Method and system for data integrity protection

• US 20040123102A1
• Filed: 10/24/2003
• Published: 06/24/2004
• Est. Priority Date: 05/03/2001
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Blom, Rolf, Gehrmann, Christian
• Granted Patent: US 7,298,840 B2
• Time in Patent Office: Days
• US Class Current: 713/161
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 9/3242 involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC

Abstract

A method of authenticating a message (111) received via a transmission channel (108) using a Message Authentication Code (MAC). The message comprises a message body (114) and a tag (116) and the method comprises the steps of generating a second tag (115) according to a MAC function (112) on the basis of the received message body and a secret key (113), calculating a distance (117) between the received tag and generated second tag, and comparing (118) the calculated distance with a predetermined threshold value

Claims

1. A method of authenticating data, the method comprising the steps of

receiving a message (114, 203) and a corresponding first data item (116, 213) generated according to a first predetermined rule (102, 206);

generating a second data item (115, 210) according to a second predetermined rule (112, 206) on the basis of the received message;

calculating a first distance (117, 215) between the received first data item and the generated second data item;

comparing the calculated first distance with a predetermined distance value (212).

2. A method according to claim 1, characterised in that the method further comprises the step of processing the message conditioned on a result of the step of comparing the calculated first distance with a predetermined distance value.

3. A method according to claim 1 or 2, characterised in that the step of processing the message comprises the step of accepting the message if the calculated first distance is smaller than the predetermined distance value.

4. A method according to any one of claims 1 through 3, characterised in that the message and the first data item are received via a wireless communications channel.

5. A method according to any one of claims 1 through 4, characterised in that the step of generating the second data item comprises the step of applying a predetermined permutation to a third data item derived from the message.

6. A method according to any one of claims 1 through 5, characterised in that the step of generating the second data item comprises the step of combining a fourth data item derived from the message with a predetermined fifth data item.

7. A method according to claim 6, characterised in that the step of combining a fourth data item derived from the message with a predetermined fifth data item comprises the step of inserting predetermined binary sequences at predetermined positions of the fourth data item.

8. A method according to any one of claims 1 through 7, characterised in that the step of calculating a first distance comprises the step of calculating a Hamming distance.

9. A method according to any one of claims 1 through 8, characterised in that the method further comprises the steps of

a) generating a first sequence of message sections from the message, each message section having a predetermined length;

b) modifying at least a first message section of the sequence of message sections;

c) applying at least a first permutation to at least the modified first message section of the sequence of message sections;

d) calculating at least one XOR sum of a result of at least the first permutation;

e) calculating a hash value from the calculated at least one XOR sum.

10. A method according to claim 9, characterised in that the method further comprises the step of repeating the steps of applying at least the first permutation and calculating an XOR sum a predetermined number of times.

11. A method according to claim 9 or 10, characterised in that the method further comprises the step of repeating the steps a) through e) using at least a second permutation.

12. A method according to any one of claims 9 through 11, characterised in that the method further comprises the step of encrypting the calculated hash value.

13. A method according to any one of claims 1 through 12, characterised in that the step of calculating the first distance further comprises the steps of

dividing the first and second data items into corresponding first and second sets of data sections;

calculating a second distance between a first section of the first set of sections and a corresponding second section of the second set of sections; and

comparing the second distance with a predetermined threshold value.

14. A method according to any one of claims 1 through 13, characterised in that the first data item is further generated on the basis of a first secret key code;

and the step of generating the second data item on the basis of the received message further comprises the step of generating the second data item on the basis of a second secret key code.

15. A method according to any one of claims 1 through 14, characterised in that the first and second secret key codes are the same key code;

and the first and second predetermined rules are the same rule.

22. A data signal embodied in a carrier wave for use in a method according to any one of the claims 1 through 15, the data signal comprising a message and a first data item.

23. A computer program comprising program code means for performing all the steps of any one of the claims 1 through 15 when said program is run on a microprocessor.

24. A computer program product comprising program code means stored on a computer readable medium for performing the method of any one of the claims 1 through 15 when said computer program product is run on a microprocessor.

16. A method of transmitting a message from a transmitter (101, 501) to a receiver (110, 506) via a transmission channel (108, 505), the method comprising the steps of

at the transmitter generating a first data item (105, 209) according to a first predetermined rule (102, 206) on the basis of the message (104, 202);

transmitting the message and the generated first data item from the transmitter to the receiver;

generating a second data item (115, 210) according to a second predetermined rule (112, 206) on the basis of the received message (114, 203);

calculating a first distance (215) between the received first data item (116, 213) and the generated second data item;

comparing the calculated first distance with a predetermined distance value (212).

17. A method according to claim 16, characterised in that the generated first data item has a size which is smaller than a size of the message.

18. A method according to claim 16 or 17, characterised in that the step of generating the first data item comprises the step of calculating a hash function on the basis of a sixth data item derived from the message.

19. A communications system comprising

first processing means (503) adapted to calculate a first data item according to a first predetermined rule on the basis of a message;

a transmitter (504) adapted to transmit the message and the generated first data item via a transmission channel (505);

a receiver (509) adapted to receive the transmitted message and the transmitted first data item;

second processing means (508) adapted to

generate a second data item according to a second predetermined rule on the basis of the received message;

to calculate a first distance between the received first data item and the generated second data item; and

to compare the calculated first distance with a predetermined distance value.

20. An apparatus comprising

a receiver (509) adapted to receive a message and a corresponding first data item generated according to a first predetermined rule;

first processing means (508) adapted to

generate a second data item according to a second predetermined rule on the basis of the received message;

to calculate a first distance between the received first data item and the generated second data item; and

to compare the calculated first distance with a predetermined distance value.

21. An apparatus according to claim 20, characterised in that the apparatus is a mobile radio terminal.