAKE2s, 0 in sequential mode).
  • key: key string for keyed hashing (up to 64 bytes for BLAKE2b, up to 32 bytes for BLAKE2s).
  • hash_length: optional, for reducing the length of the output hash.

NOTE: the salt and personal options are zero-padded so 'foo' is the same value as 'foo\0' or 'foo\0\0' with them (not so with key).

See section 2.10 in BLAKE2 specification for comprehensive review of tree hashing.