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Wireless Overview Protocols and Threat Models Dan Veeneman [email protected] www.decodesystems.com/blackhat/bh-1.ppt Focus of this talk • • • • • Overview of available commercial technologies Skipping 802.11 U.S.-centric Terrestrial networks Additional information in second briefing Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 2 Wireless Overview Protocols and Threat Models • • • • • • • • Radio Frequency Basics Mobile telephony Cellular Digital Packet Data (CDPD) Nextel Private data networks Two-way paging Bluetooth 3G Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 3 Why Wireless • • • • • • Immediate communication, mobile user Two-way, interactive Broadcast Convenience Bandwidth limitations Roaming (no fixed location) Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 4 Market Requirements • • • • • • Reliable Low-cost Easy to use Secure Pervasive Interoperable Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 5 Wireless Security Requirements • Trust Model • access control – authenticate users to access particular resources • link privacy – encryption • link integrity – message authentication • prevent denial of service – (limit bandwidth hogs) Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 6 Radio Frequency • Federal Communications Commission • FM Radio: 88 to 108 MHz • Cellular telephones: 800 and 1900 MHz • Two-way pagers: 900 MHz • Industrial, Scientific and Medical (ISM): 2.402 to 2.480 GHz Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 7 Radio Wave • • • • Frequency Wavelength Amplitude Modulation – – – – – Amplitude Frequency Phase FSK PSK Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 8 Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 9 Generic Wireless Architecture • • • • • • • Mobile terminal Airlink Radio base station Intraconnect links Network control Interconnect links External Networks – Public Switched Telephone Network – Internet Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 10 Common Airlink Problems • • • • Variable link quality Multi-path (signal reflections) Shadowing (terrain/structure blockage) Interference – Other users – EMI • Attenuation – Distance – Antenna orientation/polarization Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 11 Multipath • Multiple paths to receiver • Each path has slightly different time delay Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 12 Interference Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 13 Error Detection/Correction • Parity Codes – Parity bits + Data bits = Expected code word • Cyclic Redundancy Check – Chunk of data + Polynomial residue • Block Codes – Chunk of data + Redundant Data • Convolutional Codes – Data stream fed through LFSR – Code rate, constraint length • Concatenated Codes Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 14 Terrestrial Networks • Voice primary – Cellular and PCS – Nextel • Data primary – private packet – paging Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 15 Cellular • • • • Analog Digital - TDMA Digital - CDMA Digital - GSM Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 16 System Comparison Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 17 Cellular Frequency Reuse • Seven frequency sets • Geographic distance between sets allows the same frequencies to be reused Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 18 Cellular-based • Mobile Telephone Switching Office (MTSO) – Controls multiple base stations – Interfaces to PSTN • Mobile is handed off from one base station to another Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 19 Advanced Mobile Phone System • • • • • • • “1G” Analog voice 50 MHz, 832 channels Mobile transmit: 824 MHz to 849 MHz Base transmit: 869 to 894 MHz 21 control channels Designed in 1970’s Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 20 Cellular Telephone startup • Mobile telephone scans for strongest control channel • Listens to overhead messages on forward link • Sends registration message – Electronic Serial Number (ESN) – Mobile Identification Number (MIN) • Waits for paging message Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 21 AMPS weaknesses • Interception is easy (but now illegal) • Spoofing (“cloned” phones) • Call hijacking • Tracking Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 22 Locating Mobiles • • • • GPS Time Difference of Arrival Angle of Arrival Multipath Fingerprinting Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 23 TDOA Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 24 