1. MWIF Confidential MWIF-Arch Security Task Force Task 5: Security for Signaling July 11, 2001 Baba, Shinichi (sbaba@tari.toshiba.com) Ready for MWIF Kansas City TC meeting

2. MWIF Confidential Overview Task 5: “Examine Signaling Security” for the All IP wireless network General idea of security for signaling Consideration of security on SIP –SIP is the tacit signaling protocol currently assumed in the MWIF NRA

3. MWIF Confidential General discussion Signaling Security: to avoid the malicious attack through signaling (message) Basics: encryption and authentication –Ref: End-to-End and Overall security (mwif2001.104) Variety of layer for implementation: –Network layer (e.g., IPSEC) –Transport layer (e.g., TSL/SSL) –Application layer (e.g., WWW-authentication)

4. MWIF Confidential Legacy vs All IP In the legacy system, i.e., SS7 –Dedicated link base –Poor user interface for signaling –Authentication of inter-service provider signaling In the IP based system, i.e., All IP –No separation between signaling channel and bearer channel –Easy to send a spoofing signaling message and to monitor the signaling message

5. MWIF Confidential Node-to-node model Signaling message exchange with security based on SA Network-1 Network-2 BR BR : Border Router SA : Security Association

6. MWIF Confidential Network-to-network model Signaling message exchange with security based on SA Signaling message exchange without security Protected Network-1 Protected Network-2 FW SG : Security Gateway FW : Firewall SG FW

7. MWIF Confidential Examination of models Node-to-NodeNetwork-to-Network Pros Robust (No single point of failure) Flexible (less architecture restriction) Small number of SA to manage Easy to implement and operate Cons Mean for the dynamic SA establishment, maybe PKI Single point of failure

8. MWIF Confidential Security of SIP Basic investigation in draft “2543bis” –Confidentiality –Authentication –etc... Issues still being worked –Integrity of request and response Predictive nonce for digest –Registration and SA –etc...

9. MWIF Confidential Confidentiality in SIP End-to-end –Cannot encrypt whole message –Header evaluated and modified by the SIP server (i.e., proxy, redirect and register) Hop-by-hop –Use transport or lower layer method

10. MWIF Confidential Authentication in SIP Borrow from HTTP, “Basic” and “Digest” –Though, Basic is NOT recommended to use –WWW-Authenticate/Authorization for called user –Proxy-Authenticate/Proxy-Authorization for server –A kind of weakness to replay and MITM (man-in- the-middle) attacks Predictive nonce –Hop-by-hop authentication may be supported by under layer mechanism.

11. MWIF Confidential Privacy and so on Privacy of the called user –Called user information (location or availability) may be carried to the caller. –Required careful network design Denial of Service –Spoofing ‘Via’ header –6xx responses from a rogue proxy

12. MWIF Confidential Summary General idea of Signaling Security –Difference: Legacy vs All IP –Node-to-node and Network-to-network Security for SIP –Confidentiality, Authentication, Privacy and DoS protection –Network design is important, since SIP doesn’t provide a whole security solution only by itself. Modification protocol hop-by-hop security