SPN

#include <stdio.h>
#include <stdlib.h>
#define size_x 6
#define size_y 4
#define N 16

void bintohex(int input[] , char output[])
{
    int i,j,k,loop,value;
    for(i = 0 , k = 0 ; i < N ; i += 4)
    {
        for(loop = 3 , j = i , value = 0 ; loop >= 0  ; j++ , --loop)
            value += input[j] << loop;
        //printf("%d\n",value);
        if (value < 10)
            output[k++] = value + 0x30;
        else
        {
            value -= 10;
            output[k++] = value + 0x30 + 0x11;
        }
    }
    for(i = 0 ; i < k ; i++)
    {
        printf("%c",output[i]);
    }
    puts("");

}
void hextobin(char (*p)[size_y] , int output[])
{
    char *c;
    int i,j,k,value,loop;
    for(c = &p[0][0] , j = 3 , loop = 0  ; loop < 4  ; c++ , j += 4 , loop++)
    {
        if (*c >= 'A' && *c <= 'F')
            value = *c - 0x0  - 7;
        else
            value = *c - 0x0;
        for(k = 0 , i = j ; k <= 3 ; k++ , i--)
        {
            *(output+i) = value % 2;
            value /= 2;
        }
    }
    /*
    for(i = 0 ; i < N ; i++)
        printf("%d ",*(output+i));
    printf("\n");
    */
}
void Subkey(int input1[] , int input2[] , int output[])
{
    int i;
    for(i = 0 ; i < N ; i++)
        output[i] = input1[i] ^ input2[i];
    /*
    printf("Subkey   ");
    for(i = 0 ; i < N ; i++)
        printf("%d ",output[i]);
    puts("");
    */
}

void sBox(int input[] , char S[] , char output[])
{
    int i,j,k,loop;
    int value;
    for(i = 0 , k = 0 ; i < N ; i += 4 , k++)
    {
        for(loop = 3 , j = i , value = 0 ; loop >= 0  ; j++ , --loop)
        {
            value += input[j] << loop;
        }
        output[k] = S[value];
    }
}
void pBox(int input[] , int P[] , int output[])
{
    int i,j,k,loop;
    int value;
    int num;
    //puts("P-Box       ");
    for(i = 0 ; i < N ; i++)
    {
        output[P[i]] = input[i];
    }
    /*
    for(i = 0 ; i < N ; i++)
    {
        printf("%d",output[i]);
    }
    puts("");
    */
}
int main()
{
    char S1[N] = {'E','4','D','1','2','F','B','8','3','A','6','C','5','9','0','7'};
    char S2[N] = {'E','3','4','8','1','C','A','F','7','D','9','6','B','2','0','5'};
    int P[N] = {0,4,8,12,1,5,9,13,2,6,10,14,3,7,11,15};
    int sub[N];         /* Substitution results           */
    int per[N];         /* Permutation results            */
    int n1[N],n2[N];    /* Substitution input             */
    int round;
    char input[6][4];   /* Divide sequence to input array */
    char ch[4];     /* Temporaily sBox output         */
    char p[100];        /* Original sequence array        */
    char *c;
    int i,j,k;
    int cond;        /* Determine this program is Encrypt or Decrypt */
    //printf("Encryption/Decryption please enter (1/0): ");
    //scanf("%d",&cond);
    while(1)
    {
        scanf("%d",&cond);
        getchar();
        gets(p);
        for(c = p , i = 0 , j = 0 ; *c ; c++ )
        {
            if (*c == ' ')
                continue;
            input[i][j++] = *c;
            if (j % 4 == 0)
            {
                j = 0;
                i++;
            }
        }
        if (cond == 1)
        {
            for(round = 0 , i = 0 , j = 0 ; round < 3  ;  round++)
            {
                if (round == 0)
                {
                    hextobin(&input[i] , n1);
                    hextobin(&input[++i] , n2);
                }
                else
                {
                    hextobin(&input[++i] , n2);
                }
                Subkey(n1 , n2 , sub);
                sBox(sub , S1 , ch);
                for(j = 0 ; j < size_y ; j++)
                    *(*(input + i) + j) = ch[j];
                hextobin(&input[i] , per);
                pBox(per , P , n1);
            }
            hextobin(&input[++i] , n2);
            Subkey(n1 , n2 , sub);
            sBox(sub , S1 ,ch);
            hextobin(&input[++i] , n2);
            for(j = 0 ; j < size_y ; j++)
                *(*(input + i) + j) = ch[j];
            hextobin(&input[i] , per);
            Subkey(per , n2 , sub);
            bintohex(sub , ch);
        }
        else if (cond == 2)
        {
            hextobin(&input[0] , n1);
            hextobin(&input[--i] , n2);
            Subkey(n1 , n2 , sub);
            sBox(sub , S2 , ch);
            for(j = 0 ; j < size_y ; j++)
            {
                *(*(input + 0) + j) = ch[j];
            }
            hextobin(&input[--i] , n2);
            hextobin(&input[0] , n1);
            Subkey(n1 , n2 , sub);
            for(--i ; i > 0 ; --i)
            {
                pBox(sub , P , per);
                sBox(per , S2 , ch);
                for(j = 0 ;  j < size_y ; j++)
                    *(*(input + 0) + j) = ch[j];
                hextobin(&input[0] , n1);
                hextobin(&input[i] , n2);
                Subkey(n1 , n2 , sub);
            }
            bintohex(sub , ch);
        }
        else
            break;
    }

    return 0;
}