AOA Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 25 Cellular Digital Packet Data • Packet data sent on idle voice channels • Voice takes priority • AT&T – “OmniSky” service • • • • Verizon IP-based interfaces 150,000 customers Many police car installs Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 26 CDPD Coverage Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 27 CDPD Elements • M-ES: Mobile End System – CDPD modem • MDBS: Mobile Data Base Station – RF interface • MD-IS: Mobile Data Intermediate System – Mobile Home Function (MHF) – Mobile Serving Function (MSF) • IS: Intermediate System – Router, IP/CNIP • F-ES: Fixed End Station Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 28 CDPD Roaming • Packets to M-ES go to MHF MD-IS first • Forwarded to MSF MD-IS • Packets from M-ES can route directly to F-ES Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 29 CDPD Airlink • GMSK modulation • 19.2 kbps raw data rate • FEC – Reed-Solomon 63, 47 block code – 47 info symbols (six-bit symbols, 282 bits), 16 parity symbols, 63 total symbols – Correct up to 8 six-bit symbols Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 30 CDPD MAC • Continuous forward link from MDBS • Mobiles listen to forward link busy/idle • Possible reverse channel collisions – Mobile checks forward link for decode success • Header, User Data, Trailer (Frame Check) • Flag, address, control fields in header • Selective ARQ Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 31 CDPD Link Establishment • M-ES known to serving MD-IS Terminal Equipment Identifier (TEI), 6 to 27 bits • M-ES sends TEI Request with 48-bit Equipment ID • MD-IS issues TEI Assign with assigned TEI • TEI lifetime of 4 hours, can be exhausted Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 32 CDPD Registration • End System Hello (ESH) message – Network Equipment Identifier (usually 32-bit IP address) – Registration Counter (to filter duplicates) – Credentials • Authentication Random Number (ARN, 64 bits) • Authentication Sequence Number (ASN, 16 bits) – Shared history (incremented by 1 after each TEI assignment) • • • • ESH sent from M-ES to MDBS encrypted ASN and ARN are both 0 at initial configuration ARN occasionally changed Network maintains two most-recent Credentials – (in case of loss of update synchronization) Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 33 CDPD Registration • MD-IS sends Redirect Request (RDR) to MHF • Requests MHF send all future packets to it • MHF checks M-ES Credentials • MHF returns Redirect Confirmation to MSF • MSF returns Hello Confirmation (ISC) to M-ES Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 34 CDPD Attacks • IP-accessible Intermediate Systems (routers) – Attacks from outside, other providers – BGP4, OSPF, buffer overflow, etc • • • • Only the airlink is encrypted Use unauthenticated RDR messages to grab traffic Brute force Credentials via repeated RDR Jam reverse link transmissions – Disrupt M-ES reception – Busy-out the reverse link (attempt saturation) – Place an analog call via CDPD cellsite • CDPD “ZAP” command to silence bad modems Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 35 Cellemetry • Use spare capacity in the cellular control channel • A few bytes • Telemetry – Vending machines – Maintenance data Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 36 Digital AMPS • • • • • • • Answer to capacity issues AT&T Wireless IS-136 800 MHz cellular and 1900 MHz PCS Time Division Multiple Access Six timeslots One call gets two timeslots Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 37 Time Division Multiple Access • Mobiles take turns transmitting • Base transmits continuously Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 38 Code Division Multiple Access • • • • • Competitor to D-AMPS IS-95 Sprint PCS, Verizon Pilot + 63 other “channels” Walsh Codes – Requires that all users in a cell be timesynchronized to maintain orthogonality • Near/Far problem, power control Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 39 Frequency Hopping • Transmissions “hop” • Pseudo-random sequence • Transmitter and receiver must synchronize • 2.4 GHz ISM – at least 75 frequencies – duration < 400 ms Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 40 Direct Sequence • Each data bit replaced with sequence of “chips” • Bandwidth increases • Power density decreases • Signals appear as noise • LPI/LPD, anti-jam • GPS, IS-95 • Chip pattern comes from Pseudo-random Noise (PN) code • Transmitter and receiver must synchronize Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 41 Correlation