Abstract: Provided are a contactless communication tag, a portable tag reader, and a method of providing genuineness of a product. The tag reader specifies an encryption key corresponding to an encryption key stored in the tag from its own plurality of encryption keys based on a signal received from the tag. The tag reader receives an encrypted product code or product information from the tag and decrypts the received product code or product code using an encryption key. Also, the tag reader outputs a result of decryption on a 7-segment display window, a plurality of color light emitting diodes (LED), and/or a liquid crystal display (LCD) window or as beep sounds or voices.