Methods of transmitting information from efficient encryption card readers to mobile devices

• US 9,582,795 B2
• Filed: 11/17/2011
• Issued: 02/28/2017
• Est. Priority Date: 02/05/2002
• Status: Active Grant

• Current Assignee: Block, Inc. (f/k/a Square, Inc.)
• Original Assignee: Square Inc (Block, Inc. (f/k/a Square, Inc.))
• Inventors: Dorsey, Jack, McCauley, Nathan P., Cummins, Justin Phillip, Monica, Diego, Quigley, Oliver Samuel Curran, McKelvey, James M.
• Primary Examiner(s): Le, Thien M
• Assistant Examiner(s): TAYLOR, APRIL ALICIA
• Application Number:
  US13/298,525
• Publication Number:
  US 20120126005A1
• Time in Patent Office: 1,930 Days
• Field of Search: 235/375, 235380-382, 235/435, 235/439, 235/449
• US Class Current: 1/1
• CPC Class Codes: G06Q 20/322 Aspects of commerce using mobile devices [M-devices]
• CPC Class Codes: G06Q 20/347 Passive cards
• CPC Class Codes: G06Q 30/06 Buying, selling or leasing transactions
• CPC Class Codes: G06Q 40/02 Banking, e.g. interest calculation or account maintenance credit or loans G06Q40/03
• CPC Class Codes: G07F 7/0886 the card reader being portable for interacting with a POS or ECR in realizing a payment transaction

Abstract

A method of transmitting encrypted information to a mobile device and a payment service uses a card reader. The card reader has device electronics that include a microcontroller with logic resources with code and an output jack. A raw magnetic head signal is received from a reading of the card in the slot. The raw magnetic head signal is converted into a processed digital signal that the microcontroller can interpret. The logic resources and the code create both an encryption and signed signal. An encrypted and signed output jack message is delivered to the mobile device through the output jack based on the contents of the signal, with at least a portion of the output jack signal being encrypted.

Claims

1. A method of transmitting encrypted information to a mobile device and a payment service, comprising:

receiving a raw magnetic head signal at a card reader from a reading of a magnetic stripe of a card in a slot of the card reader, the card reader including device electronics that includes a microcontroller with logic resources with code and an audio output jack;

powering a power subsystem of the card reader by a microphone bias voltage signal of the mobile device, wherein the power subsystem is configured to convert the microphone bias voltage signal into a system voltage signal that enables the device electronics to operate;

converting the raw magnetic head signal into a processed digital signal that the microcontroller can interpret;

using the logic resources with code to encrypt the processed digital signal within the card reader, the code including a two-pass block cipher that uses a unique identifier and a cryptographic key to encrypt the processed digital signal; and

delivering an encrypted output jack signal based on contents of the processed digital signal to the mobile device through the audio output jack of the card reader, with at least a portion of the encrypted output jack signal being encrypted by the two-pass block cipher using the unique identifier and the cryptographic key.

2. The method of claim 1, further comprising:

creating messages that can contain encrypted and non-encrypted data, and contain a signature that can be used to verify that data has not been modified.

3. The method of claim 1, wherein the code includes countermeasures to detect tampering and attacks on the card reader.

4. The method of claim 1, further comprising:

having the card reader disable itself when modification or tampering is detected.

5. The method of claim 1, wherein the code is no more than 8 kilobytes in size.

6. The method of claim 1, further comprising:

expanding the cryptographic key before programming, and the microcontroller code does not include or require key expansion functionality.

7. The method of claim 1, further comprising:

using the microcontroller to recalculate a bit period in real time to capture variable-speed swipes.

8. The method of claim 1, further comprising:

using the microcontroller to parse and error-check card data.

9. The method of claim 1, further comprising:

using the microcontroller to run periodic checksums on code and memory.

10. The method of claim 1, further comprising:

using thresholds to filter out erroneous data and/or false edges.

11. The method of claim 1, further comprising:

using the microcontroller to determine 1′

s and 0′

s by checking a frequency of polarity changes within a bit period.

12. The method of claim 1, wherein the device electronics includes an analog to digital front-end.

13. The method of claim 12, wherein the analog to digital front end is coupled to a processing element in the microcontroller, the analog to digital front end receiving a raw magnetic head signal and converting the raw magnetic head signal into a processed digital signal that the microcontroller can interpret, the microcontroller producing a signal.

14. The method of claim 12, wherein the analog to digital front end is configured to capture card readings that are swept at a rate of 5 inches to 50 inches per second.