Example DATA: 1 0 1 1 0 1 1 0 0 1 0 0 PN: 1010 0110 0100 1111 0001 0100 1001 0100 0101 0001 0100 1011 SPREAD: 1010 1001 0100 1111 1110 0100 1001 1011 1010 0001 1011 0100 (four chips per bit) First data bit 1 becomes 4 chips, 1010 Next data bit 0 comes 4 chips, 1001 (inverted 0110) Correlation with PN Code synchronized SPREAD: 1010 1001 0100 1111 1110 0100 1001 1011 1010 0001 1011 0100 PN: 1010 0110 0100 1111 0001 0100 1001 0100 0101 0001 0100 1011 XOR: 0000 1111 0000 0000 1111 0000 0000 1111 1111 0000 1111 1111 Correlation with PN Code not synchronized (one chip off) SPREAD: 1010 1001 0100 1111 1110 0100 1001 1011 1010 0001 1011 0100 PN: 0100 1100 1001 1110 0010 1001 0010 1000 1010 0010 1001 0110 XOR: 1110 0101 1101 0001 1100 1101 1011 0011 0000 0011 0010 0010 Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 42 Problems with CDMA • Cell sites “breathe” – Combined noise of all reverse links can exceed cell site limit • Airlink different but network suffers same weaknesses as D-AMPS • Must license from Qualcomm Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 43 Global System for Mobiles • European design from the 1980s • VoiceStream, Cingular, AT&T transitioning • Short Message Service • 200 kHz channels • Eight timeslots • 270 kbps aggregate data rate • Separates equipment identity from user identity • Subscriber Information Module Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 44 International Mobile station Equipment Identity • Type Approval Code (TAC) is issued by a central authority • Final Assembly Code (FAC) identifies the place of manufacture • Serial Number (SNR) assigned by the manufacturer • Spare (SP) is reserved, usually zero. Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 45 International Mobile Subscriber Identity • Mobile Country Code (MCC) identifies the country in which the customer is subscribed. – (United States is 310) • Mobile Network Code (MNC) identifies the GSM network to which the user is subscribed, also known as the home network. – (VoiceStream is 26) • Mobile Subscriber Identification Number (MSIN) identifies the user within the network. Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 46 GSM Speech • 20 millisecond sample of speech • Digitized from codec (13 kbps) • Channel coding (22.8 kbps) • Interleaving • Encrypting • Burst formatting (33.8 kbps) • Modulation (270 kbps) Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 47 GSM has weak crypto • Security by Obscurity – Algorithms never officially released – All of them leaked or reverseengineered • A3/A8 in SIM • A5 in hardware • A5 (privacy algorithm) deliberately weakened – A8 feeds it weakened keys – Weaker algorithm (A5/2) for export Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 48 Short Message Service • 20 billion SMS messages per month from 553 million GSM subscribers • Carried in GSM logical data channel • Increasing applications – Youth market (Instant Messenger) – eBay outbidding – Remote monitoring • TDMA and CDMA have similar – “Tacked on” Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 49 Some SMS Issues • Early pre-pay phones had free SMS due to lack of billing system integration • SMS Identity spoofing – Faked “caller-ID” data • SMS viruses • Crash certain phones – Badly-formatted binary messages Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 50 Integrated Dispatch Enhanced Network (iDEN) • Grew out of Specialized Mobile Radio (SMR), dispatch/group environment • Equipment from Motorola • Service from Nextel • TDMA, 6 timeslots, 15 ms each • Continuous forward control channel • VSELP voice • Test equipment can monitor Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 51 Mobitex • • • • • Cingular Interactive (US) Rogers (Canada) “Palm.Net” service Ericsson standard 700,000 customers Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 52 Mobitex coverage Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 53 Mobitex • • • • • • • 2,500 U.S. base stations 30 mile radius 10 - 30 channels per site 12.5 kHz 8 kbps signaling rate 895 - 910 MHz 2 watts Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 54 Mobitex monitoring • Specification publicly available • Source code to monitor released on Usenet – Receiver with 800 MHz coverage – PC with simple interface board • Network interfaces via Internet, frame relay, X.25 Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 55 Advanced Radio Data Information System (ARDIS) • • • • • • IBM field personnel, Motorola network Motient (US), Bell Mobility (Canada) 40 million messages/month 1,500 base stations 40 watt transmitter, 