Input to be hashed. Can be a single string or a raw vector.
key
An optional key. Should be NULL (for no key), a single string, or a
raw vector.
Value
The hash of the string as a raw vector.
References
Aumasson, J.P., Neves, S., Wilcox-O'Hearn, Z. and Winnerlein, C., 2013, June.
BLAKE2: simpler, smaller, fast as MD5. In International Conference on Applied
Cryptography and Network Security (pp. 119-135). Springer Berlin Heidelberg.