A system determines an electronic product code (EPC) and a checksum read from a radio-frequency identification (RFID) tag. The system calculates a new checksum based on the EPC and a retailer-specific number associated with a retailer that owns one or more RFID tags. The system compares the new checksum with the checksum read from the RFID tag, and determines whether the RFID tag is owned by the retailer based on whether the new checksum matches the checksum read from the RFID tag.
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