10 - 15 mile range X.25 or TCP/IP to ARDIS switch Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 56 ARDIS Network • Radio Packet Modem (RPM) • Base stations talk to Radio Network Controller (RNC) via leased lines with dialup restoral • Switch is “ARDIS Service Engine” Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 57 ARDIS Airlink • • • • • DataTac 4000 (US) MDC 4800 or RD-LAP 19.2 2048 maximum message 240 or 512 byte max packet payload Logical Link Identifier (unique device ID), either 4 or 8 bytes • CRC and FEC Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 58 ARDIS Protocols • Standard Context Routing (SCR) – Basic Inbound (from server to mobile) – Basic Acknowledgement (mobile ACK) – Basic Outbound (from mobile to server) • Peer-to-peer – “Message Generator” (MG) protocol – Poorly validated field values • Sender (spoof) • Recipient (spam) • Message length (crash client application) Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 59 ARDIS Message Filtering • Radio Packet Modem uses Hayes AT commandstyle interface • “The modem’s two-character S50 register contains the current user header. When a wireless modem receives an outbound message from the ARDIS network, the modem examines the user header in the message header. If the user header in the message matches the user header in an S50 register, the message can be received. If it does not match, the message is discarded.” – ATS50=QA Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 60 ARDIS Security Recommendations • “Customers with sensitive data may want to provide data encryption within their applications. For example, an exclusive OR could be applied to ASCII data with a randomly generated encryption key selected for each terminal during logon. • NOTE: Only user data can be encrypted; ARDIS must be able to read SCR and other user header data to determine the proper disposition of a message.” • “A wireless device application should allow a command from the host to dump all RAM contents and disable the application. This command could be used if a wireless device were lost or stolen. This feature could be activated automatically when a logon is attempted, or by a host user.” Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 61 MicroCellular Data Network (Ricochet) • • • • • Mesh topology FHSS, every 10 - 25 ms Synchronous heartbeat, 30 sec Ricochet modems: 900 MHz Poletop radios: 2.3, 2.4 GHz – Density 5 - 12 per square mile • Wireless Access Point (WAP) – Covers 10 - 12 square miles Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 62 Ricochet Network • • Name Server: The Ricochet Name Server maintains access control and routing information for every radio and service within the Ricochet network. Every time a Ricochet device (subscriber device, microcell radio, or gateway) is powered on, it registers with the Name Server to verify that it has network authorization. Whenever a Ricochet device requests a connection, the Name Server validates the request. If authorized, the originator is provided with a network routing path to the requested destination. MCDN Path – – • List of addresses (IP, phone number, microcell number) of waypoints part of header, used to route the packet Packet delivery services – – Lightweight: in-order, windowed, no end-to-end retries Heavyweight: in-order, windowed, end-to-end retries Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 63 Metricom and Ricochet • Metricom • 51,000 customers in 21 cities • Bankruptcy • Ricochet Networks (part of Aerie Networks) • Gen II: 176 kbps, up to 400 kbps bursts Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 64 FLEX (One-way paging) • Four level FSK • 1600, 3200, 6400 bps • Four-minute FLEX protocol cycle • Short capcodes: 7 digits • Long capcodes: 9 digits • FLEXsuite: 128-bit RC4, symmetric keys Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 65 ReFLEX (Two-way paging) • • • • Narrowband PCS Nationwide frequencies Forward: 896-902 MHz Reverse: 929 - 931, 940 941 MHz Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 66 ReFLEX inbound messaging • Send request on shared ALOHA channel • Receive timeslot assignment • Send data in assigned timeslot on data channel Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 67 ReFLEX forward link • • • • ReFLEX frame is 1.875 s 128 frames = cycle (4 minutes) 21 data, 11 error correction (21,32) BCH “collapse”, sleep for 2n frames Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 68 Bluetooth • Peer-to-peer, proximity-based “personal area network” • Low power, short range • Multiple devices in a “piconet” – one