private uint Stage(uint a, uint b, uint n)
{
uint x1 = (bf_s0[byteHelpers.GetFirstByte(b)] + bf_s1[byteHelpers.GetSecondByte(b)]) ^ bf_s2[byteHelpers.GetThirdByte(b)];
uint x2 = x1 + bf_s3[byteHelpers.GetFourthByte(b)];
uint x3 = x2 ^ bf_P[n];
return(x3 ^ a);
}