CodeGate 2012 Quals – Binary 200

#include <stdio.h>
#include <time.h>
 
#define uint32_t unsigned int
int prem_data(unsigned int *new_key, unsigned char* key)
{
  int result, i;
  result = 0;
  new_key[0] = 0;
  new_key[1] = 0;
  new_key[2] = 0;
  new_key[3] = 0;
  for ( i = 0; i < 4; ++i )
  {
    result = i;
    new_key[i] = key[4*i+3] | (key[4*i+2] << 8) | (key[4*i+1] << 16) | (key[4*i] << 24);
  }
  return result;
}
void decrypt4 (uint32_t* v, uint32_t* k, unsigned char* new_keys) 
{
    uint32_t v0=v[0], v1=v[1], sum=0xC6EF3720, i;  /* set up */
    uint32_t delta=0x61C88647;                     /* a key schedule constant */
    uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3];   /* cache key */
 
    unsigned char* vv = (unsigned char*)v;
    v0 = vv[3] | (vv[2] << 8) | (vv[1] << 16) | (vv[0] << 24);
    v1 = vv[7] | (vv[6] << 8) | (vv[5] << 16) | (vv[4] << 24);
 
    for (i=0; i < 0x20; i++) 
    {                 
	v1 -= (((v0<<4)^(v0>>5)) + v0) ^ (sum + k[(sum>>11) & 3]);
	sum += delta;                                   
	v0 -= (((v1<<4)^(v1>>5)) + v1) ^ (sum + k[sum & 3]);                                 
 
    }                                              /* end cycle */
    v[0]=v0; v[1]=v1;
 
    new_keys[0] = (unsigned char)(v0 >> 24);
    new_keys[1] = (unsigned char)(v0 >> 16);
    new_keys[2] = (unsigned char)(v0 >> 8);
    new_keys[3] = (unsigned char)v0;
    new_keys[4] = (unsigned char)(v1 >> 24);
    new_keys[5] = (unsigned char)(v1 >> 16);
    new_keys[6] = (unsigned char)(v1 >> 8);
    new_keys[7] = (unsigned char)(v1);
}
unsigned char g_data[17]   = "\x1E\xa0\xf5\xc6\xD9\xec\x02\xf6\x59\x18\x7c\x2e\x6f\x85\x5d\xde";
unsigned char hardcoded_keys[17] = "\x1E\xAE\xA1\xC7\xB3\x50\x6D\x02\x5A\x61\x33\xE4\x5B\xF0\x13\x8A";
void main()
{
	unsigned char tmp_data[17];
	prem_data((uint32_t*)tmp_data, g_data);
	decrypt4 ((uint32_t*)hardcoded_keys, (uint32_t*)tmp_data, (unsigned char*)tmp_data);
	tmp_data[8] = '\0';
	printf("Key: %s", tmp_data);
}

#include <stdio.h> #include <time.h> #define uint32_t unsigned int int prem_data(unsigned int *new_key, unsigned char* key) { int result, i; result = 0; new_key[0] = 0; new_key[1] = 0; new_key[2] = 0; new_key[3] = 0; for ( i = 0; i < 4; ++i ) { result = i; new_key[i] = key[4*i+3] | (key[4*i+2] << 8) | (key[4*i+1] << 16) | (key[4*i] << 24); } return result; } void decrypt4 (uint32_t* v, uint32_t* k, unsigned char* new_keys) { uint32_t v0=v[0], v1=v[1], sum=0xC6EF3720, i; /* set up */ uint32_t delta=0x61C88647; /* a key schedule constant */ uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */ unsigned char* vv = (unsigned char*)v; v0 = vv[3] | (vv[2] << 8) | (vv[1] << 16) | (vv[0] << 24); v1 = vv[7] | (vv[6] << 8) | (vv[5] << 16) | (vv[4] << 24); for (i=0; i < 0x20; i++) { v1 -= (((v0<<4)^(v0>>5)) + v0) ^ (sum + k[(sum>>11) & 3]); sum += delta; v0 -= (((v1<<4)^(v1>>5)) + v1) ^ (sum + k[sum & 3]); } /* end cycle */ v[0]=v0; v[1]=v1; new_keys[0] = (unsigned char)(v0 >> 24); new_keys[1] = (unsigned char)(v0 >> 16); new_keys[2] = (unsigned char)(v0 >> 8); new_keys[3] = (unsigned char)v0; new_keys[4] = (unsigned char)(v1 >> 24); new_keys[5] = (unsigned char)(v1 >> 16); new_keys[6] = (unsigned char)(v1 >> 8); new_keys[7] = (unsigned char)(v1); } unsigned char g_data[17] = "\x1E\xa0\xf5\xc6\xD9\xec\x02\xf6\x59\x18\x7c\x2e\x6f\x85\x5d\xde"; unsigned char hardcoded_keys[17] = "\x1E\xAE\xA1\xC7\xB3\x50\x6D\x02\x5A\x61\x33\xE4\x5B\xF0\x13\x8A"; void main() { unsigned char tmp_data[17]; prem_data((uint32_t*)tmp_data, g_data); decrypt4 ((uint32_t*)hardcoded_keys, (uint32_t*)tmp_data, (unsigned char*)tmp_data); tmp_data[8] = '\0'; printf("Key: %s", tmp_data); }