15. The method of claim 12, wherein the analog to digital front end includes, an amplifier/filter, differentiator and a comparator.

16. The method of claim 15, wherein the analog to digital front end further includes wake-up electronics.

17. The method of claim 16, wherein the wake-up electronics is a wake-up circuit.

18. The method of claim 1, wherein the encrypted output jack signal is a synchronous Manchester encoded stream.

19. The method of claim 1, wherein the encrypted output jack signal is an asynchronized stream.

20. The method of claim 1, wherein the encrypted output jack signal is at a frequency that the output jack signal appears to look AC to a microphone input of the mobile device.

21. The method of claim 1, wherein a frequency of the encrypted output jack signal is 2 KHz to 48 kHz.

22. The method of claim 1, wherein a frequency of the encrypted output jack signal is 2.4 kHz.

23. The method of claim 1, wherein the microcontroller has a non-volatile memory with a size of 2-8 kbytes, and RAM with a size 128-512 bytes.

24. The method of claim 1, wherein the card reader sends the encrypted output jack signal to the mobile device at a constant baud rate.

25. The method of claim 24, wherein the constant baud rate is 2400 to 9200 baud.

26. The method of claim 1, further comprising:

a power source coupled to wake-up electronics.

27. The method of claim 1, further comprising:

using the microphone bias voltage signal both for powering the power subsystem of the card reader and for transmitting data from the card reader back to the mobile device.

28. The method of claim 1, wherein the microphone bias voltage signal is a direct current (DC) voltage signal, and wherein converting the microphone bias voltage signal into a system voltage signal comprises a DC to DC conversion.

29. A card reader, comprising:

a read head configured to receive a raw signal from a reading of a card;

device electronics configured to convert the raw signal into a digital signal that a microcontroller can interpret, the microcontroller including logic resources for encrypting the digital signal within the card reader via a two-pass block cipher that uses a unique identifier and a cryptographic key to perform encryption of the digital signal;

a power subsystem for powering the card reader using a microphone bias voltage signal of a mobile device, wherein the power subsystem is configured to convert the microphone bias voltage signal into a system voltage signal that enables the device electronics to operate; and

an audio output jack for delivering an output jack signal to the mobile device, wherein the output jack signal is based at least in part on contents of the raw signal, and wherein at least a portion of the output jack signal is encrypted by the two-pass block cipher using the unique identifier and the cryptographic key.

30. The card reader of claim 29, wherein the microcontroller is configured to create a message containing a signature for verifying that data has not been modified, wherein the message includes encrypted and non-encrypted data.

31. The card reader of claim 29, wherein the microcontroller includes countermeasures to detect tampering and attacks on the card reader.

32. The card reader of claim 29, wherein the card reader is configured to disable itself when modification or tampering is detected.

33. The card reader of claim 29, wherein the cryptographic key is expanded before programming, and wherein the microcontroller code does not include or require key expansion functionality.

34. The card reader of claim 29, wherein the microcontroller is configured to recalculate a bit period in real time to capture variable-speed swipes of the card in a slot of the card reader.

35. The card reader of claim 29, wherein the microcontroller is configured to parse and error-check card data.

36. The card reader of claim 29, wherein the microcontroller is configured to run periodic checksums on code and memory.

37. The card reader of claim 29, wherein the device electronics include an analog to digital front-end.

38. The card reader of claim 37, wherein the analog to digital front end is coupled to a processing element in the microcontroller, the analog to digital front end receiving the raw signal and converting the raw signal into a processed digital signal that the microcontroller can interpret.

39. The card reader of claim 37, wherein the analog to digital front end includes wake-up electronics.

40. The card reader of claim 29, wherein the output jack signal is a synchronous Manchester encoded stream or an asynchronized stream.

41. The card reader of claim 29, wherein the output jack signal is at a frequency such that the output jack signal appears as an AC to a microphone input of the mobile device.

42. The card reader of claim 29, wherein a frequency of the output jack signal is between 2 KHz and 48 kHz.

43. The card reader of claim 29, further comprising:

a power source coupled to wake-up electronics.

44. The card reader of claim 29, wherein the microphone bias voltage signal is used for powering the power subsystem of the card reader and for transmitting data from the card reader back to the mobile device.

45. The card reader of claim 29, wherein the microphone bias voltage signal is a direct current (DC) voltage signal, and wherein converting the microphone bias voltage signal into a system voltage signal comprises a DC to DC conversion.