Crypto-synchronization for secure communication

• US 7,715,559 B2
• Filed: 08/26/2004
• Issued: 05/11/2010
• Est. Priority Date: 08/26/2004
• Status: Active Grant

• Current Assignee: Motorola Solutions, Inc.
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Rainbolt, Bradley J., Boillot, Marc A.
• Primary Examiner(s): Orgad; Edan
• Assistant Examiner(s): Baum; Ronald
• Application Number:
  US10/926,830
• Publication Number:
  US 20060045136A1
• Time in Patent Office: 2,084 Days
• Field of Search: 380/225
• US Class Current: 380/225
• CPC Class Codes: H04K 1/00 Secret communication
• CPC Class Codes: H04L 1/0041 Arrangements at the transmitter end
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner

Abstract

An apparatus (213) and corresponding methods (FIG. 7) to facilitate maintaining crypto synchronization while processing communication signals in a communication unit includes a vocoder (215) configured to convert input audio band signals to vocoder output frames; a crypto processor (217) configured to encrypt the vocoder output frames to provide encrypted output frames; and a synchronizer (219) configured to substitute in a predetermined manner synchronization information corresponding to an encryption state of the crypto processor for a portion of the encrypted data in a portion of the encrypted output frames to provide resultant output synchronization frames suitable for synchronizing a decryption process at a target communication unit.

Claims

1. A method of facilitating crypto synchronization for secure communication, the method comprising:

encrypting communication data using an encrypting process to provide encrypted communication data;

providing synchronization information to synchronize a decrypting process at a target communication unit;

substituting in a predetermined manner the synchronization information for a portion of the encrypted communication data to provide resultant data to send to the target communication unit;

determining that resultant data contains synchronization information at the target communication unit

during speech reconstruction at the target communication unit, ignoring the synchronization information and processing the encrypted communication data such that the target communication unit does not use or execute the synchronization information during the speech reconstruction, wherein the synchronization information is ignored by processing only a portion of the resultant data within a frame less a portion of the frame having the synchronization information.

2. The method of claim 1 further comprising generating the communication data using a vocoder, wherein the communication data further comprises a vocoder frame.

3. The method of claim 2 wherein the substituting in a predetermined manner further comprises inserting the synchronization information into the vocoder frame in lieu of a portion of the vocoder frame.

4. The method of claim 3 wherein the vocoder frame further comprises a series of vocoder frames and the inserting the synchronization information further comprises inserting the synchronization information in a predetermined portion of the series of vocoder frames.

5. The method of claim 1 wherein the providing synchronization information further comprises providing synchronization information corresponding to a state of the encryption process.

6. The method of claim 5 wherein the providing synchronization information further comprises providing information for detecting the synchronization information at the target communication unit.

7. The method of claim 1 further comprising:

providing a series of vocoder data frames from a vocoder;

wherein the encrypting further comprises encrypting the series of vocoder data frames with the encrypting process;

wherein the providing synchronization information comprises providing information corresponding to state information for the encryption process and a check sum corresponding to the state information, the state information changing as a function of a location of a vocoder data frame within the series of vocoder data frames; and

wherein the substituting in a predetermined manner comprises inserting in each of a predetermined portion of the vocoder data frames the state information and the check sum corresponding to each of the predetermined portion of the vocoder data frames.

8. A method of facilitating crypto synchronization for secure communication, the method comprising;

obtaining a frame of communication data;

determining whether a portion of the frame includes synchronization information that was substituted in a predetermined manner for a portion of encrypted communication data;

when the frame includes synchronization information using the synchronization information to update a decryption process, thereby facilitating the crypto synchronization; and

when the frame includes synchronization information, only the frame less the portion of the frame that includes the synchronization information is further processed during reconstruction of the frame such that a target communication unit does not use or execute the synchronization information during the frame reconstruction.

9. The method of claim 8 wherein the determining whether a portion of the frame includes synchronization information further comprises:

parsing the frame of communication data into a first part and a second part;

calculating a check sum corresponding to the first part and comparing the check sum to an embedded check sum within the frame of communication data; and

only when the check sum matches the embedded check sum deciding that the first part of the frame of communication data includes the synchronization information.

10. The method of claim 8 wherein the synchronization information further comprises state information corresponding to a state machine used in the decryption process.

11. The method of claim 8 wherein:

the frame of communication data is decrypted using the decryption process, the decryption process using a state machine; and

when the frame includes synchronization information, the synchronization information is used to update the state machine.

12. An apparatus arranged and constructed to facilitate maintaining crypto synchronization while processing communication signals, the apparatus comprising:

a vocoder configured to convert vocoder input frames to output audio band signals;

a crypto processor coupled to the vocoder and configured to decrypt input frames to provide the vocoder input frames; and

a synchronizer coupled to the crypto processor and configured to determine whether an input frame includes corresponding synchronization information;

wherein when the synchronizer determines that an input frame includes synchronization information, the vocoder ignores the synchronization information during the conversion of input frames to output audio band signals such that the vocoder does not use or execute the synchronization information of the input frame during the conversion of the input frames to output audio band signals.

13. The apparatus of claim 12 wherein:

the vocoder is further configured to convert input audio band signals to vocoder output frames;

the crypto processor is further configured to encrypt the vocoder output frames to provide encrypted output frames; and

the synchronizer is further configured to substitute in a predetermined manner synchronization information corresponding to an encryption state of the crypto processor for a portion of the encrypted data in a portion of the encrypted output frames to provide resultant output synchronization frames.

14. The apparatus of claim 13 wherein the crypto processor includes a state counter and the synchronizer generates the synchronization information by obtaining a value corresponding to the state counter contents and appending a check sum to this value to provide the synchronization information corresponding to each one of the portion of the encrypted output frames.

15. The apparatus of claim 13 wherein the synchronization information is substituted for the portion of the encrypted data where the portion is selected in view of audio quality of resultant output audio band signals.

16. The apparatus of claim 12 wherein the synchronizer is further configured to facilitate:

parsing the input frame into a first part and a second part;

calculating a check sum corresponding to the first part and comparing the check sum to an embedded check sum within the input frame; and

only when the check sum matches the embedded check sum deciding that the first part of the input frame includes the corresponding synchronization information.

17. The apparatus of claim 12 wherein when the input frame includes synchronization information, the synchronizer updates a state of the crypto processor using the synchronization information.

18. The apparatus of claim 12 wherein the vocoder is an AMBE+2 vocoder and the crypto processor;

encrypts vocoder output frames by forming an exclusive OR product of each bit in a vocoder output frame with an encryption bit in an encryption vector, the encryption vector varying with each vocoder output frame, and

decrypts the input frames by forming an exclusive OR product of each bit in an input frame with a decryption bit in a decryption vector, the decryption vector varying with each input frame.

19. The apparatus of claim 12 utilized in a communication unit.