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CY-803 (A) · Mobile and Wireless Security/Quick Revision Short Notes

Mobile and Wireless Security (CY-803 (A)) - Unit 1 Short Notes

A. WIRELESS NETWORKING TECHNOLOGIES & EVOLUTION

Wi-Fi / Wireless Local Area Network (WLAN)

  • Definition: A WLAN is a local area network that uses wireless communication (typically IEEE 802.11 standards) to connect devices within a limited area.

  • Core Components:

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

    • Station (STA): Wireless client device (laptop, phone).

    • Wireless Distribution System (WDS): Enables inter-AP communication for extended coverage.

  • Evolution of Wi-Fi Standards:

    | Standard | Year | Max Speed | Band | Key Tech | Trend Implications | |----------|------|-----------|------|----------|-------------------| | 802.11a | 1999 | 54 Mbps | 5 GHz | OFDM | Early high-speed, less interference | | 802.11b | 1999 | 11 Mbps | 2.4 GHz | DSSS | Popular, low-cost, crowded band | | 802.11g | 2003 | 54 Mbps | 2.4 GHz | OFDM | Backward compatible with b | | 802.11n | 2009 | 600 Mbps | 2.4/5 GHz | MIMO, 40 MHz | Multi-stream, high throughput | | 802.11ac | 2013 | 3.5 Gbps | 5 GHz | MU-MIMO, 160 MHz | High-density, video streaming | | 802.11ax (Wi-Fi 6) | 2019 | 9.6 Gbps | 2.4/5/6 GHz | OFDMA, MU-MIMO | IoT, dense deployments, efficiency | | 802.11be (Wi-Fi 7) | 2024 | 46 Gbps | 2.4/5/6 GHz | 320 MHz, 16 MU-MIMO | Extreme throughput, low latency |

  • Fundamental Operations:

    • Infrastructure Mode: STAs communicate via AP.

    • Ad-hoc Mode (IBSS): Direct STA-to-STA without AP.

    • SSID: Network name identifier.

    • Channels: Frequency bands (e.g., 2.4 GHz: 11 channels in US; 5 GHz: more, less overlap).

  • Security Paradigms Evolution:

    • WEP (1999): RC4 stream cipher, weak IVs, easily cracked.

    • WPA (2003): TKIP (temporary fix), per-packet key mixing.

    • WPA2 (2004): AES-CCMP mandatory, robust security (but vulnerable to KRACK).

    • WPA3 (2018): SAE (Simultaneous Authentication of Equals) for forward secrecy, 192-bit security suite.

[!TIP] Common pitfall: Confusing WPA (TKIP) with WPA2 (AES). WPA3 replaces pre-shared key (PSK) with SAE to resist offline dictionary attacks.

Wireless Personal Area Network (WPAN)

  • Definition: Short-range (typically ≤10 m), low-power wireless network for personal device connectivity.

  • Distinguishing Characteristics vs. Other Wireless Networks:

    | Feature | WPAN | WLAN | WMAN | WWAN | |---------|------|------|------|------| | Range | ~10 m | ~100 m | km | km to global | | Data Rate | Low to medium (≤100 Mbps) | High (≥100 Mbps) | Medium | Medium | | Power Consumption | Very low (mW) | Medium (W) | Medium | High (W) | | Typical Topology | Star, piconet | Infrastructure/ad-hoc | Point-to-multipoint | Cellular (hierarchical) |

  • Key Technologies:

    • Bluetooth (IEEE 802.15.1):

      • Piconet: 1 master + up to 7 active slaves (frequency-hopping spread spectrum, 2.4 GHz).

      • Scatternet: Interconnected piconets (a device can be master in one, slave in another).

    • Zigbee (IEEE 802.15.4): Low-power, low-data-rate, supports mesh networking; used in IoT, home automation.

    • IrDA (Infrared Data Association): Line-of-sight, short-range (≤1 m), obsolete for general use.

WiMAX (Worldwide Interoperability for Microwave Access)

  • Definition & Scope: IEEE 802.16 standard for metropolitan area wireless broadband (fixed and mobile).

  • Physical Layer:

    • Operating Frequency Bands: Licensed (2–11 GHz) and unlicensed (5 GHz).

    • Modulation Techniques:

      • OFDM (Orthogonal Frequency Division Multiplexing): Downlink, robust against multipath.

      • OFDMA (Orthogonal Frequency Division Multiple Access): Uplink, assigns subcarriers to multiple users dynamically.

  • Network Architecture & Service Types:

    • Components: Subscriber Station (SS), Base Station (BS), Access Service Network (ASN), Connectivity Service Network (CSN).

    • Services: Residential broadband, business connections, backhaul for other networks.

