Internet protocol telephony security architecture

• US 20050027985A1
• Filed: 07/15/2004
• Published: 02/03/2005
• Est. Priority Date: 04/09/1999
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: General Instrument Corporation (CommScope Holding Company, Inc.)
• Inventors: Medvinsky, Alexander, Sprunk, Eric J., Moroney, Paul, Anderson, Steven E., Fellows, Jonathan A.
• Granted Patent: US 7,568,223 B2
• Time in Patent Office: Days
• US Class Current: 713/171
• CPC Class Codes: G06F 12/1408 by using cryptography for digital transmission H04L9/00
• CPC Class Codes: G06F 21/606 by securing the transmission between two devices or processes
• CPC Class Codes: G06F 2207/7219 Countermeasures against side channel or fault attacks
• CPC Class Codes: G06F 2211/008 Public Key, Asymmetric Key, Asymmetric Encryption
• CPC Class Codes: G06F 2221/2129 Authenticate client device independently of the user
• CPC Class Codes: H04L 63/0435 wherein the sending and receiving network entities apply symmetric encryption, i.e. same key used for encryption and decryption cryptographic mechanisms or cryptographic arrangements for symmetric key encryption H04L9/06
• CPC Class Codes: H04L 63/0442 wherein the sending and receiving network entities apply asymmetric encryption, i.e. different keys for encryption and decryption cryptographic mechanisms or cryptographic arrangements for public-key encryption H04L9/30
• CPC Class Codes: H04L 63/061 for key exchange, e.g. in peer-to-peer networks cryptographic mechanisms or cryptographic arrangements for key agreement H04L9/0838
• CPC Class Codes: H04L 63/062 for key distribution, e.g. centrally by trusted party cryptographic mechanisms or cryptographic arrangements for key distribution involving a central third party H04L9/0819
• CPC Class Codes: H04L 63/0807 using tickets, e.g. Kerberos cryptographic mechanisms or cryptographic arrangements for entity authentication using tickets or tokens H04L9/3213
• CPC Class Codes: H04L 63/12 Applying verification of the received information cryptographic mechanisms or cryptographic arrangements for data integrity or data verification H04L9/32
• CPC Class Codes: H04L 65/1043 Gateway controllers, e.g. media gateway control protocol [MGCP] controllers
• CPC Class Codes: H04L 65/1101 Session protocols
• 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 9/0841 involving Diffie-Hellman or related key agreement protocols
• 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
• CPC Class Codes: H04L 9/3263 involving certificates, e.g. public key certificate [PKC] or attribute certificate [AC]; Public key infrastructure [PKI] arrangements network architectures or network communication protocols for supporting authentication of entities using certificates in a packet data network H04L63/0823

Abstract

A secure Internet Protocol (IP) telephony system, apparatus, and methods are disclosed. Communications over an IP telephony system can be secured by securing communications to and from a Cable Telephony Adapter (CTA). The system can include one or more CTAs, network servers, servers configured as signaling controllers, key distribution centers (KDC), and can include gateways that couple the IP telephony system to a Public Switched Telephone Network (PSTN). Each CTA can be configured as secure hardware and can be configured with multiple encryption keys that are used to communicate signaling or bearer channel communications. The KDC can be configured to periodically distribute symmetric encryption keys to secure communications between devices that have been provisioned to operate in the system and signaling controllers. The secure devices, such as the CTA, can communicate with other secure devices by establishing signaling and bearer channels that are encrypted with session specific symmetric keys derived from a symmetric key distributed by a signaling controller.

Claims

1. A secure IP telephony system, the system comprising:

a signaling controller within an IP telephony network and in communication with at least one Cable Telephony Adapter (CTA), and configured to generate a symmetric sub-key in response to a request from the at least one CTA, the request including a signaling controller ticket;

wherein the signaling controller ticket comprises a signaling controller session key, an identity of the at least one CTA, and an identity of the signaling controller;

the signaling controller further configured to distribute the symmetric sub-key to the at least one CTA in response to the signaling controller ticket; and

a Key Distribution Center (KDC) within the IP telephony network and coupled to the signaling controller, and configured to generate and distribute the signaling controller ticket and a signaling controller session key to the at least one CTA using public key encryption.