device is master • Up to 10 piconets may link to form “scatter nets” • Each device has a unique 48bit address • Initialization process uses a PIN Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 69 Bluetooth Airlink • • • • • • • • • • 2.45 GHz 1,600 hops per second Master and up to 7 active Slaves Hop sequence based on master’s address GMSK, BPSK FEC Master: up to 721 kbps, even timeslots Slave: 57.6 kbps, odd timeslots 79 frequencies 3.2 kHz clock, 28 bits Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 70 Bluetooth device modes • Four modes: – – – – active (continuous) sniff (check at intervals) hold (check again later) park (listen for beacon only) Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 71 Bluetooth Protocol Stack • Application Group • Middleware Protocol Group • Transport Protocol Group Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 72 Transport Protocol Group • Radio • Baseband • L2CAP (Logical Link Control and Adaptation Protocol) – Protocol multiplexing – Fragmentation/reassembly • Audio • Control • Link Manager Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 73 Bluetooth Identifiers • • • • Device Address, 48 bits Private Authentication Key, 128 bits Private Encryption Key, 8 to 128 bits RAND, 128 bits Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 74 Bluetooth Security Modes • Security Mode 1 – non-secure • Security Mode 2 – service-level – after channel establishment • Security Mode 3 – link-level – prior to channel establishment Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 75 Bluetooth Security Levels • Device – Trusted – Untrusted • Service – Authorization and Authentication – Authentication Only – Open to all devices Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 76 Bluetooth Unit Key • Unit Key – E21( Device Address, Random Number) – Usually fixed for the lifetime of the device Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 77 Bluetooth Initial Key Generation • Verifier sends Claimant IN_RAND • Verifier computes Kinit from E22( IN_RAND, PIN) • Kinit is temporary link key • PIN can be – Fixed in simple device – Keyed in by user (typically 4 digits) – Generated by user device Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 78 Bluetooth Authentication 1. Device A generates AU_RAND and sends it to Device B 2. Device B sends Device AddressB to Device A 3. Device A and Device B both compute SRES and ACO from SAFER+ based MAC function E1(Kinit, AU_RAND, Device Address ) 4. Device B sends SRESB to Device A 5. If SRESA equals SRESB, then devices are authenticated Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 79 Bluetooth Link Key • Two types of link keys • Unit key of one of the devices – Unit A computes K = KA XOR Kinit and sends K to Unit B – Unit B computes KA = K XOR Kinit – KA is used as link key • Key derived from both unit keys – Unit A generates LK_RANDA, sends it to Unit B and computes LK_KA = E21(LK_RANDA, Device AddressA ) – Unit B generates LK_RANDB, sends it to Unit A and computes LK_KB = E21(LK_RANDB, Device AddressB) – Both units compute each other’s key and the link key KAB = LK_KA XOR LK_KB Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 80 Bluetooth Encryption Key • KC = E3( EN_RANDA, Klink, COF ) • Ciphering Offset Figure (COF) – Authenticated Ciphering Offset (ACO) or – For broadcast, Device Address concatenated with itself Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 81 Bluetooth Encryption • Kcipher = E0( Device AddressA, clockA, KC ) • Data is exclusiveOR’ed with Kcipher before transmission and after reception Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 82 Bluetooth Security Issues • Privacy – Devices can be closely tracked • Only devices are authenticated, not users • Key variables exchanged in the clear • Link key a shared secret among too many – A, B use A’s unit key as the link key – B can later use A’s unit key and a faked address to eavesdrop on traffic Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 83 3GPP • • • • 3rd Generation Partnership Project Crypto developed in the open Air interface will use KASUMI encryption Evolve GSM – Multimedia Messaging Service (MMS) – General Packet Radio Service (GPRS) • GSM overlay (Phase 1: 4x14 kbps, Phase 2: 8x14kbps) • Cingular,AT&T: TDMA to GSM to GPRS – Enhanced Data rates for GSM Evolution (EDGE) – Universal Mobile Telephone Service (UMTS) – High Speed Circuit Switched Data (HSCSD) Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 84 Questions? Black Hat Briefings July 31, 2002 Wireless Overview Protocols and Threat Models Page 85