Cellular & Mobile Broadband Evolution

  • GPRS (General Packet Radio Service):

    • Key Features: Introduces packet-switched domain in 2G networks; "always-on" connectivity; higher data rates (theoretical up to 114 kbps).

    • Architecture: Adds GGSN (Gateway GSN, connects to external networks) and SGSN (Serving GSN, tracks mobile location).

    • Role: Enabled mobile internet (email, web) on GSM networks.

  • UMTS (Universal Mobile Telecommunication System):

    • 3G Technology Overview: Uses W-CDMA (Wideband CDMA) for higher capacity and data rates.

    • Core Network Evolution:

      • UTRAN (UMTS Terrestrial RAN): Node B (base station) and RNC (Radio Network Controller).

      • CN (Core Network): MSC (circuit-switched voice), SGSN/GGSN (packet-switched data).

    • Key Features: Peak data rates up to 2 Mbps (static), support for mobile multimedia (video calls).

  • 3G vs. 4G (LTE) Comparative Analysis:

    | Aspect | 3G (UMTS) | 4G (LTE) | |--------|-----------|----------| | Technology | CDMA (W-CDMA) | OFDMA (downlink), SC-FDMA (uplink) | | Core Network | Hybrid: Circuit-switched (MSC) + Packet-switched (SGSN/GGSN) | All-IP (EPC: MME, S-GW, P-GW) | | Peak Data Rates | ~2 Mbps | ~1 Gbps (downlink), 500 Mbps (uplink) | | Latency | ~100 ms | ~10 ms | | Architecture | Hierarchical (Node B → RNC → CN) | Flat (eNodeB directly to EPC) | | Primary Services | Voice, SMS, mobile data | Mobile broadband, VoIP, HD video streaming |

  • LTE (Long-Term Evolution):

    • Key Features:

      • All-IP Network: No circuit-switched domain.

      • Flat Architecture: eNodeB (evolved Node B) connects directly to EPC (Evolved Packet Core).

      • MIMO (Multiple Input Multiple Output): 2x2 or 4x4 antenna arrays for spatial multiplexing.

      • Carrier Aggregation: Combine multiple carriers (up to 5) for wider bandwidth.

    • Benefits: High throughput (100 Mbps downlink typical), low latency, improved spectral efficiency.

    • Relationship to 4G/5G: LTE is the dominant 4G standard; 5G (NR) builds on LTE with new radio and network slicing.

Radio Frequency Identification (RFID)

  • Definition & Components:

    • Tag: Contains microchip and antenna (passive, active, semi-passive).

    • Reader: Transmits RF signal and receives tag response.

    • Middleware: Filters and processes raw tag data.

    • Database: Stores tag-associated information.

  • Principle of Operation:

    • Inductive/Capacitive Coupling (LF/HF): Magnetic field between reader and tag coils (near-field).

    • Backscatter Communication (UHF): Reader emits RF; tag reflects (backscatters) modulated signal (far-field).

  • Data Transmission:

    • Tag Powering:

      • Passive: Powered by reader's RF energy (no battery, short range).

      • Active: Battery-powered, long range, can initiate transmission.

      • Semi-passive: Battery for chip, but communication via backscatter.

    • Protocols: EPCglobal (supply chain), ISO 18000 (international standard).

    • Communication: Reader-to-tag (command via RF), tag-to-reader (backscatter or active transmission).

  • Frequency Bands & Applications:

    • LF (125–134 kHz): Short range (≤10 cm), animal tagging, access control.

    • HF (13.56 MHz): Medium range (≤1 m), NFC, library books, smart cards.

    • UHF (860–960 MHz): Long range (up to 10 m), inventory, logistics, retail.

[!TIP] RFID passive tags have no internal power source; they harvest energy from the reader's signal. Active tags have batteries and can transmit autonomously.

B. MOBILE NETWORKING & PROTOCOLS

Mobile IP (Internet Protocol)

  • Core Problem: Enable seamless mobility while maintaining a permanent IP address (home address) across different networks.

  • Mobile IPv4 vs. Mobile IPv6 Key Differences:

    | Feature | Mobile IPv4 | Mobile IPv6 | |---------|-------------|-------------| | Home Agent (HA) | Required | Required | | Foreign Agent (FA) | Required (provides CoA, routing) | Not required (MN uses co-located CoA) | | Care-of Address (CoA) | FA's address or co-located | Only co-located (derived from prefix) | | Tunneling Mechanism | IP-in-IP encapsulation | Routing Header (Type 2) | | Security | Optional (often insecure) | Mandatory IPsec (for binding updates) | | Route Optimization | Optional (via FA) | Standard (via Binding Updates) | | Address Space | 32-bit (limited) | 128-bit (vast) |

  • Core Entities:

    • Mobile Node (MN): Device that changes point of attachment.

    • Home Agent (HA): Router in MN's home network; tunnels packets to MN's CoA.

