Module

Creating hash objects

New hash objects are created by calling constructor functions:

pyblake2.blake2b(data=b'', digest_size=64, key=b'', salt=b'', person=b'', fanout=1, depth=1, leaf_size=0, node_offset=0, node_depth=0, inner_size=0, last_node=False)

pyblake2.blake2s(data=b'', digest_size=32, key=b'', salt=b'', person=b'', fanout=1, depth=1, leaf_size=0, node_offset=0, node_depth=0, inner_size=0, last_node=False)

These functions return the corresponding hash objects for calculating BLAKE2b or BLAKE2s. They optionally take these general parameters:

• data: initial chunk of data to hash, which must be interpretable as buffer of bytes.
• digest_size: size of output digest in bytes.
• key: key for keyed hashing (up to 64 bytes for BLAKE2b, up to 32 bytes for BLAKE2s).
• salt: salt for randomized hashing (up to 16 bytes for BLAKE2b, up to 8 bytes for BLAKE2s).
• person: personalization string (up to 16 bytes for BLAKE2b, up to 8 bytes for BLAKE2s).

The following table shows limits for general parameters (in bytes):

Hash	digest_size	len(key)	len(salt)	len(person)
BLAKE2b	64	64	16	16
BLAKE2s	32	32	8	8

Note

BLAKE2 specification defines constant lengths for salt and personalization parameters, however, for convenience, this implementation accepts byte strings of any size up to the specified length. If the length of the parameter is less than specified, it is padded with zeros, thus, for example, b'salt' and b'salt\x00' is the same value. (This is not the case for key.)

These sizes are available as module constants described below.

Constructor functions also accept the following tree hashing parameters:

• fanout: fanout (0 to 255, 0 if unlimited, 1 in sequential mode).
• depth: maximal depth of tree (1 to 255, 255 if unlimited, 1 in sequential mode).
• leaf_size: maximal byte length of leaf (0 to 2**32-1, 0 if unlimited or in sequential mode).
• node_offset: 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: node depth (0 to 255, 0 for leaves, or in sequential mode).
• inner_size: inner digest size (0 to 64 for BLAKE2b, 0 to 32 for BLAKE2s, 0 in sequential mode).
• last_node: boolean indicating whether the processed node is the last one (False for sequential mode).

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

Using hash objects

Hash objects have the following attributes and methods:

hash.digest_size

The size of the resulting digest in bytes. This is the value given to hash object constructor in digest_size argument.

hash.block_size

The internal block size of the hash algorithm in bytes.

hash.update(arg)

Update the hash object with the object, which must be interpretable as buffer of bytes

Note

For better multithreading performance, the Python GIL is released for data larger than 2047 bytes at hash object creation or on update to allow other threads to run.

hash.digest()

Return the digest of the data so far.

hash.hexdigest()

Like digest() except the digest is returned as a string of double length, containing only hexadecimal digits.

hash.copy()

Return a copy of the hash object.

Constants

pyblake2.BLAKE2B_SALT_SIZE

pyblake2.BLAKE2S_SALT_SIZE

Salt length (maximum length accepted by constructors).

pyblake2.BLAKE2B_PERSON_SIZE

pyblake2.BLAKE2S_PERSON_SIZE

Personalization string length (maximum length accepted by constructors).

pyblake2.BLAKE2B_MAX_KEY_SIZE

pyblake2.BLAKE2S_MAX_KEY_SIZE

Maximum key size.

pyblake2.BLAKE2B_MAX_DIGEST_SIZE

pyblake2.BLAKE2S_MAX_DIGEST_SIZE

Maximum digest size that the hash function can output.