GRID for programmers

Hello there,

since I can't create a giveaway for the racing game GRID (removed from Steam shop due to some expired license, but the key should still work), I decided to put it behind a puzzle. Since I didn't want to create any accounts on puzzle sites, I just shuffled it in a reversible way. If you can write C++ you are certainly at an advantage, but I kept it simple so that any language will do. If you are determined even a spreadsheet calculator should work, but you probably won't be the first to solve then.

I put the key into a char array:

char key[] = "...";

And then shuffled it through this function:

void ShuffleKey(char* key)
{
    int len  = (int) strlen(key);
    int seed = 0;

    for (int i = 0; i < len; ++i)
    {
        seed += (int) key[i];
    }

    while (len > 0)
    {
        seed = (unsigned int) (seed * 87623 + 765214) % 234679661;

        int i = seed % len;
        int j = len - 1;

        char ki = key[i];
        char kj = key[j];

        key[i] = kj;
        key[j] = ki;

        len--;
    }
}

The resulting shuffled key is "-H3X-HAC3CMQ8KJMQ" without the quotes. The first one to successfully reverse the shuffle (I verified that it is possible with the given information) can activate the key. It would be nice if you drop an info if you activated it for others to know it's gone.

Edit: the key has been activated (thank you @ederlobo for the information), but of course you can solve for the challenge itself.