    • Foreign Agent (FA): Router in visited network (MIPv4 only); provides CoA and forwarding.

    • Care-of Address (CoA): Temporary IP address used while visiting a foreign network.

  • Operation:

    1. Agent Discovery: MN listens for Agent Advertisements (HA/FA) or solicits them.

    2. Registration: MN registers its CoA with HA (and FA in MIPv4) via REGISTRATION REQUEST.

    3. Tunneling/Triangle Routing: Packets from CN to MN's home address are intercepted by HA and tunneled to CoA.

    4. Route Optimization (MIPv6): MN sends Binding Update to CN, allowing direct routing to CoA, avoiding triangle routing.

Routing in Wireless Ad Hoc & Mesh Networks

  • Ad Hoc Networks: Infrastructure-less, multi-hop, self-organizing; nodes act as routers.

  • Routing Protocol Categories:

    • Proactive (Table-Driven): e.g., DSDV (Destination-Sequenced Distance Vector), OLSR (Optimized Link State Routing).

      • Mechanism: Maintains up-to-date routes via periodic control messages (e.g., link-state advertisements).

      • Pros: Low latency for data transmission (routes always available).

      • Cons: High overhead in large/dynamic networks (scales poorly).

    • Reactive (On-Demand): e.g., AODV (Ad-hoc On-Demand Distance Vector), DSR (Dynamic Source Routing).

      • Mechanism: Discovers routes only when needed via route request (RREQ)/reply (RREP) floods.

      • Pros: Low overhead in low-traffic networks.

      • Cons: Route discovery delay; susceptible to route request storms.

    • Hybrid: e.g., ZRP (Zone Routing Protocol).

      • Mechanism: Combines proactive within a local "zone" (e.g., 2-hop neighborhood) and reactive between zones.

      • Goal: Balance overhead and latency.

  • Mesh Networks:

    • Concept: Multi-hop relay via mesh routers (often with fixed infrastructure); devices may connect to nearest router.

    • Significance:

      • Extended Coverage: Routers relay traffic beyond single-hop range.

      • Reliability: Redundant paths allow rerouting around failures.

      • Self-Healing: Automatic route adjustment when nodes fail.

      • Scalability: Can cover large areas with many routers.

    • Distinction from Pure Ad Hoc: Mesh networks often have planned, stationary routers; ad hoc is fully dynamic with all nodes mobile.

TCP over Wireless Networks

  • Challenges:

    • High Bit Error Rate (BER): Causes packet loss unrelated to congestion.

    • Variable Latency: Handoffs, interference cause delay spikes.

    • Bandwidth Asymmetry: Downlink often higher than uplink.

    • Disconnections: Temporary loss of connectivity (e.g., moving out of range).

  • Performance Issues:

    • Spurious Timeouts: TCP interprets wireless loss as congestion, reducing congestion window unnecessarily.

    • Congestion Window Reduction: Degrades throughput due to non-congestion losses.

  • Solutions/Approaches:

    • Split TCP: Proxy at base station breaks connection; local retransmissions hide wireless losses from sender.

    • Snooping: Base station snoops ACKs and locally retransmits lost packets.

    • Selective Retransmission: Link layer provides selective repeat rather than go-back-N.

    • TCP Variants: e.g., TCP Westwood+ estimates bandwidth from ACKs to set congestion window/reset threshold.

    • Link Layer Retransmissions: Hide errors at lower layer (but can cause head-of-line blocking if not selective).

[!TIP] Wireless packet loss is often due to channel errors, not congestion. Standard TCP misinterprets this as congestion, leading to underutilization. Solutions aim to decouple wireless loss from congestion signals.

C. NETWORK LAYER & ENCAPSULATION FUNDAMENTALS

Encapsulation Headers in IPv4 & IPv6

  • Purpose of Encapsulation Headers:

    • Tunneling: Wrap original packet within new header (e.g., Mobile IP, VPNs).

    • Mobility: Mobile IP uses tunneling to deliver packets to mobile node's CoA.

    • Security: IPsec adds AH/ESP headers for authentication/encryption.

  • IPv4 Encapsulation Header Structure (20 bytes fixed, plus optional fields):

    • Version: 4

    • IHL (Internet Header Length): Header length in 32-bit words.

    • Type of Service (ToS): Precedence, delay, throughput, reliability bits.

    • Total Length: Header + data length.

    • Identification: For fragmentation/reassembly.

    • Flags: Don't Fragment, More Fragments.

    • Fragment Offset: Position of fragment in original datagram.

    • TTL (Time to Live): Decremented per hop; prevents loops.

    • Protocol: Indicates next layer protocol (e.g., 6=TCP, 17=UDP).

    • Header Checksum: Error detection for header only.

    • Source IP Address: 32-bit.

