Method for the protected transmission of data, particularly transmission over an air interface

• US 20050229084A1
• Filed: 03/23/2005
• Published: 10/13/2005
• Est. Priority Date: 09/23/2002
• Status: Active Grant

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Cuylen, Michael
• Granted Patent: US 7,676,723 B2
• Time in Patent Office: Days
• US Class Current: 714/776
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04L 1/16 in which the return channel carries supervisory signals, e.g. repetition request signals

Abstract

The method relates to the protected transmission of data (D0-D4), the coding (‘S,’ ‘0’-‘F’) of which is represented, respectively, by a sequence (FR0-FR4) of a predefined number of on and off values (Z1, Z0). A count value (C) representing the predefined number is formed by changing the count direction (F, R) after each on value and incrementing or decrementing the count value with each off value. An error information (F1, F2) is generated if a first end value (EC), which is transmitted together with the data as a coded sequence (SIG) of the count value C, differs from a second end value (EC1, EC2), which, like the count value, is formed from the transmitted sequence. The method is advantageously used in identification systems (IS), in mobile data carriers (DT) and in read-write devices (SLG). This affords the advantage that a data transmission error can be detected quickly and with high reliability by using a simple forward and backward counter (CNT). The counter can be implemented with little circuit complexity by a simple software program or by an electronic circuit, e.g., by a binary cycle counter.

Claims

1. Method for protected transmission of data packets, the method comprising:

a) dividing at least one of the data packets into a sequence of data blocks, dividing at least one of the data blocks into a sequence of data, wherein a coding for each data in said sequence of data is represented by a sequence of a predefined number of on and off values,

b) forming a protection datum from the sequence of data and a protection block from the sequence of data blocks,

c) generating a first data request if the protection datum transmitted together with the data differs from a protection datum formed in a same manner upon receipt of at least one data block, and

d) generating a second data request if the protection block transmitted together with the data blocks differs from a protection block formed in a same manner upon receipt of at least one data packet.

2. Method as claimed in claim 1, wherein the sequence of data is followed by a first pause block, and the sequence data blocks are followed by a second pause block.

3. Method as claimed in claim 1, wherein the protection datum is coded in the same manner as a datum in the sequence of data.

4. Method as claimed in claim 1, wherein a protection block is formed in a same manner as the sequence of data using protection block data.

5. Method as claimed in claim 1, wherein the first data request is coded as a first data repeat sequence of a predefined number of on and off values in the first pause block.

6. Method as claimed in claim 1, wherein the second data request is coded as a second data repeat sequence of a predefined number of on and off values in the second pause block.

7. Method as claimed in claim 5, wherein the first data repeat sequence differs from the sequence of the predefined number of on and off values.

8. Method as claimed in claim 6, wherein the second data repeat sequence differs from the sequence of the predefined number of on and off values.

9. Method of claim 1, wherein the protection datum is formed using a procedure comprising:

maintaining a count of the sequence of the predefined number of on and off vales;

changing a count direction with each on value; and

incrementing or decrementing the count based on said count direction with each off value.

10. Method of claim 9, wherein the count moves cyclically within a hexadecimal range of values O-F.

11. A mobile data memory for the contactless exchange of protected data packets with a read-write device, having a first coding device, the first coding device comprising:

a first comparer operable to generate a first data request if a protection datum received together with data in the data packet differs from a protection datum formed in a same manner,

a second comparer operable to generate a second data request if a protection block of the data packet received together with data blocks differs from a protection block formed in a same manner,

a first querier operable to repeat previously transmitted data after detection of a first data request, and

a second querier operable to repeat previously transmitted data blocks after detection of a second data request.

12. A read-write device for the contactless exchange of protected data packets with a second mobile data memory, having a second coding device, the second coding device comprising:

a third comparer operable to generate a first data request if a protection datum received together with data of the data packet differs from a protection datum formed in a same manner,

a fourth comparer operable to generate a second data request if the protection block of the data packet received together with data blocks differs from a protection block formed in a same manner,

a third querier, operable to repeat previously transmitted data after detection of a first data request, and

a fourth querier, operable to repeat previously transmitted data blocks after detection of a second data request.

13. An identification system comprising:

a mobile data memory for the contactless exchange of protected data packets with a read-write device, having a first coding device, and

a read-write device for the contactless exchange of protected data packets with a second mobile data memory, having a second coding device,

the first coding device further comprising;

a first comparer operable to generate a first data request if a protection datum received together with data in the data packet differs from a protection datum formed in a same manner,

a second comparer operable to generate a second data request if a protection block of the data packet received together with data blocks differs from a protection block formed in a same manner,

a first querier operable to repeat previously transmitted data after detection of a first data request, and

a second querier operable to repeat previously transmitted data blocks after detection of a second data request,

the second coding device further comprising;

a third comparer operable to generate a first data request if a protection datum received together with data of the data packet differs from a protection datum formed in a same manner,

a fourth comparer operable to generate a second data request if the protection block of the data packet received together with data blocks differs from a protection block formed in a same manner,

a third querier, operable to repeat previously transmitted data after detection of a first data request, and

a fourth querier, operable to repeat previously transmitted data blocks after detection of a second data request,

wherein the read-write device and the data memory are together operable to exchange data packets via a contactless data transmission link.

14. The identification system of claim 13 wherein the exchange of data is based on ISO/IEC Standard 14443 for operation in an ISM frequency band.

15. The identification system of claim 13 wherein the exchange of data is based on ISO/IEC Standard 15693 for operation in an ISM frequency band.

16. The identification system of claim 14, wherein the ISM frequency band is of a wavelength of 13.56 MHz.

17. The identification system of claim 15, wherein the ISM frequency band is of a wavelength of 13.56 MHz.