2. The system of claim 1, wherein the signaling controller is configured to generate and distribute the symmetric sub-key in response to a Kerberos request from the at least one CTA.

3. The system of claim 1, wherein the signaling controller distributes the sub-key encrypted with the signaling controller session key.

4. The system of claim 1, wherein the signaling controller receives from the at least one CTA the signaling controller ticket, wherein a portion of the signaling controller ticket is encrypted with a signaling controller server key.

5. The system of claim 1, wherein the request comprises a Kerberos Application Request having the signaling controller ticket and encrypted data including a name of the at least one CTA.

6. The system of claim 1, wherein the request includes a timestamp.

7. The system of claim 1, wherein the signaling controller authenticates the at least one CTA using the signaling controller ticket.

8. The system of claim 1, wherein the signaling controller communicates with the CTA in an IPsec ESP session in response to receiving a valid signaling controller ticket.

9. The system of claim 1, wherein the KDC generates and distributes the signaling controller ticket in a Kerberos exchange with the at least one CTA.

10. The system of claim 9, further comprising a Provisioning Certificate Authority (CA) in communication with the IP telephony network configured to receive a manufacturer signed CTA certificate and distribute an operator network-specific certificate to the at least one CTA.

11. The system of claim 1, wherein the signaling controller ticket comprises a Kerberos ticket.

12. The system of claim 1, wherein the signaling controller ticket further comprises an expiration time.

13. The system of claim 1, wherein the KDC distributes to the at least one CTA the signaling controller ticket and a copy of the session key outside of the signaling controller ticket encrypted with a CTA public key.

14. The system of claim 1, wherein the KDC distributes the signaling controller ticket to the at least one CTA, and also distributes to the at least one CTA a copy of the session key outside of the signaling controller ticket encrypted using a shared secret derived from a Diffie-Hellman exchange.

15. A secure IP telephony system, the system comprising:

a Cable Telephony Adapter (CTA) coupled to an IP telephony network and comprising a public/private key pair and a public key certificate signed by a certificate authority;

a Key Distribution Center (KDC) coupled to the IP telephony network and configured to generate a ticket and session key to the CTA in response to a request from the CTA and distribute the session key to the CTA using public key encryption; and

a signaling controller coupled to the IP telephony network and configured to receive the ticket in a set up request from the CTA and generate and distribute a symmetric sub-key to the CTA in response to the set up request.

16. The system of claim 15, wherein the CTA establishes a secure session with the signaling controller based on the sub-key.

17. The system of claim 15, wherein the signaling controller is further configured to generate an end to end sub-key and send it both to the CTA and to a destination device.

18. The system of claim 17 wherein the CTA and the destination device derive at least one symmetric signaling key from the end to end sub-key.

19. The system of claim 17 wherein the CTA and the destination device derive at least one symmetric bearer traffic key from the end to end sub-key.

20. The system of claim 17, wherein the destination device is associated with a remote signaling controller and wherein the signaling controller delivers the end to end sub-key to the destination device via the remote signaling controller.

21. The system of claim 18, wherein the at least one symmetric signaling key comprises:

an Hash-based Message Authentication Code (HMAC) key; and

a Data Encryption Standard (DES) key.

22. The system of claim 21, wherein the HMAC key comprises a 160-bit Secure Hash Algorithm (SHA-1) HMAC key.

23. The system of claim 21, wherein the DES key comprises a 168-bit 3 DES key.

24. The system of claim 18, wherein the at least one symmetric bearer traffic key comprises at least one 3 DES key.

25. The system of claim 24, wherein the at least one 3 DES key comprises a first 168-bit 3-key 3 DES key for encrypting a transmit direction and a second, distinct 168-bit 3-key 3 DES key for encrypting a receive direction.

26. The system of claim 15, wherein the signaling controller is further configured to distribute an end to end sub-key to a destination device.

27. The system of claim 26, wherein the CTA is configured to communicate with the destination device using symmetric encryption keys derived from the end to end sub-key.

28. The system of claim 26, wherein the CTA is configured to communicate bearer channel traffic with the destination device using RTP packets encrypted with a at least one symmetric key derived from the end to end sub-key.

