Mobile and Wireless Security (CY-803 (A)) - Unit 5 Short Notes

UNIT 5: Mobile and Wireless Security – Short Notes

I. Wireless Network Technologies and Standards

A. Wireless Local Area Networks (WLAN)

• Definition: A local area network that uses wireless communication (Wi-Fi) to connect devices within a limited area (home, office, campus).

• Core Components:

  • Access Point (AP): Central hub connecting wireless clients to the wired network.

  • Wireless Client/Station (STA): Device with a wireless network interface card (NIC).

  • Distribution System (DS): The wired backbone (usually Ethernet) interconnecting APs.

• Evolution of Wi-Fi Standards (IEEE 802.11):

*Note: Max rates are per stream/aggregate; real-world speeds are lower. \boxed{\text{OFDM}} and \boxed{\text{MIMO}} are key evolutionary pillars.

B. Wireless Personal Area Networks (WPAN)

• Definition: A network for interconnecting devices centered around an individual's workspace, typically within a range of 10 meters.

• Distinguishing Features:

  • Range: Very short (1-10m) vs. WLAN (tens to hundreds of meters), WMAN/WWAN (kilometers).

  • Topology: Often point-to-point or star (piconet) vs. infrastructure-based WLAN.

  • Power Consumption: Designed for low-power, battery-operated devices.

  • Data Rate: Can be high (Bluetooth) or low (Zigbee).

• Key Technologies:

  • Bluetooth: Short-range, frequency-hopping spread spectrum (FHSS) in 2.4 GHz. Forms piconets/scatternets. Used for peripherals, audio.

  • Zigbee (IEEE 802.15.4): Low-power, low-data-rate, low-cost. Supports mesh networking. Used in IoT, home automation.

  • IrDA: Uses infrared light for line-of-sight communication. Obsolete for general use.

C. WiMAX (Worldwide Interoperability for Microwave Access)

• Purpose: IEEE 802.16 standard for Wireless Metropolitan Area Networks (WMAN), providing last-mile broadband access.

• Physical Layer Architecture:

  • Point-to-Multipoint (PMP): Base station (BS) communicates with multiple subscriber stations (SS).

  • Mesh Mode: Optional multi-hop capability.

• Modulation Techniques:

  • OFDM (Orthogonal Frequency Division Multiplexing): Used in downlink (BS→SS). Splits channel into many orthogonal sub-carriers, resistant to multipath.

  • OFDMA (Orthogonal Frequency Division Multiple Access): Extension of OFDM for multiple users. Allocates subsets of sub-carriers (resource units) to different users, enabling flexible bandwidth allocation.

• Operational Frequency Bands & Range:

  • Licensed Bands: 2.3 GHz, 2.5 GHz, 3.5 GHz, 5.8 GHz (typical).

  • Range: Up to 50 km (line-of-sight), ~5-10 km (non-LOS). Cell radius depends on frequency and power.

D. Mesh Networks

• Concept: A network topology where each node (mesh point) can relay data for other nodes, creating multi-hop communication paths.

• Significance of Multi-Hop Relay:

  • Extended Coverage: Nodes beyond direct AP range can connect via intermediate nodes.

  • Enhanced Reliability & Fault Tolerance: Multiple paths exist; if one node/link fails, traffic reroutes.

  • Scalability: Adding nodes extends network reach without new infrastructure.

  • Self-Forming & Self-Healing: Network automatically configures and adapts to node failures.

• Advantages: Robustness, coverage extension, reduced infrastructure cost.

• Challenges: Increased latency (processing at each hop), routing overhead, potential for routing loops, security complexity (each hop is a potential attack point).

II. Cellular Mobile Communication Systems

A. Generational Evolution: 2G, 3G, 4G, and Beyond

• Key Differences:3G vs. 4G (LTE):

B. General Packet Radio Service (GPRS)

• Core Features & Capabilities:

  • Packet-Switched Domain: Overlays on 2G GSM, enabling "always-on" IP connectivity.

  • Efficient Resource Use: Shares radio channels among multiple users (statistical multiplexing).

  • Higher Data Rates: ~40-100 kbps (theoretical), via multiple time slots.

  • Supports Internet Protocols: Direct TCP/IP connection, enabling mobile web, email.

