The Structure of SAFER+ Algorithm for Encryption Round i
�xor� denotes bit-by-bit modulo-two addition of bytes
�add� denotes modulo-256 addition of bytes
�exp� denotes 45x modulo 257, with the convention
that the result 45128=256 is represented by 0
�log� denotes log45(x), with the convention that log45(0)=128