ThreefishEngine
Implementation of the Threefish tweakable large block cipher in 256, 512 and 1024 bit block
sizes.
1024 bit block size - Threefish-1024
256 bit block size - Threefish-256
512 bit block size - Threefish-512
Constructs a new Threefish cipher, with a specified block size.
Initialise the engine.