System for seamlessly updating service keys with automatic recovery
View Patent ↗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.
1. 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 indicative of the detection of the compromised service key;
generating an authenticator to be sent to the client for authenticating the error message, the authenticator being keyed with a session key derived from the compromised service key; and
sending the authenticator to the client.
2. The method of claim 1 wherein the acts of receiving, decrypting and generating an authenticator are performed by a Kerberos application server.
3. The method of claim 1 further comprising retaining the compromised service key until all tickets encrypted with the compromised service key have expired.
4. 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 utilizing 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.
5. The method of claim 4 further comprising authenticating the error message at the client.
6. The method of claim 4 further comprising automatically requesting a new session key after the error message is received by the client.
7. The method of claim 6 further comprising providing the new session key from the client to the application server.
8. The method of claim 7 further comprising encrypting the new session key with a new service key.