January 23-26, 2007 Ft. Lauderdale, Florida Lawful Intercept in VoIP Networks Manohar Mahavadi Vice President, Software Engineering Centillium Communications Inc. Fremont, California

January 23-26, 2007 Ft. Lauderdale, Florida Lawful Interception – Introduction Omnibus Crime Prevention and Safe Streets Act of 1968 –Title III legalizes law enforcement wiretaps in criminal investigations Foreign Intelligence Surveillance Act of 1978 (FISA) –Wiretapping in advance of a crime being perpetrated The Electronic Communications Privacy Act of 1986 (ECPA) –Sets standards for access to cell phones, and other electronic communications and transactional records (subscriber identifying information, logs, toll records) Communications Assistance for Law Enforcement Act of 1994 (CALEA) –Preserve law enforcement wiretapping capabilities by requiring telephone companies to design their systems to ensure a basic level of government access H.R.3162 (The PATRIOT Act of 2001) –Post 9/11 –Expands the scope of Title III wiretaps and FISA to include computer fraud, abuse, etc.

January 23-26, 2007 Ft. Lauderdale, Florida Lawful Interception – CALEA (U.S.) What is CALEA? –Defines the obligations of telecom carriers to assist law enforcement agencies (LEAs) in electronic surveillance pursuant to lawful authorization –Requires carriers to design and modify their systems to ensure that electronic surveillance can be performed –Communications infrastructure should be made wiretap-ready – call forwarding, caller ID, conferencing, etc. Progress –The last decade has seen a lot of evolution of regulations backed by the FBI, FCC, DOJ, DEA –Broadened to cover many new technology solutions such as push-to-talk, SMS messaging, chat sessions, etc. for a list of standards

January 23-26, 2007 Ft. Lauderdale, Florida Lawful Interception PSTN world wiretapping –Dedicated connection – point-to-point –Dedicated resources for the call duration –Voice routed using mechanical switches or line connectivity tables –Wiretapping in local loop or at the local exchange Packet world wiretapping –Shared transmission medium: Packets contain addresses not tied to a location –Routing is dynamic and can take multiple paths –Many applications traverse the same transmission path –Decentralized VOP (SBCs, gateways, proxies, routers, switches, etc.) makes it difficult for wiretapping –Requires cooperation from infrastructure device vendors

January 23-26, 2007 Ft. Lauderdale, Florida Lawful Interception – Terminology LAES: Lawfully authorized electronic surveillance LEA: Law enforcement agency –A government entity authorized to conduct LAES (FBI, police, DEA, etc.) CC: Call content (payload of multi-media packets) CCC: Call content channel CII: Call-identifying information or call data (CD) –Signaling or dialing information that identifies origin, direction, destination or termination generated or received by a subscriber CDC: Call data channel

January 23-26, 2007 Ft. Lauderdale, Florida Lawful Interception – Terminology IAP: Intercept access point –A point within a telecommunications system or VOP network where some of the communications or CII of an intercept subject’s equipment, facilities or services are accessed Intercept subject: Subscriber whose communications, CII or both have been authorized by a court to be intercepted, monitored and delivered to an LEA Associate: The called party in the conversation TSP: Telecommunications service provider

January 23-26, 2007 Ft. Lauderdale, Florida LI – Surveillance Model Lawful Authorization Service Provider Administration Law Enforcement Administration Delivery Function Access Function Collection Function TSP LEA CII CC VoP Signaling

January 23-26, 2007 Ft. Lauderdale, Florida LI – Surveillance Model Access function (AF) –One or more IAPs Delivery function (DF) –CCCs and CDCs Collection function (CF) –Collecting and analyzing intercepted communications Service provider administration function (SPAF) –Controlling the TSP access and delivery functions Law enforcement administration function (LEAF) –Controlling the LEA collection function Mediation function (MF) –Presentation of data (CC or CII) to DF (VoIP→TDM or VoIP → VoIP)

January 23-26, 2007 Ft. Lauderdale, Florida LI – Functional Architecture CII AF CC AF CC MF CII MF CC DF CII DF Terminal LEA-CF Subject’s Domain Network’s Domain LEA’s Domain VoP Signaling VoP IAP VoP VoP, TDM VoP/Network Signaling VoP

January 23-26, 2007 Ft. Lauderdale, Florida LI – Functional Architecture 7 1 CC/CII 7 1 DF App CF App Delivery Method Delivery Method OSI Stack A-PDU Delivery Function Collection Function CCC and CDC should be separate channels CCC and CDC can share same medium

