sm4_sbox.c

#include <stdio.h>

int change(int x)
{
    int A1 = 0xA7;
    int flag;
    int result = 0;
    int tem;
    int flag2;
    for (int i = 0; i < 8; i++)
    {
        flag = (A1 & 0x80) >> 7;
        tem = x & A1;
        flag2 = 0;
        for (int j = 0; j < 8; j++)
        {
            flag2 ^= (tem & 1);
            tem >>= 1;
        }
        result = result | (flag2 << i);
        A1 = (A1 << 1) | flag;
    }
    result ^= 0xd3;
    return result;
}

int multiplication(int a, int b)
{
    int tem = 0;
    int i = 0;
    while (b)
    {
        if (b & 1)
        {
            tem ^= a << i;
        }
        i++;
        b >>= 1;
    }
    return tem;
}

int length(int x)
{
    int i = 0;
    int comp = 1;
    while (1)
    {
        if (comp >= x)
        {
            return i;
        }
        comp = (comp << 1) + 1;
        i++;
    }
}

void division(int a, int b, int *round, int *left)
{
    *round = 0;
    *left = 0;
    int distance;
    while (1)
    {
        distance = length(a) - length(b);
        if (distance >= 0 && a)
        {
            a = a ^ (b << distance);
            *round = (*round) | (1 << distance);
        }
        else
        {
            *left = a;
            break;
        }
    }
}

int inverse(int a, int b)
{
    int x2 = 1;
    int x1 = 0;
    int y2 = 0;
    int y1 = 1;
    int temX1, temY1;
    int q, r, x, y;
    int i;
    while (b)
    {
        division(a, b, &q, &r);
        //x=x2^multiplication(q,x1);
        y = y2 ^ multiplication(q, y1);
        a = b;
        b = r;
        //x2=x1;
        //x1=x;
        y2 = y1;
        y1 = y;
    }
    return y2;
}

int main(void)
{
    for (int i = 0; i <= 0xf; i++)
    {
        for (int j = 0; j <= 0xf; j++)
        {
            printf("0x%02x, ", change(inverse(0x1f5, change((i << 4) | j))));
        }
        printf("\n");
    }
    return 0;
}