encrypted code generator example

//
// A program that generates encrypted executable code and a key for use in C
//  Written by: MadMouse

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <time.h>


// a generic mix algorithm for seeding the random number generator
long unsigned int mix(long unsigned int a, long unsigned int b, long unsigned int c)
{
    a=a-b;  a=a-c;  a=a^(c >> 13);
    b=b-c;  b=b-a;  b=b^(a << 8);
    c=c-a;  c=c-b;  c=c^(b >> 13);
    a=a-b;  a=a-c;  a=a^(c >> 12);
    b=b-c;  b=b-a;  b=b^(a << 16);
    c=c-a;  c=c-b;  c=c^(b >> 5);
    a=a-b;  a=a-c;  a=a^(c >> 3);
    b=b-c;  b=b-a;  b=b^(a << 10);
    c=c-a;  c=c-b;  c=c^(b >> 15);
    return c;
}

// a semi reasonable seeding function
void seed_prng(void)
{
    unsigned int urandom;
    FILE* urandomF = fopen("/dev/urandom", "r");
    fread(&urandom, sizeof(int), 1, urandomF);
    fclose(urandomF);
    long unsigned int seed = mix(clock(), urandom, getpid());

    srand(seed);
    return;
}

int main(void)
{
const char evil[] = "INSERT CODE HERE";


    int i;

    char key[sizeof(evil)];

    printf("\n// key data\nBYTE key[] = \"");   // print out a comment and start description of our data
    for(i=0;i<sizeof(evil);i++)     // for the size of evil payload
    {
        seed_prng();            // get some randomness
        key[i] = rand()%255;        // write a random byte to the key
        printf("\\x%02x",0xFF&(key[i]));    // print it out
    }

    printf("\";\n// encrypted code\nBYTE evil[] = \""); // same fluff as before
    for(i=0;i<sizeof(evil);i++)
    {
        printf("\\x%02x",0xFF&(key[i]^evil[i])); // xor the curretn key byte with the current evil byte
    }
    printf("\";\n\nsize: %i\n\n",i);    // print out the size so that we can set up offsets later

    return 0;   // WOOOT, all done ;)
}