void key_decode (const u8 *key, u8 *deckey) {
    u8  seq []   = {8, 10, 4, 5, 7, 1, 11, 3, 9, 2, 0, 6};
    s8  i        = 11;
    u8  j        = 0, k = 0;
    u32 v        = 330078017;
    while (i > -1) {
	j = key [seq [k++]];
	if (j < 8) {
	    j ^= v & 7;
	    v >>= 3;
	} else
	    j ^= i & 1;
	deckey [i--] = j;
    }
}