keyexpansionforshortest.hpp

是密码学加减密中中的重要算法

#include <iostream>
#include "Sbox.hpp"

const int Nk = 4 ;
const int Nr = 10 ;

template <typename T> //for Nk <= 6
void KeyExpansionForShorter (T key[4][Nk], T word[4][Nb * (Nr + 1)])
{
	int i = 0, j = 0 ; //循环变量

	for (j = 0; j < Nk; ++j)
	{
		for(i = 0; i < 4; ++i)
		{
			word[i][j] = key[i][j] ;
		}
	}
	
	for (j = Nk; j < Nb * (Nr + 1); ++j)
	{
		if (j % Nk == 0)
		{
			word[0][j] = word[0][j - Nk] ^ Sbox[word[1][j - 1]] ^ Rc[j/Nk] ;
			
			for (i = 1; j < 4; ++i)
			{
				word[i][j] = word[i][j - Nk] ^ Sbox[word[(i + 1) % 4][j - 1]] ;
			}
		}

		else
		{
			for (i = 0; j < 4; ++i)
			{
				word[i][j] = word[i][j - Nk] ^ word[i][j - 1] ;
			}
		}
	}
}