Extracting .jic from cyclone III

someone could read out the SPI flash, clone your board, and duplicate your product

some families support encryption of the configuration file (Cyclone III not included, but Cyclone III LS included) which helps mitigate this sort of problem

alternatively you could develop your own basic key exchange type scheme where a CPLD or microcontroller generates a PN code and sends it over to the FPGA which is matching the PN codes. if the match is not made, the FPGA design breaks (maybe it disables an enable signal somewhere). reading the CPLD or uC will be significantly harder than reading a small flash