TIME OF DAY ENCRYPTION USING TDMA TIMING

• US 20090323952A1
• Filed: 05/27/2009
• Published: 12/31/2009
• Est. Priority Date: 05/27/2008
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Smith, Edward Frank
• Granted Patent: US 8,165,296 B2
• Time in Patent Office: Days
• US Class Current: 380/255
• CPC Class Codes: H04B 7/18589 Arrangements for controlling an end to end session, i.e. for initialising, synchronising or terminating an end to end link

Abstract

Embodiments of the invention provide for encryption and decryption of data in a TDMA network using TDMA time values. In some embodiments, TDMA time values can be transmitted to terminals from a network controller using a burst time plan. These TDMA time values along with other data and/or counters can be combined to create a one-time key, which can be used to both encrypt data and/or decrypt data. Embodiments of the invention can decrease communication overhead by using the TDMA time value for TDMA purposes as well as for encryption purposes.

Claims

1. A method for encrypting data in a TDMA communication system at a transmitting terminal, the method comprising:

receiving a transmit TDMA timeslot assignment, with a TDMA time value, from a TDMA controller;

receiving data from a user;

calculating a one-time key-stream from at least the TDMA time value using a controller;

encrypting the data using the one-time key-stream to produce encrypted data with the controller; and

transmitting the encrypted data to a receiver.

2. The method according to claim 1, wherein the TDMA communication system comprises a multi-frequency TDMA communication system.

3. The method according to claim 1, wherein the one-time key-stream is calculated from a plurality of counter values.

4. The method according to claim 1, wherein the calculating a one-time key-stream comprises:

creating a counter value from the TDMA time value; and

calculating a one-time key-stream from the counter value using a block encryption function.

5. The method according to claim 4, wherein the counter value is created by combining the TDMA time value with one or more values selected from the group consisting of a transmission frequency representation, a system parameter, a block counter value, and a terminal parameter.

6. The method according to claim 1, wherein a subsequent counter value is created by incrementing the previous counter value.

7. The method according to claim 1, wherein the encrypting the data using the one-time key-stream further comprises creating the encrypted value using an exclusive disjunction function.

8. A method for decrypting data in a TDMA communication system at a TDMA controller, the method comprising:

receiving a receive TDMA timeslot assignment that includes a TDMA time value, from a TDMA controller;

receiving data from a transmitting terminal;

calculating a one-time key-stream from at least a TDMA time value using a controller;

decrypting, with the controller the encrypted data using the one-time key-stream producing decrypted data; and

transmitting the decrypted data to a user.

9. The method according to claim 8, wherein the one-time key-stream is calculated by encrypting the TDMA time value

10. The method according to claim 8, wherein the one-time key-stream is calculated by encrypting a plurality of counter values.

11. The method according to claim 8, wherein the one-time key-stream is calculated using the TDMA time value and at least one value selected from the group consisting of;

a transmission frequency representation, a system parameter, and a terminal parameter.

12. The method according to claim 9, wherein a subsequent counter value is created by incrementing a previous counter value.

13. The method according to claim 8, wherein decrypting the data using the one-time key-stream further comprises creating the decrypted value using an exclusive disjunction function.

14. A method for decrypting data in a communication network, the method comprising:

transmitting a burst time plan to both the transmitting and the receiving terminals within a network of terminals, the burst time plan including at least a TDMA time value and specifying a timeslot within which the transmitting terminal should transmit data;

receiving encrypted data from the transmitting terminal within the timeslot specified by the burst time plan;

creating a counter value from at least the TDMA time value using a controller calculating a one-time key-stream from the counter value using the controller; and

decrypting, with the controller, the encrypted data using the one-time key-stream.

15. The method according to claim 14, wherein consecutive counter values are incremented.

16. The method according to claim 14, wherein the counter value is created using a value selected from the group consisting of a transmission frequency representation, a system parameter, and a terminal parameter.

17. The method according to claim 14, wherein the one-time key stream is calculated from the counter value using a one-way function.

18. The method according to claim 14, wherein the one-time key stream is calculated from the counter value using a block encryption function.

19. The method according to claim 14, wherein the decrypting the encrypted data using the one-time key-value includes using an exclusive disjunction function.

20. A method for encrypting data in a communication network, the method comprising:

receiving a TDMA time value;

receiving data from a source distinct from the source of the TDMA time value;

calculating, with a controller, a one-time key-value from at least the TDMA time value;

encrypting the data, with the controller, using the one-time key-value; and

transmitting the encrypted data.

21. The method according to claim 20, wherein the one-time key-value includes at least one value selected from the group of values consisting of a system identification value, a terminal identification value, and a carrier frequency value.

22. A communication modem comprising:

a user port configured to receive data from a user;

a network port;

a controller communicatively coupled with the user port and the network communications port; and

memory communicatively coupled with the controller, the memory including instructions executable by the processor, wherein the instructions include;

instructions to receive user data through the user port;

instructions to receive a burst time plan and store at least portions of the burst time plan in memory, wherein the burst time plan includes a global time value;

instructions to calculate a one-time key-value from the global time value;

instructions to encrypt the user data with the one-time key-value; and

instructions to send the encrypted user data to the communications network using the network communications port.

23. The communication modem according to claim 22, wherein the burst time plan includes an indication specifying a timeslot within which the communication modem should transmit the encrypted user data.

24. The communication modem according to claim 22, wherein the instructions to calculate a one-time key-value from the global time value include instructions to calculate a one-time key-value from the global time value using a one-way function.