Dynamic private key security system for personal messaging devices

• US 6,169,802 B1
• Filed: 12/17/1996
• Issued: 01/02/2001
• Est. Priority Date: 12/17/1996
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Lerner, Kenneth, Burgan, John
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US08/768,761
• Time in Patent Office: 1,477 Days
• Field of Search: 380/21, 380/49, 380/43, 380/44
• US Class Current: 380/44
• CPC Class Codes: H04L 2209/60 Digital content management, e.g. content distribution
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner

Abstract

A dynamic private key security system for personal messaging devices (200) includes a paging terminal (112). The paging terminal (112) has a terminal cryptographic engine (111) that generates an encrypted message using a terminal session key based on a first information content of a prior message, and generates a next message key based on a second information content of a current message. The terminal session key is used to encrypt the current message, and the next message key is used to encrypt a next message.

Claims

1. A dynamic private key security system for personal messaging devices, comprising a paging terminal, comprising:

a terminal cryptographic engine that generates an encrypted message using a terminal session key based on a first information content of a prior message transmitted by the paging terminal, and generates a next message key based on a second information content of a current message to be transmitted by the paging terminal, the terminal session key being used to encrypt the current message and the next message key being used to encrypt a next message.

2. The dynamic private key security system for personal messaging devices according to claim 1, wherein the paging terminal further comprises:

a telephone network input that accepts messaging requests from external sources.

3. The dynamic private key security system for personal messaging devices according to claim 1, wherein the dynamic private key security system further comprises a personal messaging device, comprising:

a messaging device cryptographic engine that decrypts the encrypted message as a current received decrypted message using a messaging device session key that is based on a third information content of a prior received decrypted message, the third information content of the prior received decrypted message being virtually identical to the first information content of the prior message, and the messaging device session key being identical to the terminal session key, the messaging device cryptographic engine further operating to generate a next messaging device session key based on a fourth information content of the current received decrypted message, the fourth information content being virtually identical to the second information content of the current message, and the next messaging device session key being used to decrypt a next received encrypted message.

4. The dynamic private key security system for personal messaging devices according to claim 3, wherein the personal messaging device further comprises:

a non-volatile memory coupled to the messaging device cryptographic engine for storing the messaging device session key and the next messaging device session key.

5. The dynamic private key security system for personal messaging devices according to claim 3, wherein the personal messaging device further comprises:

a processor; and

a decoder coupled to the processor, the decoder operating to detect and correct errors in the encrypted message creating a decoded message that is coupled to the messaging device cryptographic engine for decryption creating the current received decrypted message that is further coupled to the processor for message integrity testing.

6. The dynamic private key security system for personal messaging devices according to claim 5, wherein the personal messaging device further comprises:

a transmitter coupled to the processor, the transmitter operating to send an acknowledge back response to the paging terminal indicating whether or not the encrypted message has been correctly received, decoded, and decrypted.

7. The dynamic private key security system for personal messaging devices according to claim 1, wherein the paging terminal further comprises:

a key database coupled to the terminal cryptographic engine for storing the terminal session key and the next message key.

8. The dynamic private key security system for personal messaging devices according to claim 7, wherein the paging terminal further comprises:

a processor coupled to the terminal cryptographic engine.

9. The dynamic private key security system for personal messaging devices according to claim 8, wherein the paging terminal further comprises

a transmitter coupled to the processor, the transmitter operating under control of the processor to broadcast the encrypted message to selected personal messaging devices.

10. The dynamic private key security system for personal messaging devices according to claim 9, wherein the paging terminal further comprises:

a receiver coupled to the processor, the receiver operating under control of the processor to receive and decode acknowledge back responses from the selected personal messaging devices indicating whether or not the encrypted message broadcast to selected personal messaging devices were received, decoded, and decrypted without errors.

11. In a dynamic private key security system, a method for communicating secure messages comprising the steps of:

at a paging terminal;

generating an encrypted message from a current message using a terminal session key based on a first information content of a prior message transmitted by the paging terminal; and

generating a next message key based on a second information content of the current message to be transmitted by the paging terminal, the terminal session key being used to encrypt the current message and the next message key being used to encrypt a next message.

12. The method for communicating secure messages according to claim 11 further comprising the steps of:

at the paging terminal;

generating an initial key as the terminal session key and using the initial key as the terminal session key if the current message is a first message being sent after programming; and

programming the initial key as a messaging device session key in a non-volatile memory coupled to a messaging device cryptographic engine in a personal messaging device.

13. The method for communicating secure messages according to claim 12 further comprising the steps of:

at the paging terminal;

broadcasting the encrypted message for reception by the personal messaging device, the encrypted message being encrypted using one of the initial key, a terminal session key based on a first information content of a prior message, and a next message key based on a second information content of a current message, the terminal session key being used to encrypt the current message and the next message key being used to encrypt a next message.

14. The method for communicating secure messages according to claim 13 further comprising the steps of:

at the personal messaging device;

receiving the encrypted message;

decoding the encrypted message to detect and correct errors in the encrypted message and create a decoded message that is coupled to the messaging device cryptographic engine for decryption; and

decrypting the decoded message as a current received decrypted message using the messaging device session key based on one of the initial key and a third information content of a prior received decrypted message.

15. The method for communicating secure messages according to claim 14 further comprising the steps of:

at the personal messaging device;

generating a next messaging device session key based on a fourth information content of the current received decrypted message; and

saving the next messaging device session key in the non-volatile memory along with the messaging device session key.

16. The method for communicating secure messages according to claim 15 further comprising the steps of:

at the personal messaging device;

testing an integrity of the current received decrypted message by comparing a checksum within the current received decrypted message to a checksum calculated from a second information content of the current received decrypted message.

17. The method for communicating secure messages according to claim 16 further comprising the steps of:

at the personal messaging device;

acknowledging a correct reception, decoding and decryption of the encrypted message when the checksum within the current received decrypted message matches the checksum calculated from the second information content of the current received decrypted message.

18. The method for communicating secure messages according to claim 17 further comprising the steps of:

at the paging terminal;

receiving a positive acknowledgment from the personal messaging device;

generating a next encrypted message using the terminal session key set to the next message key; and

broadcasting the next encrypted message for reception by the personal messaging device.

19. The method for communicating secure messages according to claim 16 further comprising the steps of:

at the personal messaging device;

decrypting the decoded message as a second current received decrypted message using the next message key previously used to encrypt a last encrypted message received, decoded, decrypted, and acknowledged as being without errors when the checksum within the current received decrypted message did not match the checksum calculated from the second information content of the current received decrypted message.

20. The method for communicating secure messages according to claim 19 further comprising the steps of:

at the personal messaging device;

acknowledging an incorrect reception, decoding or decryption of the encrypted message when the checksum within the current received decrypted message did not match the checksum calculated from the second information content of the current received decrypted message.

21. The method for communicating secure messages according to claim 20 further comprising the steps of:

at the personal messaging device;

maintaining the messaging device session key at one of the initial key and the next messaging device session key based on a first information content of a prior message that is identical to the third information content of a prior received decrypted message when the checksum within the current received decrypted message did not match the checksum calculated from the second information content corresponding with the current received decrypted message and the checksum within the second current received decrypted message did not match the checksum calculated from the second current received decrypted message.

22. The method for communicating secure messages according to claim 21 further comprising the steps of:

at the paging terminal;

receiving a negative acknowledgment from the personal messaging device;

regenerating the encrypted message using the terminal session key set to the next message key previously used to encrypt the last encrypted message received, decoded, decrypted, and acknowledged as being without errors; and

rebroadcasting the encrypted message for reception by the personal messaging device.