METHOD FOR TRANSFERRING AN ENCRYPTION KEY

• US 20010055395A1
• Filed: 03/02/1998
• Published: 12/27/2001
• Est. Priority Date: 03/02/1998
• Status: Active Grant

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: VOGLER, DEAN H.
• Granted Patent: US 6,393,127 B2
• Time in Patent Office: Days
• US Class Current: 380/273
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying

Abstract

Encryption keys are transferred by obtaining a public and private key pair (42, 65) from a source device (21, 61). The public key is transmitted (42, 65) from the source device (43, 66) to a target device (23, 62). The target (23, 62) obtains a traffic key (44, 67) stored within the target device (23, 62). The traffic key is encrypted (45, 68) within the target device using the public key. The encrypted traffic key is transmitted to the source device (46, 69) where it is decrypted (47, 70) using the private key. The replacement encryption key(s) is(are) encrypted using the traffic key by the source device (48, 71) forming an encrypted replacement key message which contains a target slot identification for each of the replacement encryption keys. The encrypted replacement key message is transmitted to the target device (49, 72) where the replacement encryption key(s) is(are) recovered (50, 73). The replacement encryption key(s) is(are) then stored at the target device in an identified target slot (51). The public, private, and traffic keys may then be erased from the source and target devices as appropriate.

Claims

1. A method for transferring a replacement encryption key, said method comprising the steps of:

transmitting a public key from a source device to a target device;

encrypting a traffic key within said target device using said public key thereby forming a requested key;

transmitting said requested key to said source device;

encrypting said replacement encryption key using said traffic key at said source device forming an encrypted replacement key;

transmitting said encrypted replacement key to said target device; and

recovering said replacement encryption key.

2. The method of

claim 1

wherein said method further comprises the step of generating said public key and a private key in said source device.

3. The method of

claim 2

wherein said public key and said private key are generated using a data set.

4. The method of

claim 3

wherein said data set comprises at least a portion of one of a key stroke file, a real time clock, and an output from a linear feedback shift register.

5. The method of

claim 2

wherein said method further comprises the step of decrypting said requested key using said private key at said source device.

6. The method of

claim 1

wherein said method further comprises the step of selecting said traffic key from within said target device.

7. The method of

claim 1

wherein said method further comprises the step of receiving said encrypted replacement key at said target device.

8. The method of

claim 1

wherein said method further comprises the step of storing said replacement encryption key at said target device.

9. The method of

claim 1

wherein said step of transmitting said public key transmits said public key using at least one of a wired connection, a radio frequency connection, and an infrared connection.

10. The method of

claim 1

wherein said step of transmitting said public key comprises the step of transmitting said public key in a message.

11. The method of

claim 10

wherein said step of transmitting said requested key comprises the step of transmitting said requested key in a message.

12. The method of

claim 11

wherein said message further comprises a key slot within said target device to be used to identify a location for storage of said replacement encryption key.

13. The method of

claim 2

wherein said method further comprises the step of acknowledging receipt of said encrypted replacement key by said target device.

14. The method of

claim 13

wherein said method further comprises the steps of:

erasing said traffic key from said source device; and

erasing said public key and said private key from said source device.

15. A method for transferring a replacement encryption key, said method comprising the steps of:

obtaining a public key and a private key from a source device;

transmitting said public key from said source device to a target device;

obtaining a traffic key from within said target device;

encrypting a traffic key within said target device using said public key thereby forming a requested key;

transmitting said requested key to said source device;

decrypting said requested key using said private key at said source device;

encrypting said replacement encryption key using said traffic key at said source device forming an encrypted replacement key;

transmitting said encrypted replacement key to said target device;

recovering said replacement encryption key; and

storing said replacement encryption key at said target device.

16. The method of

claim 15

wherein the step of obtaining said traffic key comprises one of selecting an existing traffic key and generating said traffic key.

17. The method of

claim 15

wherein the step of transmitting said encrypted replacement key comprises a message identifying at least one replacement key and a storage location for each replacement encryption key.

18. The method of

claim 15

wherein the step of recovering said replacement encryption key comprises the step of decrypting said encrypted replacement key at said target device using said traffic key.

19. The method of

claim 15

further comprising the steps of:

acknowledging receipt of said encrypted replacement key by said target device;

erasing said traffic key from said source device and said target device; and

erasing said public key and said private key from said source device.

20. A method for transferring a plurality of replacement encryption keys, said method comprising the steps of:

obtaining a public key and a private key from a source device;

transmitting said public key from said source device to a target device;

obtaining a traffic key from within said target device;

encrypting a traffic key within said target device using said public key thereby forming a requested key;

transmitting said requested key to said source device;

decrypting said requested key using said private key at said source device;

encrypting said plurality of replacement encryption keys using said traffic key at said source device forming an encrypted replacement key message which further contains a target slot identification for each of said plurality of replacement encryption keys;

transmitting said encrypted replacement key message to said target device;

recovering said plurality of replacement encryption keys from said encrypted replacement key message; and

storing said plurality of replacement encryption keys at said target device in a target slot identified for each of said plurality of replacement encryption keys.