Hi,
If the stores does not have access to Internet, I am not sure that HikaSerial will be the right solution.
HikaSerial have some web services so it is possible to check if a serial is valid or not without having access to the backend, but a access to the website is required.
It is possible to implement a special serial generator in order to have serial with some "security" (or checks) but it will be difficult to know if the serial has been already used or not without checking it in a central database.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.