Buddy, code what you give, is shifted pubkey to zero, or not ? I think sghift key to zero mean what from pubkey deducted a range, or I mistaken in this ?
I write p.s. above that Kangaroo app automaticly shift range and pubkey if begin range is not zero. You not need to do this manualy.
Ofcourse if you want you can do this manualy. Shift range and pubkey mean substract beginrange from range and from pubkey.