Shared key encryption using long keypads

• US 20070076877A1
• Filed: 09/30/2005
• Published: 04/05/2007
• Est. Priority Date: 09/30/2005
• Status: Active Grant

• Current Assignee: Sony Ericsson Mobile Communications USA Incorporated (Sony Group Corp.)
• Original Assignee: Sony Ericsson Mobile Communications USA Incorporated (Sony Group Corp.)
• Inventors: Camp, William, Homiller, Daniel
• Granted Patent: US 8,050,405 B2
• Time in Patent Office: Days
• US Class Current: 380/255
• CPC Class Codes: H04L 2209/08 Randomization, e.g. dummy operations or using noise
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 63/0442 wherein the sending and receiving network entities apply asymmetric encryption, i.e. different keys for encryption and decryption cryptographic mechanisms or cryptographic arrangements for public-key encryption H04L9/30
• CPC Class Codes: H04L 63/0457 wherein the sending and receiving network entities apply dynamic encryption, e.g. stream encryption cryptographic mechanisms or cryptographic arrangements for stream encryption H04L9/065
• CPC Class Codes: H04L 9/065 Encryption by serially and continuously modifying data stream elements, e.g. stream cipher systems, RC4, SEAL or A5/3
• CPC Class Codes: H04L 9/0869 involving random numbers or seeds
• CPC Class Codes: H04L 9/3242 involving keyed hash functions, e.g. message authentication codes [MACs], CBC-MAC or HMAC
• CPC Class Codes: H04W 12/03 Protecting confidentiality, e.g. by encryption
• CPC Class Codes: H04W 12/041 Key generation or derivation
• CPC Class Codes: H04W 12/0471 Key exchange
• CPC Class Codes: H04W 12/106 Packet or message integrity
• CPC Class Codes: H04W 84/18 Self-organising networks, e.g. ad-hoc networks or sensor networks

Abstract

Methods of securely communicating a message from a first terminal to a second terminal include generating a keypad including a random sequence of bits having a length L, encrypting the message at the first terminal using a bit string beginning at an offset O in the keypad, and transmitting the encrypted message and an indicator of the offset O to the second terminal. A communication terminal includes a controller, a communication module configured to establish a location-limited communication channel, and an encryption unit configured to store a keypad including a random sequence of bits having a length L, to encrypt an outgoing message using the keypad, and to decrypt an incoming message using the keypad.

Claims

1. A method of securely communicating a message from a first terminal to a second terminal, comprising:

generating a keypad comprising a random sequence of bits having a length L;

encrypting the message at the first terminal using a bit string beginning at an offset O in the keypad; and

transmitting the encrypted message and an indicator of the offset O to the second terminal.

2. The method of claim 1, further comprising establishing a secure channel between the first terminal and the second terminal and transmitting the keypad from the first terminal to the second terminal over the secure channel.

3. The method of claim 2, wherein establishing a secure channel comprises establishing a location-limited channel between the first terminal and the second terminal.

4. The method of claim 3, wherein establishing a location-limited channel between the first terminal and the second terminal comprises establishing an infrared communication channel, a direct cable connection or a Bluetooth communication channel between the first terminal and the second terminal.

5. The method of claim 2, wherein establishing a secure channel comprises establishing a key-encrypted channel between the first terminal and the second terminal.

6. The method of claim 5, wherein establishing a key-encrypted channel between the first terminal and the second terminal comprises establishing a secret key encrypted communication channel between the first terminal and the second terminal using a secret key derived from a previously stored keypad.

7. The method of claim 5, wherein establishing a key-encrypted channel comprises establishing a public-key encrypted communication channel between the first terminal and the second terminal.

8. The method of claim 1, wherein encrypting the message at the first terminal comprises performing an EXCLUSIVE OR operation between bits in the message and the bit string in the keypad.

9. The method of claim 8, further comprising advancing an offset counter by a number equal to the number of bits used in the EXCLUSIVE OR operation.

10. The method of claim 1, wherein the indicator of the offset O is the offset O.

11. The method of claim 1, wherein the indicator of the offset O is an index number.

12. The method of claim 1, further comprising encrypting the indicator of the offset O and wherein transmitting the encrypted message and the indicator of the offset O comprises transmitting the encrypted message and the encrypted indicator of the offset O.

13. The method of claim 1, further comprising generating a key digest from the keypad and transmitting the key digest to the second terminal along with the encrypted message.

14. The method of claim 1, wherein generating the keypad comprises sampling a random noise source.

15. The method of claim 14, wherein the random noise source comprises a radio receiver tuned to a channel with no signal present.

16. The method of claim 15, further comprising:

filtering an output of the radio receiver with a filter having a frequency response that is inverse to the passband of the receiver to thereby generate a filtered noise signal; and

sampling the filtered noise signal.

17. The method of claim 1, further comprising:

increasing an offset counter after transmitting the encrypted message;

checking the offset counter to determine an amount of unused keypad; and

generating a new keypad responsive to the amount of unused keypad being less than a predetermined threshold value.

18. The method of claim 1, further comprising authenticating a user of the first terminal prior to generating a keypad.

19. The method of claim 1, further comprising associating the generated keypad with the first terminal and the second terminal.

20. The method of claim 1, wherein generating a keypad comprises generating a keypad at a key server and the method further comprises transmitting the keypad from the key server to the first and second terminals.

21. The method of claim 1, further comprising:

calculating verification data at the first terminal; and

transmitting the verification data along with the encrypted message to the second terminal.

22. The method of claim 21, wherein the verification data comprises a message authentication code, a CRC or a checksum.

23. The method of claim 1, wherein the length of the keypad is at least 1000 bits.

24. The method of claim 1, wherein the length of the keypad is at least 1,000,000 bits.

25. A communication terminal, comprising:

a controller;

a communication module operatively controlled by the controller and configured to establish a location-limited communication channel; and

an encryption unit operatively controlled by the controller and including an encryption memory configured to store a keypad, an encryptor configured to encrypt an outgoing message using the keypad, and a decryptor configured to decrypt an incoming message using the keypad.

26. The communication terminal of claim 25, wherein the terminal is configured to generate the keypad by sampling a random data source.

27. The communication terminal of claim 25, wherein the encryption memory is not addressable by the controller.

28. The communication terminal of claim 25, wherein the communication module is configured to establish an infrared connection, a Bluetooth connection and/or a direct cable connection with a second terminal.

29. A communication system, comprising:

a first terminal configured to generate a keypad comprising a random sequence of bits having a length L, to establish a secure channel, and to transmit the keypad over the secure channel; and

a second terminal configured to establish the secure channel with the first terminal and to receive the keypad over the secure channel, wherein the first terminal is further configured to encrypt a message using a bit string beginning at an offset O in the keypad, and to transmit the encrypted message and an indicator of the offset O to the second terminal over a physically insecure channel.

30. A method of securely communicating a message from a first terminal to a second terminal, comprising:

generating a key comprising a random sequence of bits by sampling a random noise source;

encrypting the message at the first terminal using the key; and

transmitting the encrypted message to the second terminal.

31. The method of claim 30, wherein the random noise source comprises a radio receiver tuned to a channel with no signal present.