Keyed hashing can be used for authentication as a faster and simpler replacement for Hash-based message authentication code (HMAC). BLAKE2 can be securely used in prefix-MAC mode thanks to the indifferentiability property inherited from BLAKE.
>> from hashlib import blake2b
>> secret = 'naisho'
>> sessionid = 'session-123456'
>> h = blake2b(key=secret.encode(), digest_size=8)