search.c

#include <openssl/aes.h>
#include <string.h>
#include <stdio.h>
unsigned char zero[16];
unsigned char scrambledzero[16];
unsigned char ciphertext[16];
double weight[16][256];
double maxweight[16];
unsigned char key[16];
AES_KEY expanded;
void doit(int b)
{
    int x;
    if (b == 16) {
        AES_set_encrypt_key(key,128,&expanded);
        AES_encrypt(zero,scrambledzero,&expanded);
        if (!memcmp(scrambledzero,ciphertext,16)) {
            printf("The key is");
            for (x = 0;x < 16;++x) printf(" %02x",key[x]);
            printf(".\n");
        }
        return;
    }
    for (x = 0;x < 256;++x)
        if (weight[b][x] == maxweight[b]) {
            key[b & 15] = x;
            doit(b + 1);
        }
}

int main()
{
    int b;
    int x;
    int n;
    int i;
    for (b = 0;b < 16;++b) {
        scanf("%x",&x);
        ciphertext[b] = x;
    }
    while (scanf("%d",&n) == 1) {
        scanf("%d",&b);
        for (i = 0;i < n;++i) {
            scanf("%x",&x);
            weight[b & 15][x & 255] += 1.0 / n;
        }
    }
    for (b = 0;b < 16;++b)
        for (x = 0;x < 256;++x)
            if (weight[b][x] > maxweight[b])
                maxweight[b] = weight[b][x];
    doit(0);
    return 0;
}