GMac
The GMAC specialisation of Galois/Counter mode (GCM) detailed in NIST Special Publication
800-38D.
Creates a GMAC based on the operation of a block cipher in GCM mode.
Creates a GMAC based on the operation of a 128 bit block cipher in GCM mode.
Initialises the GMAC - requires a ParametersWithIV
providing a KeyParameter and a nonce.