xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx

    uuid += digits[(rand>>8)&0xF];
    uuid += digits[(rand>>12)&0xF];
    uuid += digits[(rand>>16)&0xF];
    uuid += digits[(rand>>20)&0xF];
    uuid += digits[(rand>>24)&0xF];
    uuid += digits[(rand>>28)&0xF];