Mobile Appliance Security: Concerns and Challenges

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Mobile Appliance Security Concerns and Challenges

• Mahesh Mamidipaka
• ICS 259 Seminar in Design Science

1. Securing Mobile Appliances New Challenges for
the System Designer - A. Raghunathan, S.
Ravi, S. Hattangady, J. Quisquater (DATE 03) 2.
Masking Energy Behavior of DES Encryption -
H. Saputra, N. Vijaykrishnan, N. Kandemir, et al.
(DATE 03) 3. Wireless Network Security - Tom
Karrygiannis and Jes Owens, NIST
http//csrc.nist.gov/publications/nistpubs/800-48/
NIST_SP_800-48.pdf
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Outline

• Introduction
• Security Concerns
• Design Challenges
• Security Attacks on Smart Cards
• Power analysis based attack
• Masking Energy Behavior for DES Encryption (DATE
  03)

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Introduction

• Mobile appliances widely used (PDAs, Cell Phones,
  Smart Cards, etc.)
• Involves sensitive information increased
  security concerns
• Success of emerging technologies to depend on
  ensuring adequate security
• Security cited as single largest concern among
  prospective m-commerce users

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Unique Challenges

• Knowledge and experience from wired internet
  gives us a head start (not sufficient)
• Unique challenges
• Use of public transmission medium
• Potentially unlimited points of access
• Vulnerable to theft, loss, and corruptibility
• Constraints on power, cost, and weight
• Need for techniques at every aspect of design to
  meet the challenges

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Outline

• Introduction
• Security Concerns
• Design Challenges
• Security Attacks on Smart Cards
• Masking Energy Behavior for DES Encryption

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Security Issues
Tamper-resistant Implementation
User Identification
Secure Content
Secure Network Access
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Secure Data Communication

• Employ security protocols to various layers of
  network protocol stack
• Achieve peer authentication, privacy, data
  integrity etc.
• cryptographic algorithms act as building blocks
• Examples Network layer protocols
• Cellular technologies GSM, CDPD
• Wireless LAN IEEE 802.11
• Wireless PAN Bluetooth
• Distinct protocols needed at various layers
• Network layer protocol secures link between
  wireless client, access point, base station or
  gateway
• Need complementary security mechanisms at higher
  protocol layers (Eg. WTLS in WAP)

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Outline

• Introduction
• Security Concerns
• Design Challenges
• Security Attacks on Smart Cards
• Masking Energy Behavior for DES Encryption

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Design Challenges

• Various challenges and considerations for mobile
  appliance security
• Flexible security architecture to support
  diverse security protocols and crypto algorithms
• Computational requirement for security processing
• Impact of security processing on battery life
• Tamper-resistant implementation

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Flexibility

• Ability to cater wide variety of security
  protocols
• Example Support for both WEP and 3GPP algorithms
  to work in LAN and 3G cellular environments
• Support for distinct security standards at
  different layers of network protocol stack
• Example WEP (link layer) and SSL (transport
  layer) support for wireless LAN enabled PDA with
  web support
• Security protocols continuously evolving
• Protocols revised to enable new security
  services, new crypto algorithms etc.

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Computational Requirements
Processing Requirements for a security protocol
using RSA based Connection 3DES based
encryption/decryption and SHA based integrity
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Battery life

• Reduced battery life due to increased
  computational requirements
• Case study Sensor node with Motorola Dragon Ball
  processor (MC68328)
• Energy Consumption
• Transmission 21.5 mJ/KB
• Reception 14.3 mJ/KB
• RSA based encryption
• 42mJ/KB

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Tamper-Resistance

• Security protocols and mechanisms are independent
  of implementation specifics
• Assumption being malicious entities do not have
  access to implementation
• Observing properties of the implementation can
  enable breaking of secret key
• Sensitive data is vulnerable
• During on-chip communication
• When simply stored in mobile appliance (secondary
  storage like flash, main memory, caches, register
  files)

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Outline

• Introduction
• Security Concerns
• Design Challenges
• Security Attacks on Smart Cards
• Masking Energy Behavior for DES Encryption

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Security Attacks on Smart Cards

• Security attacks on smart cards can be classified
  as
• Microprobing
• Invasive technique that manipulates the internal
  circuits
• Software attacks
• Focuses on protocol or algorithm weakness
• Eavesdropping
• Hacks secret keys by monitoring power
  consumption, EM radiation, and execution time
• Fault generation
• Based on intentional malfunction of the circuit
• Techniques like supply voltage change, exposing
  circuit to radiation etc.

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Eavesdropping power profile

• Rationale Power consumption of an operation
  depends on its operand values
• Operands are plain text and secret key in crypto
  algorithms
• Switching activity varies in memory, buses,
  datapath units, and pipeline registers based on
  operand values
• Different degrees of sophistication involved in
  power analysis based attacks
• Simple Power Analysis (SPA) uses single power
  profile
• Differential Power Analysis (DPA) uses power
  profiles from multiple runs

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Simple Power Analysis

• Based on single power trace for operations
• Identify operations being performed based on
  power profile
• Whether a branch is taken or not
• Whether an exponentiation operation is performed
  or not
• Knowing the algorithm and power profile, secret
  key can be revealed
• Protection from SPA
• Code restructuring
• Random noise insertion for power variation
• Adding dummy modules

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Differential Power Analysis

• Utilizes power profiles gathered from multiple
  runs
• Basic principle similar to SPA relies on data
  dependent power variation to break key
• Averaging used to eliminate random noises
• P.Kocher, J. Jaffer, and B. Jun Introduction to
  Differential Power Analysis and Related Attacks,
  http//www.cryptography.com/dpa/technical, 1998

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Outline

• Introduction
• Security Concerns
• Design Challenges
• Security Attacks on Smart Cards
• Masking Energy Behavior for DES Encryption

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Energy Masking for DES

• Architecture to have secure and non-secure
  instructions
• Power consumption for secure instructions data
  independent
• Critical operations in DES encryption
• Assignment
• Bit by bit addition modulo 2 (XOR)
• Shift operation
• Indexing operation
• Instructions involving secret key replaced with
  secure instructions

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Secure load instruction
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Energy consumption profiles
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Masking energy in DES

• Energy consumption more for secure instructions
  than non-secure instructions
• EDiss w/o masking 46.4 uJ
• EDiss w/ naïve masking 63.6 uJ (all loads and
  stores masked)
• EDiss w/ smart masking 52.6 uJ (only secret
  key related instructions masked)

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