• Role: Bridge between 2G circuit-switched voice and true mobile data. Foundation for EDGE and 3G.

C. Universal Mobile Telecommunication System (UMTS)

• Architecture:

  • UE (User Equipment): Mobile device.

  • UMTS Terrestrial Radio Access Network (UTRAN): Consists of NodeBs (base stations) and Radio Network Controllers (RNCs).

  • Core Network (CN): Circuit-Switched (MSC/VLR) for voice, Packet-Switched (SGSN, GGSN) for data.

• Key Features:

  • WCDMA (Wideband CDMA): Air interface using 5 MHz bandwidth, supports higher data rates and capacity than GSM.

  • Soft Handover: Mobile can be connected to multiple NodeBs simultaneously for seamless handover.

  • Support for High-Speed Packet Access (HSPA): Evolution (HSUPA/HSDPA) boosts data rates to ~14 Mbps.

D. Long-Term Evolution (LTE)

• Position: 4G technology (pre-5G), defined by 3GPP.

• Key Features & Benefits:

  • High Throughput: Peak downlink ~300 Mbps (4x4 MIMO), uplink ~75 Mbps.

  • Low Latency: ~10 ms for user-plane data.

  • OFDMA (Downlink) & SC-FDMA (Uplink): Efficient spectrum use, resistance to multipath, flexible bandwidth (1.4-20 MHz).

  • MIMO (Multiple Input Multiple Output): Uses multiple antennas at TX/RX for spatial multiplexing (higher rates) and diversity (reliability).

  • Simplified Architecture: eNodeB (base station) connects directly to the Evolved Packet Core (EPC), removing the RNC. Flatter, lower-latency network.

  • Carrier Aggregation: Combines multiple carrier frequencies for wider bandwidth.

III. Mobility Management and Transport Layer Adaptation

A. Mobile IP

• Purpose: Enables a mobile device (Mobile Node, MN) to maintain continuous connectivity while changing its point of attachment to the internet. Uses a permanent Home Address (HoA).

• Key Entities:

  • Home Agent (HA): Router in MN's home network. Tunnels packets to MN's Care-of Address (CoA).

  • Foreign Agent (FA): Router in visited network (optional in MIPv6). Provides CoA.

  • Correspondent Node (CN): Communication peer.

• Mobile IPv4 vs. Mobile IPv6 Comparison:

• Encapsulation Header Purpose: To tunnel packets from HA to MN's current location (CoA). Outer header uses HA→CoA route; inner header uses original destination (MN's HoA).

B. TCP over Wireless Networks

• Challenges:

  • High Bit Error Rate (BER): Causes packet loss, interpreted by TCP as congestion → unnecessary congestion control (window reduction).

  • Large Round-Trip Time (RTT) & Variability: Satellite links, handoffs cause RTT spikes, affecting timeout and throughput.

  • Mobility-Induced Disconnections: Handoffs cause temporary packet loss/latency.

  • Asymmetric Links: Uplink often slower than downlink.

• Adaptations & Optimizations:

  • Split Connection / Proxy TCP: Break end-to-end TCP connection at a base station/proxy. Uses reliable link-layer (e.g., RLP) over wireless hop, and standard TCP over wired. Hides wireless errors from sender.

  • Delayed Acknowledgments: Reduces ACK traffic on uplink, saving power and bandwidth.

  • TCP Variants: TCP Westwood+ estimates bandwidth from ACKs to set congestion window after loss. TCP Veno distinguishes congestion from wireless loss.

  • Explicit Link-Layer Feedback: Link layer informs TCP of wireless losses vs. congestion losses.

IV. Ad Hoc and Mobile Networks (MANETs)

A. Routing Protocols in MANETs

• Proactive (Table-Driven): Maintains up-to-date route to every node via periodic control messages.

  • Examples: DSDV (Destination-Sequenced Distance-Vector), OLSR (Optimized Link State Routing).

  • Pros: Low latency for route discovery.

  • Cons: High control overhead in dynamic networks, wasteful if routes unused.

• Reactive (On-Demand): Discovers routes only when needed via flooding (route request).

  • Examples: DSR (Dynamic Source Routing), AODV (Ad-hoc On-demand Distance Vector).

  • Pros: Low overhead in static/semi-static networks.

  • Cons: High route discovery latency, flooding overhead.

