void decodeKey (const unsigned char *key, unsigned char *deckey) {
    unsigned char seq [] = {6, 0, 2, 9, 3, 11, 1, 7, 5, 4, 10, 8};
    unsigned long n = 330078017;
    unsigned char i = 11;
    do {
	seq [i] = key [seq [i]];
	if (seq [i] < 8) {
	    seq [i] ^= n & 7;
	    n >>= 3;
	} else
	    seq [i] ^= i & 1;
	deckey [i] = seq [i];
    } while (i--);
}