Nfc device capable of authenticating received message, method thereof, and nfc self-payment method using the same

A Near Field Communication (NFC) reader comprising:

• a memory configured to store a key;
• an antenna configured to receive a message and a first message authentication code (MAC) transmitted from an NFC tag;
• a communication circuit configured to receive the message and the first MAC from the antenna;
• and
• a processor configured to receive the message and the key and determine whether each of a length of the message and a length of the key is an integer multiple of a processing unit,
• wherein the processor configured to:
• generate, when the length of the message is not m-times the processing unit, a correction message including m-processing units by inserting first padding bits into the message so that the length of the message becomes m-times the processing unit,
• generate, when the length of the key is not n-times the processing unit, a correction key including n-processing units by inserting second padding bits into the key so that the length of the key becomes n-times the processing unit, and
• divide the correction key into a first part and a second part,
• wherein the processing unit is k bits, each of m and n is a natural number equal to or greater than one, and k is a natural number equal to or greater than two.

A method of authenticating a message of a Near Field Communication (NFC) tag using an NFC reader storing a key, comprising:

• receiving, by the NFC reader, the message and a first message authentication code (MAC) from the NFC tag when the NFC tag is tagged by the NFC reader;
• generating, by the NFC reader, a correction message including m-processing units by inserting first padding bits into the message so that a length of the message becomes m-times the processing unit;
• generating, by the NFC reader, a correction key including n-processing units by inserting second padding bits into the key so that a length of the key becomes n-times the processing unit;
• and dividing, by the NFC reader, the correction key into a first part and a second part,
• wherein the processing unit is k bits, each of m and n is a natural number equal to or greater than one, and k is a natural number equal to or greater than two.

A Near Field Communication (NFC) self-checkout method using an NFC system,

• wherein the NFC system includes:
• a first NFC tag configured to store a first key, a first message, and a first message authentication code (MAC) and is attached to a product,
• a second NFC tag configured to store a second key identical to the first key, a second message, and a second MAC, and is installed in a store,
• an NFC mobile device that includes a processor configured to execute a shopping cart program for NFC self-checkout;
• and
• a web server configured to store a third key identical to the first key,
• wherein the NFC self-checkout method includes:
• receiving, by the NFC mobile device, the second message including a web address corresponding to the web server and store information and the second MAC from the second NFC tag and transmitting the second message and the second MAC to the web server when the second NFC tag is tagged by the NFC mobile device;
• generating, by the web server, a third MAC by applying the third key to the second message;
• comparing, by the web server, the second MAC and the third MAC;
• and
• controlling, by the web server, the NFC mobile device so that the shopping cart program is executed when the second MAC and the third MAC are identical.