class mac : ?iv:string -> ?pad:Cryptokit.Padding.scheme -> block_cipher -> Cryptokit.hash
Build a MAC (keyed hash function) from the given block cipher.
The block cipher is run in CBC mode, and the MAC value is
the final value of the initialization vector.
Thus, the hash size of the resulting
hash is the block size of the block cipher.
The optional argument iv specifies the first initialization
vector, with a default of all zeroes. The optional argument
pad specifies a padding scheme to be applied to the input
data; if not provided, no padding is performed.