January 23-26, 2007 Ft. Lauderdale, Florida LI – Intercept Access Points Physical locations on the network from where the CC or CII is delivered to delivery function –Can be in multiple locations –CII and CC IAPs can be co-located Call identifying information IAP –CII directly associated with the call Management of an existing call between intercept subject and associate(s) (establishing, managing and releasing) –CII indirectly associated with the call ServingSystem message: Register or deregister addressing info Call content IAP

January 23-26, 2007 Ft. Lauderdale, Florida - Access Router - Border Router VOIP Phone Alice VOIP Phone Bob Bob’s VOIP SP Alice’s VOIP SP VOIP Conversation Transport ISP A Transport ISP B Transport ISP C Transport ISP D R1 R2 Call Setup VoIP SPs first enable setup VoIP calls directly take place Preferred wiretaps – R1 and R2 R1/R2 should be configured to tap Single SP makes life easier LI – Intercept Access Points Courtesy: Ref[1]

January 23-26, 2007 Ft. Lauderdale, Florida LI – Intercept Access Points Media gateways Session border controllers Access routers Signaling proxies CII and CC are typically delivered over secure channels to LEA

January 23-26, 2007 Ft. Lauderdale, Florida LI on TDM_PKT_CHANNEL LI - TDM Enc/Dec DSP NP NP Packetizer UnPacketizer B IP Phone TDM_PKT _CHANNEL A Legacy Phone EC TAP TRAFFIC COMING TO PKT LI - PKT NP Packetizer TAP TRAFFIC COMING FROM PKT NP Packetizer

January 23-26, 2007 Ft. Lauderdale, Florida LI on PKT_PKT_CHNL Encoder Decoder DSP NP Packetizer UnPacketizer A IP Phone Encoder Decoder DSP NP Packetizer UnPacketizer B IP Phone Encoder DSP NP Packetizer LI-A Encoder DSP NP Packetizer LI-B

January 23-26, 2007 Ft. Lauderdale, Florida LI – TDM_PKT_CONF_CHNL LI Model with Conferencing Courtesy: [4]

January 23-26, 2007 Ft. Lauderdale, Florida LI – Surveillance Events Information events –Call-control related events Answer: Call accepted Origination: Subject initiated a VoP session Release: Session released along with resources Termination attempt: Session termination requested –Signaling events Dialed digit extraction: Digits dialed after a call is connected Direct signal reporting: Signaling from and to intercept subject Network signal: Tone or message indicating CII (busy, ringing, etc.) Subject signal: Call waiting, forwarding, etc.

January 23-26, 2007 Ft. Lauderdale, Florida LI – Surveillance Events Information events –Feature use events Change Connection Connection break Redirection –Registration events Address registration Content events –CCChange: Media characteristics established or modified –CCClose: CC delivery is disabled –CCOpen: CC delivery is enabled –CCUnavailable: Network loses access for the call under interception

January 23-26, 2007 Ft. Lauderdale, Florida LI Challenges Security vs. CALEA requirements –Security ensures privacy, packet integrity, authenticity and non-repudiation –CALEA requires intercepted packets are not secured –SRTP and secured SIP with end-to-end security poses challenge –Peer-to-peer VoIP communication with security enabled prevents interception –Secured traffic needs to be decrypted and re-encrypted for interception Security Association termination and re-initiation –Key distribution or sharing with LEA

January 23-26, 2007 Ft. Lauderdale, Florida LI Challenges Channel capacity affected if channel duplication is required Design should consider requirements for extra performance Should support all call models like Forking, Handoff, etc. Should support all codecs in use Requires additional interface support

January 23-26, 2007 Ft. Lauderdale, Florida References [1] Security Implications of Applying the Communications Assistance to Law Enforcement Act to Voice over IP, Steve Bellovin, et al, June 13, 2006 [2] Electronics Surveillance Needs for Carrier-Grade Voice Over Packet (CGVoP) Service, FBI Document for CALEA [3] Lawfully Authorized Electronic Surveillance (LAES) for voice over Packet Technologies in Wireline Telecommunications Networks ANSI T1.678.xxxx [4] 05/2000, TIA/EIA/J-STD-025 Lawfully Authorized Electronic Surveillance, revision A: updated [5] 09/200, TIA/EIA/J-STD-025 Lawfully Authorized Electronic Surveillance, updated [6] [7]