Secure near field communications

• US 9,883,383 B1
• Filed: 01/27/2017
• Issued: 01/30/2018
• Est. Priority Date: 01/27/2017
• Status: Active Grant

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Inventors: Chintalapudi, Krishna Kant, Priyantha, Nissanka Arachchige Bodhi
• Primary Examiner(s): Patel, Mahendra
• Application Number:
  US15/418,590
• Time in Patent Office: 368 Days
• Field of Search: 455411, 37935509, 307 105
• CPC Class Codes: H04B 5/72 for local intradevice communication
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer
• CPC Class Codes: H04W 12/033 of the user plane, e.g. user's traffic
• CPC Class Codes: H04W 12/037 of the control plane, e.g. signalling traffic
• CPC Class Codes: H04W 12/041 Key generation or derivation
• CPC Class Codes: H04W 4/80 Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication

Abstract

The security of Near Field Communications (NFC) against eavesdroppers is improved by encoding a hidden key, private to an initiating device, onto the carrier wave when a target device communicates its data via the carrier. The initiating device, in possession of the hidden key, is enabled to undo the scrambling effects of the hidden key to thereby privately interpret the data encoded onto the carrier wave by the target device. In various aspects, the hidden key is a one-time-use key that is randomly generated, used, and then discarded, preventing malicious parties from gaining the hidden key to later interpret intercepted data signals.

Claims

1. A method for securing Near Field Communications (NFC), comprising:

magnetically inducing, by an initiating device, an NFC carrier wave with a target device;

initiating, by the initiating device, a handshake procedure with the target device;

generating, on the initiating device, a hidden key;

modulating the NFC carrier wave, by the initiating device, according to the hidden key;

receiving, by the initiating device from the target device, a data signal encoded on the NFC carrier wave modulated by the hidden key and the data signal; and

interpreting, by the initiating device, the NFC carrier wave according to the hidden key to return the data signal encoded on the NFC carrier wave.

2. The method of claim 1, wherein the hidden key is generated as a series of random bits, wherein each random bit is discarded by the initiating device after being used to modulate the NFC carrier wave for a given time frame and interpret the NFC carrier wave for the given time frame.

3. The method of claim 1, wherein the NFC carrier wave is interpreted according to the hidden key to return the data signal by:

modulating a decoding threshold by the hidden key to produce a modulated threshold; and

comparing the NFC carrier wave against the modulated threshold to return the data encoded on the NFC carrier wave.

4. The method of claim 1, wherein the NFC carrier wave is interpreted according to the hidden key to return the data signal by:

demodulating the NFC carrier wave by the hidden key; and

comparing the demodulated NFC carrier wave against a static decoding threshold to return the data signal encoded on the NFC carrier wave.

5. The method of claim 1, wherein in response to determining that the target device has stopped encoding the data signal onto the NFC carrier wave, ceasing modulation, by the initiating device, of the NFC carrier wave according to the hidden key.

6. The method of claim 5, wherein it is determined by the initiating device that the target device has stopped encoding the data onto the NFC carrier wave according to at least one of:

an end-of-signal message encoded onto the NFC carrier;

or

a message length encoded onto the NFC carrier indicating a number of bits comprising the data signal.

7. The method of claim 1, wherein the initiating device begins modulating the NFC carrier according to the hidden key in response to at least one of:

a timed delay from an end of the handshake procedure;

or

a start-of-signal message encoded onto the NFC carrier.

8. The method of claim 1, wherein a length in bits of the hidden key and a length in bits of the data signal are equal.

9. The method of claim 1, wherein the initiating device provides power to the target device via the NFC carrier wave.

10. An actively communicating device providing secure Near Field Communications (NFC) with a passively communicating device, the actively communicating device comprising:

an antenna, configured to send and receive radio frequency signals;

a key buffer, configured to store a hidden key;

a modulator, in communication with the antenna and the key buffer, wherein the modulator is configured to;

produce a magnetic carrier wave transmitted via the antenna for communication with the passively communicating device;

encode a handshake signal onto the magnetic carrier wave to initiate communications with the passively communicating device; and

in response to receiving a response to the handshake signal from the passively communicating device, encode the hidden key onto the magnetic carrier wave; and

a demodulator in communication with the antenna and the key buffer, wherein the demodulator is configured to;

interpret the response from the passively communicating device by decoding a data signal encoded onto the magnetic carrier wave by the passively communicating device in light of the hidden key.

11. The actively communicating device of claim 10, wherein interpreting the response in light of the hidden key includes:

demodulating the magnetic carrier wave according to the hidden key to produce a demodulated carrier wave;

comparing an amplitude of the demodulated carrier wave to a decoding threshold across as series of timeframes;

in response to the amplitude of the demodulated carrier wave exceeding the decoding threshold at a given timeframe of the series of time frames, determining a value of the data signal at the given time frame to be ONE/TRUE; and

in response to the decoding threshold exceeding the amplitude of the demodulated carrier wave at the given timeframe of the series of time frames, determining the value of the data signal at the given time frame to be ZERO/FALSE.

12. The actively communicating device of claim 10, wherein interpreting the response in light of the hidden key includes:

modulating a decoding threshold according to the hidden key to produce a modulated threshold;

comparing an amplitude of the magnetic carrier wave to the modulated threshold across as series of timeframes;

in response to the amplitude of the magnetic carrier wave exceeding the modulated threshold at a given timeframe of the series of time frames, determining a value of the data signal at the given time frame to be ONE/TRUE; and

in response to the modulated threshold exceeding the amplitude of the magnetic carrier wave at the given timeframe of the series of time frames, determining the value of the data signal at the given time frame to be ZERO/FALSE.

13. The actively communicating device of claim 10, wherein the carrier wave transmits power to the passively communicating device.

14. The actively communicating device of claim 10, wherein the handshake signals an active device to enter a passive communication mode to act as the passively communicating device.

15. The actively communicating device of claim 10, wherein the key buffer is further configured to:

generate a series of random bits for use as the hidden key; and

discard each random bit of the series of random bits in response to decoding the data signal encoded onto the magnetic carrier wave.

16. A system for securing Near Field Communications (NFC), comprising:

a processor; and

a memory storage device including instructions, which when executed by the processor are operable to provide;

a modulator, configured to generate a carrier wave and encode data onto the carrier wave;

a demodulator, configured to observe the carrier wave to interpret data signals encoded onto the carrier wave;

a key buffer in communication with the modulator and the demodulator, configured to store a hidden key;

wherein the hidden key is encoded onto the carrier wave by the modulator to scramble a data signal received from a target device; and

wherein the hidden key is used by the demodulator to unscramble the data signal received from the target device.

17. The system of claim 16, wherein the modulator and demodulator operate according to an Amplitude Modulation scheme to encode and interpret data signals.

18. The system of claim 17, wherein the demodulator is further configured to interpret data signals encoded on the carrier wave against an amplitude threshold to determine a bit value of a given data signal at a given time frame, wherein the amplitude threshold is modulated according to the hidden key.

19. The system of claim 16, wherein the key buffer is further configured to:

generate the hidden key as a series of bits having randomly assigned binary values, wherein each bit corresponds to a given time frame for the carrier wave; and

in response to the demodulator unscrambling the data signal at the given time frame, remove the bit corresponding to the given time frame from storage.

20. The system of claim 16, wherein the modulator is further configured to modulate the carrier wave to produce a handshake signal unscrambled by the hidden key.