System for seamlessly updating service keys with automatic recovery

• US 20020146132A1
• Filed: 04/05/2002
• Published: 10/10/2002
• Est. Priority Date: 04/05/2001
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Medvinsky, Alexander
• Granted Patent: US 7,421,083 B2
• Time in Patent Office: Days
• US Class Current: 380/279
• CPC Class Codes: H04L 9/0822 using key encryption key
• CPC Class Codes: H04L 9/083 involving central third party, e.g. key distribution center [KDC] or trusted third party [TTP]
• CPC Class Codes: H04L 9/0891 Revocation or update of secret information, e.g. encryption key update or rekeying
• CPC Class Codes: H04L 9/3213 using tickets or tokens, e.g. Kerberos network architectures or network communication protocols for entities authentication using tickets in a packet data network H04L63/0807

Abstract

Application servers are programmed such that when an application server changes a compromised service key, the compromised key is saved by the application server until all tickets that may have been issued under the compromised key expire. Whenever the application server receives a ticket from a client issued under the compromised key, it generates an authenticator for an error message using the session key extracted from the ticket and sends the error message with this authenticator to the client. Clients are programmed to be able to receive error messages from application servers that have changed their service keys. Because the error messages include an authenticator generated by the application server using the session key extracted from the compromised ticket, the client is able to rely on the error message. The client is able to automatically request a new ticket from a key distribution center in response to a successful authentication of the error message.

Claims

1. A method for maintaining security in a communication system that provides a service to a client, the method comprising:

receiving an error message with an authenticator in response to an access request.

3. The method of claim 1 wherein the acts of receiving, decrypting and generating an authenticator are performed by a Kerberos application server.

4. The method of claim 1 further comprising retaining the compromised service key until all tickets encrypted with the compromised service key have expired.

5. The method of claim 1 further comprising

the client receiving the error message with the authenticator from an application server;

authenticating the error message; and

requesting a new ticket from a key distribution center, the new ticket for accessing the application server.

6. The method of claim 5 wherein the ticket encrypted with a service key is a Ticket Granting Ticket (TGT) and the application server is a Key Distribution Center (KDC).

7. The method of claim 5 further comprising

encrypting the new ticket with a new application server service key.

8. The method of claim 7 further comprising

requesting access to the application server using the new ticket encrypted with the new application server service key;

and

the application server authenticating the access request using the new application server service key.

2. A method for automatically recovering from a service key change in a communication system, the method comprising:

receiving a ticket from a client, the ticket being encrypted with a service key;

determining that the service key has been compromised;

decrypting the ticket using the compromised service key;

generating an error message; and

generating an authenticator for the error message, the authenticator being keyed with a session key obtained from the ticket.

9. A method for seamlessly updating a compromised service key, the method comprising:

providing a session key from the a client to an application server, the session key being encrypted by the compromised service key;

using the compromised service key to derive the session key; and

sending an error message from the application server to the client, the error message being accompanied by an authenticator keyed with the session key.

10. The method of claim 9 further comprising

authenticating the error message at the client.

11. The method of claim 9 further comprising

automatically requesting a new session key after the error message is received by the client.

12. The method of claim 11 further comprising

providing the new session key from the a client to the application server.

13. The method of claim 12 further comprising

encrypting the new session key with a new service key.

15. The method of claim 14 wherein the acts of receiving, authenticating, and requesting are performed by a Kerberos client.

16. The method of claim 14 wherein the new ticket is requested from a key distribution center.

14. A method for allowing a client to recover from a change in an application server service key, the method comprising:

receiving an authenticated error message from an application server;

authenticating the error message; and

in response to a successful authentication of the error message, requesting a new ticket for accessing the application server.

17. A processor readable storage medium, having encoded thereon processor readable program code, such that said processor readable program code is operable to cause a processor to perform a method for allowing a client to recover from a change in an application server service key, the method comprising:

receiving an authenticated error message from an application server;

authenticating the error message; and

in response to a successful authentication of the error message, requesting a new ticket from a key distribution center for the application server.

18. A processor readable storage medium, having encoded thereon processor readable program code, such that said processor readable program code is operable to cause a processor to perform a method for allowing a client to recover from a change in an application server service key from a compromised service key to a new service key, the method comprising:

receiving a ticket from a client encrypted with a compromised service key;

decrypting the ticket using the compromised service key; and

sending to the client an authenticator along with an error message, where the authenticator is keyed with a session key from the ticket encrypted with the compromised service key.