Arduino DUE native USB serial number

How to set USB serial number to Due's? I found VID&PID, manufacturer, but where is USB serial number?

In USBAPI.h: iSerialNumber = 0, i.e. No serial string.

Could you give me more details? I can't find "iSerialNumber" In what way I can provide custom serial number, or any serial number?

ISerialNumber is the 16th byte in Device Descriptor (page 263 of Universal Serial Bus Specification Revision 2.0

The question is how to set USB serial number from Code. I've found in USBDesc.h
#define ISERIAL 3
but this is only "index" value, i don't know where can I input serial number string value, used in descriptor.
My target is to use uniqe id of SAM3x as USB device serial number