After the delivery buyer can verify those numbers as part of the proof that the package has not been tampered with (opened, swapped, or misdelivered). The link to the specially-crafted website with those unique numbers is programmed into the NFC chip (the NFC is located inside the package and cannot be reprogrammed or replaced). The website itself is a single HTML file with embedded JavaScript variables holding encrypted delivery details. The access to the data is secured by a PIN code, sent to the buyer after shipment. The file is stored on an IPFS network, the special type of peer-to-peer network where each file is addressed (handle) by content hash rather than the filename. In other words, any change to the file content will change the address. By the fact, the user gets the link to validate the delivery offline (by scanning the NFC chip attached inside the package, by an ordinary smart mobile phone) the whole validation process is offline as well.