• Hybrid: Combines proactive within a local zone, reactive between zones.

  • Example: ZRP (Zone Routing Protocol). Uses IARP (proactive intra-zone) and IERP (reactive inter-zone).

  • Goal: Balance overhead and latency.

V. RFID Technology

A. Definition and Applications

• Definition: Radio Frequency Identification. A technology that uses electromagnetic fields to automatically identify and track tags attached to objects.

• Applications: Inventory management, supply chain tracking, access control, contactless payment (NFC), asset tracking, animal tagging.

B. Principle of Operation

• Components:

  • Tag (Transponder): Microchip + antenna. Passive (no battery, powered by reader's signal), Active (battery-powered, longer range).

  • Reader (Interrogator): Emits RF signal, receives tag response. Contains antenna and RF module.

  • Antenna: On both tag and reader for signal transmission/reception.

• Data Transmission Mechanisms:

  • Inductive Coupling (Near Field): Used for Low-Frequency (LF: 125-134 kHz) & High-Frequency (HF: 13.56 MHz). Magnetic field between reader and tag coils. Short range (<1m). Used in access cards, NFC.

  • Radiative Coupling (Far Field): Used for Ultra-High Frequency (UHF: 860-960 MHz) & Microwave (2.45 GHz, 5.8 GHz). Reader emits EM waves; tag antenna receives energy and backscatters signal. Longer range (up to 10m+). Used in logistics.

• Frequency Bands & Protocols:

  • LF (125-134 kHz): Slow, short range, penetrates water/metal well. Standards: ISO 11784/11785 (animal ID).

  • HF (13.56 MHz): Medium range/speed, global ISM band. Standards: ISO 14443 (contactless smart cards, NFC), ISO 15693 (vicinity cards).

  • UHF (860-960 MHz): Fast, longer range, sensitive to environment. Standards: EPCglobal Gen2 (ISO 18000-6C) for supply chain.

VI. Security Models and Applications in Wireless Context

A. Security Models

• Military Security Models (e.g., Bell-LaPadula, Biba):

  • Primary Objectives:

    1. Confidentiality: Prevent unauthorized disclosure (Bell-LaPadula: "no read up").

    2. Integrity: Prevent unauthorized modification (Biba: "no write down").

    3. Availability: Ensure timely, reliable access.

  • Role of Hierarchical Command Structures: Enforces mandatory access control (MAC). Security levels (e.g., Top Secret, Secret) and categories (e.g., NATO, Nuclear) are centrally defined. User clearance and object classification are compared via rules (e.g., simple security property). Structure enables strict policy enforcement and audit trails.

B. Threats and Attacks

• Denial of Service (DoS):

  • Types in Wireless:

    • Physical Layer: Jamming (transmitting noise on channel), interference.

    • MAC Layer: Exhaustion attacks (flooding with RTS/CTS or authentication requests), unfair channel capture.

    • Network Layer: Routing attacks (blackhole, wormhole, rushing attack in MANETs).

    • Transport/Application Layer: SYN flood, HTTP flood.

  • Impact: Disrupts connectivity, drains battery, degrades performance.

  • Mitigation Challenges: Wireless medium is open, attacks can be launched from anywhere, hard to distinguish from legitimate traffic or channel errors.

C. Secure Applications

• E-commerce:

  • Transformation: Enabled ubiquitous access to shopping/banking anytime, anywhere. Shift from physical stores to online/mobile platforms. New business models (apps, mobile wallets, location-based offers).

  • Security Facilitation: Relies on SSL/TLS for encryption, digital certificates for authentication, secure payment gateways.

• Electronic Payment Systems:

  • Mechanisms:

    • Digital Wallets (e.g., Apple Pay, Google Pay): Store encrypted payment credentials (tokenized PAN).

    • NFC (Near Field Communication): Short-range (few cm) contactless payment. Uses HF RFID (13.56 MHz) for secure, tap-to-pay.

    • Cryptocurrency Wallets: Store private keys for blockchain transactions.

  • Security Facilitation over Networks:

    • Encryption: TLS/SSL for data in transit.

    • Tokenization: Replaces card number with a one-time token.

    • Two-Factor Authentication (2FA): Adds layer beyond password.

    • Device Security: Secure element (hardware) in phone stores credentials.