System and method for securely adding redundancy to an electronic message

• US 20060123313A1
• Filed: 02/17/2005
• Published: 06/08/2006
• Est. Priority Date: 11/22/2004
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: Blackberry Limited
• Inventors: Brown, Michael S., Brown, Michael K., Kirkup, Michael G.
• Granted Patent: US 7,533,331 B2
• Time in Patent Office: Days
• US Class Current: 714/758
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control

Abstract

A system for adding a redundancy check to an electronic message to discourage tampering and facilitate identification of altered messages provides a communication device for composing message content, a messaging module with a formatting and encoding layer for encoding the message content with header information in a series of message blocks, and an encryption layer for calculating a redundancy check value and inserting the value in one or more locations within the series of message blocks according a rule defined by a characteristic of the message content or the header information, and encrypting the message for delivery to a recipient. Upon receipt, the recipient communication device decrypts the message, extracts the redundancy check value from the message, and compares a calculated redundancy check value with the extracted redundancy check value to determine if the message had been altered before receipt.

Claims

1. A method for a sending communication device to provide redundancy to an electronic message to be sent to a recipient communication device, the method comprising the steps of

determining a redundancy value for the electronic message to be sent,

determining a locating value, the locating value being defined such that the value varies for different electronic messages and being defined such that the locating value may be determined by the recipient communication device for each electronic message sent to it,

placing the redundancy value in the electronic message at one or more locations determined by the locating value,

encrypting the electronic message including the redundancy value

2. The method of claim 1 further comprising, prior to the step of placing the redundancy value in the electronic message at one or more locations determined by the locating value, the step of:

formatting the electronic message as a series of message blocks, and formatting the redundancy value as one or more redundancy value blocks.

3. The method of claim 1 wherein the step of determining a locating value comprises the step of determining the value of a characteristic of the electronic message.

4. The method of claim 3 wherein the step of encrypting the electronic message including the redundancy value comprises the step of assigning a session key to the electronic message.

5. The method of claim 4 wherein the step of determining the value of a characteristic of the electronic message comprises the step of determining the number of bits of a predetermined value in the session key.

6. The method of claim 5 wherein the step of determining the value of a characteristic of the electronic message further comprises the step of determining the parity of the number of bits.

7. The method of claim 2 wherein the step of placing the redundancy value in the electronic message at one or more locations determined by the locating value comprises the steps of selecting a message block from the series of message blocks based on the locating value, and inserting at least one of the one or more redundancy value blocks in a location defined in relation to the selected message block.

8. The method of claim 2 wherein the step of determining a locating value comprises the step of determining the value of a characteristic of one or more predetermined message blocks.

9. A communication device for sending a message to a recipient communication device, comprising:

program code operative to define a message;

program code operative to determine a redundancy value for the message;

program code operative to determine a locating value, the locating value being defined such that the value varies for different messages and being defined such that the locating value may be determined by the recipient communication device for each message sent to it;

program code operative to place the redundancy value in the message at one or more locations determined by the locating value; and

program code operative to encrypt the message including the redundancy value.

10. The communication device of claim 9 wherein the locating value is the value of a selected characteristic of the message.

11. The communication device of claim 10 wherein the program code operative to encrypt the message including the redundancy value is operative to encrypt the message using a session key.

12. The communication device of claim 11 wherein the selected characteristic of the message is the number of bits of a predetermined value in the session key.

13. The communication device of claim 11 wherein the selected characteristic of the message is the parity of the number of bits of a predetermined value in the session key.

14. The communication device of claim 9 further comprising:

program code operative to format the message as a series of message blocks; and

program code operative to format the redundancy value as one or more redundancy value blocks,

such that the program code operative to place the redundancy value in the message at one or more locations determined by the locating value is operative to identify one of the series of message blocks, and then insert at least one of the one or more redundancy value blocks in a location defined in relation to the identified one of the series of message blocks.

15. The communication device of claim 14 wherein the program code operative to encrypt the message including the redundancy value is operative to encrypt the message using a session key.

16. The communication device of claim 15 wherein the locating value is the number of bits of a predetermined value in the session key.

17. The communication device of claim 15 wherein the locating value is the parity of the number of bits of a predetermined value in the session key.

18. The communication device of claim 14, further comprising:

program code operative to derive a value from a characteristic of a specified block in the series of message blocks as the locating value;

program code operative to locate an identified message block based on the locating value; and

program code operative to insert at least one of the one or more redundancy value blocks in a location defined in relation to the identified message block.

19. The communication device of claim 18 wherein the characteristic of a specified block is the number of bits of a predetermined value in the specified block.

20. The communication device of claim 18 wherein the characteristic of a specified block is the parity of the number of bits of a predetermined value in the specified block.

21. A communication device for decrypting an encrypted message, the message comprising a plurality of message blocks and one or more redundancy value blocks placed among the plurality of message blocks according to a locating value, the locating value being defined such that the locating value varies for different messages, the communication device comprising:

program code operative to decrypt the encrypted message;

program code operative to locate the one or more redundancy value blocks in the message based on the locating value;

program code operative to obtain a received redundancy value from the one or more redundancy value blocks;

program code operative to determine a calculated redundancy value from the plurality of message blocks;

program code operative to compare the received redundancy value with the calculated redundancy value.

22. The communication device of claim 21 wherein the program code operative to locate the one or more redundancy value blocks in the message based on the locating value comprises:

program code operative to determine or receive the locating value;

program code operative to identify one of the plurality of message blocks using the locating value; and

program code operative to identify the location of at least one of the one or more redundancy value blocks in relation to the location of the identified one of the plurality of message blocks within the message.

23. The communication device of claim 22 wherein the locating value is a session key provided with the encrypted message.

24. A method for determining the reliability of a received encrypted message, the message comprising a plurality of message blocks and one or more redundancy value blocks placed among the plurality of message blocks according to a locating value, the locating value being defined such that the locating value varies for different messages, the method comprising the steps of:

decrypting the encrypted message to obtain a message;

locating the one or more redundancy value blocks in the message based on the locating value;

obtaining a received redundancy value from the one or more redundancy value blocks;

determining a calculated redundancy value from the plurality of message blocks;

comparing the received redundancy value with the calculated redundancy value; and

determining that the message is not reliable if the received redundancy value and the calculated redundancy check value are not equal.

25. The method of claim 24 further comprising the steps of:

identifying one of the plurality of message blocks using the locating value; and

identifying the location of at least one of the one or more redundancy value blocks in relation to the location of the identified one of the plurality of message blocks within the message.

26. A communication device for sending a message to a recipient device over a network, comprising:

a processor;

a memory;

an interface to allow input of a message;

a network connection;

a messaging module operably connected with the processor and the memory to receive message input using the interface, the messaging module being configured to;

format the message as a series of message blocks,

calculate a redundancy value from the message and format the redundancy value into at least one redundancy value block,

determine a locating value such that the locating value varies for different messages and may be determined by the recipient device for each message sent to it,

placing the at least one redundancy value block in the series of message blocks according to a predetermined rule based on the locating value, and

encrypt the message blocks and the at least one redundancy value block placed therein to provide an encrypted message, and

transmit the encrypted message over the network connection.