Hashing

The Blake2b cryptographic hash function is the preferred one – it is faster than MD5 yet just as secure as SHA-3. Note that for password hashing or deriving keys from passwords, please use a PDKF like Argon2.

monocypher.hash.blake2b(msg, key=b'', hash_size=64)

Computes the Blake2b digest of the given msg, optionally with a key (which can be used to construct a message authentication code). The returned digest will have length hash_size.

Parameters:

• msg – The message (a bytes-like object).

• key – The key (bytes-like), between Blake2bContext.KEY_MIN and Blake2bContext.KEY_MAX long.

• hash_size – Digest length (int), between Blake2bContext.HASH_MIN and Blake2bContext.HASH_MAX. When using Blake2b as a MAC, anything below 16 is discouraged, and when using Blake2b as a general-purpose hash function, anything below 32 is discouraged.

Return type:

bytes

MAC Example

from monocypher.utils import random, crypto_verify16
from monocypher.hash import blake2b

KEY = random(64)

def compute_mac(msg):
    return blake2b(msg, key=KEY, hash_size=16)

def verify_mac(msg, mac):
    # Do not use "mac == compute_mac(msg)" here, since
    # we may leak some information about the real mac
    # (see timing attacks).
    return crypto_verify16(mac, compute_mac(msg))

Incremental Interface

from monocypher.hash import Blake2bContext
ctx = Blake2bContext()
with open('file', mode='rb') as f:
    while True:
        chunk = f.read(4096)
        if chunk == b'':
            break
        ctx.update(chunk)
digest = ctx.digest()

class monocypher.hash.Blake2bContext(data=b'', key=b'', hash_size=64)

Can be used to incrementally compute the blake2b hash of a long stream of bytes (e.g. a large file) without having to read all of it into memory. Parameters have the same meaning as blake2b(). This class is compatible with hashlib’s hash objects; see hashlib for details.

HASH_MAX = 64

Maximum Blake2b digest length

HASH_MIN = 1

Minimum Blake2b digest length

KEY_MAX = 64

Maximum Blake2b key length

KEY_MIN = 0

Minimum Blake2b key length