29. The system of claim 26, wherein the CTA is configured to communicate encrypted signaling messages with the destination device using an IPsec ESP session with at least one symmetric key derived from the end to end sub-key.

30. The system of claim 26, wherein the destination device comprises a remote CTA coupled to the IP telephony network.

31. The system of claim 26, wherein the destination device comprises a Plain Old Telephone Service (POTS) gateway coupled to the IP telephony network.

32. The system of claim 15, wherein the KDC is configured to distribute a Kerberos ticket to the CTA in a Kerberos exchange.

33. A secure IP telephony system, the system comprising:

a cable modem coupled to a computer-based network for transferring data to and from the cable modem and the computer based network;

one or more conventional telephones;

a Cable Telephony Adapter (CTA) coupled between the cable modem and the one or more conventional telephones, and configured to execute a cryptographic process for securing the a communications protocol and transferred data; and

one or more processors configured to execute the communications protocol to facilitate transfer of data between the CTA and the computer-based network.

34. A method of securing communications in an IP telephony system, the method comprising:

receiving a session key;

establishing a secure signaling session with a signaling controller, in part, using the session key;

receiving an end to end sub-key from the signaling controller; and

establishing secure communications with a destination device using at least one symmetric key derived from the end to end sub-key.

35. The method of claim 34, wherein establishing secure communications with the destination device comprises:

establishing a secure signaling session with the destination device, in part, using symmetric signaling keys derived from the end to end sub-key; and

establishing a secure bearer channel traffic with the destination device, in part, using symmetric bearer traffic keys derived from the end to end sub-key.

36. The method of claim 34, further comprising transmitting to a Key Distribution Center (KDC) a request for a signaling controller ticket.

37. The method of claim 34, wherein receiving the session key comprises receiving the session key in a public key encrypted message from a Key Distribution Center (KDC) in response to a request.

38. The method of claim 34, wherein receiving the session key comprises:

receiving a Kerberos ticket from a Key Distribution Center (KDC), wherein the Kerberos ticket includes a copy of the session key that is encrypted with a server key.

39. The method of claim 38, wherein the server key comprises a signaling controller key that is not accessible by Cable Telephony Adapters (CTA).

40. The method of claim 34, wherein establishing the secure signaling session with the signaling controller comprises:

transmitting a signaling controller ticket encrypted with the server key to the signaling controller;

receiving a signaling sub-key encrypted with the session key from the signaling controller ticket from the signaling controller in response to the signaling controller ticket;

deriving at least one symmetric key from the signaling sub-key; and

exchanging with the signaling controller signaling messages encrypted with the at least one symmetric key.

41. The method of claim 40, wherein the signaling controller ticket comprises a Kerberos ticket received in a Kerberos exchange with a Key Distribution Center (KDC).

42. The method of claim 34, wherein establishing secure communications with the destination device comprises:

deriving at least one symmetric signaling key from the sub-key;

deriving at least one symmetric bearer channel traffic key from the sub-key;

exchanging with the destination device signaling messages encrypted with the at least one symmetric signaling key; and

exchanging with the destination device bearer channel traffic encrypted with the at least one bearer channel traffic key.

43. A method of securing communications in an IP telephony system, the method comprising:

receiving a ticket from a Cable Telephony Adapter (CTA);

transmitting to the CTA a signaling sub-key encrypted with a session key from the ticket;

establishing secure signaling with the CTA based in part on the signaling sub-key;

receiving from the CTA a request for a call set up with a destination device;

generating a call specific sub-key;

transmitting the call specific sub-key to the destination device; and

transmitting the call specific sub-key to the CTA.

44. The method of claim 43, wherein receiving the ticket from the CTA comprises receiving a Kerberos ticket, where a secret part of the ticket is encrypted with a server key known only to the KDC and a specific signaling controller.

45. The method of claim 43, wherein establishing secure signaling with the CTA comprises:

deriving a symmetric signaling key from the signaling sub-key; and

exchanging with the CTA, signaling messages encrypted with the symmetric signaling key.

46. The method of claim 43, wherein the destination device comprises a remote CTA.

47. The method of claim 43, wherein the destination device comprises a Plain Old Telephone System (POTS) gateway.