    • Destination IP Address: 32-bit.

    • Options (optional): Rarely used (e.g., security, timestamp).

  • IPv6 Encapsulation Header Structure (40 bytes fixed, followed by extension headers):

    • Version: 6

    • Traffic Class: QoS priority (like ToS).

    • Flow Label: Identifies packet flow for special handling (20 bits).

    • Payload Length: Length of extension headers + data.

    • Next Header: Type of first extension header or upper layer protocol.

    • Hop Limit: Replaces TTL.

    • Source Address: 128-bit.

    • Destination Address: 128-bit.

    • Extension Headers (optional): Hop-by-Hop, Routing, Fragment, Destination, AH, ESP.

  • Key Comparison:

    | Feature | IPv4 | IPv6 | |---------|------|------| | Header Size | Variable (20–60 bytes) | Fixed 40 bytes (plus extensions) | | Address Length | 32-bit | 128-bit | | Checksum | Header checksum present | No header checksum (rely on link layer & upper layers) | | Fragmentation | Done by routers and source | Only by source (router fragmentation forbidden) | | Options | In-header (variable) | Extension headers (chainable) | | Flow Identification | Not native | Flow Label field | | Security | Optional (IPsec) | Mandatory IPsec support (but not enforced) |

[!TIP] IPv6 eliminates header checksum to reduce per-hop processing; relies on lower-layer error detection. Extension headers allow flexible feature addition without fixed header size.

D. SECURITY MODELS & APPLICATIONS

Military Security Models

  • Primary Objectives: Beyond CIA triad (Confidentiality, Integrity, Availability), include:

    • Non-Repudiation: Prevent denial of actions (e.g., sending a message).

    • Authentication: Verify identity of users/systems.

    • Authorization: Ensure access based on clearance and need-to-know.

  • Hierarchical Command Structures:

    • Role in Access Control: Enforces need-to-know basis; information flows according to rank (e.g., Bell-LaPadula model: "no read up, no write down").

    • Information Flow Policy: Prevents unauthorized data leakage across security levels.

    • Incident Response: Clear chain of command for reporting and mitigating security breaches.

Denial of Service (DoS) & Distributed DoS (DDoS)

  • Definition & Goal: Attack aims to disrupt availability of a service/network by overwhelming resources (bandwidth, memory, CPU).

  • Common Attack Vectors in Wireless/Mobile:

    • Jamming: Transmit noise on physical layer to interfere with legitimate signals (e.g., 802.11 channels).

    • Authentication Exhaustion: Flood AP with authentication requests (e.g., 802.11 deauthentication/disassociation frames).

    • Resource Consumption: TCP SYN flood, HTTP flood, or malformed packets that consume connection tables.

    • Battery Drain Attacks: Force device to perform energy-intensive operations (e.g., repeated encryption, keep-alive requests).

  • Wireless-Specific Challenges:

    • Easier to Launch: Broadcast medium; no need for physical access.

    • Attribution Difficulty: Spoofed MAC/IP addresses; attacker can be mobile.

    • Impact on Network Resources: Shared medium; attack affects all nearby users.

E-Commerce & Electronic Payment Systems

  • E-Commerce:

    • Definition: Buying/selling goods/services over electronic networks (primarily internet).

    • Transformation of Business:

      • Models: B2B, B2C, C2C (e.g., eBay), C2B.

      • Reduced Transaction Costs: Automation, no physical stores.

      • Global Reach: Access to worldwide markets.

      • New Models: Subscriptions, digital goods, auctions, on-demand services.

  • Electronic Payment Systems:

    • Types:

      • Card-based: Credit/debit cards via payment gateways (e.g., Stripe, PayPal).

      • Digital Wallets: Store payment info (e.g., Apple Pay, Google Wallet) using tokenization.

      • Electronic Checks: E-check processing via ACH networks.

      • Cryptocurrencies: Decentralized digital currencies (e.g., Bitcoin) using blockchain.

    • Facilitation of Transactions:

      • Authentication: User verification (passwords, 2FA, biometrics).

      • Encryption: Protect data in transit (TLS/SSL).

      • Non-Repudiation: Digital signatures ensure parties cannot deny transactions.

    • Security Requirements: Confidentiality (data encryption), Integrity (tamper-proof), Authentication (entity verification).

  • Security Context in Mobile/Wireless:

    • M-Commerce: Mobile-specific e-commerce (apps, mobile browsers).

    • Mobile Payments: NFC-based contactless payments, QR codes.

    • Threats: Interception (eavesdropping on wireless), fraud (stolen credentials), mobile malware (trojans in apps).

[!TIP] In mobile payments, tokenization replaces card numbers with one-time tokens to reduce fraud. NFC requires close proximity (≤10 cm), mitigating remote interception.

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