For example, how can we avoid the cloning of hotel key cards?
There are different ways to do this, using cryptographic keys. Intrinsic ID employs physical unclonable functions (PUFs) to differentiate chips from each other. The system utilizes tiny differences in the chip itself to create a unique identifier, as well as a cryptographic key that is different from the RFID tag's unique serial number. When the tag sends its serial number to the reader, the latter requests the unique cryptographic key, which cannot be cloned. A transaction is only authorized if the correct key is received. NXP Semiconductors has incorporated PUF technology into its SmartMX2 ICs (see RFID News Roundup: NXP Strengthens SmartMX2 Security Chips With PUF Anti-cloning Technology).
Another way is to use an RFID tag that supports encryption technology. Tags and readers based on the ISO 14443 standard support encryption. These systems work essentially the same way as the tags described above—the reader requests a key and only authorizes the transaction if it receives the correct key in response. But the key is not generated from any physical differences in the tag. If the encryption scheme were cracked, you could clone these tags as well and send the correct key using a cloned card.
—Mark Roberti, Founder and Editor, RFID Journal
Previous Post Where Can I Buy Passive RFID Seals? »