Security and PDAs in Mobile Computing Environments

1
Security and PDAs in Mobile Computing Environments

• By Loo Tang Seet
• and
• Camilla Fjortoft

2
Today we will talk about

• PDAs and their characteristics
• Security requirements
• Advantages and Limitations
• Operating Systems
• Authentication Authorization (AA) in Mobile
  Computing Environments
• AA in Mobile Computing environment
• Charon Architecture
• Tiny SESAME Architecture

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Personal Digital Assistants (PDAs)

• Small, smaller, smallest
• View, store and transmit data from a handheld
  device
• New applications
• FiloFax or Business/Enterprise applications?
• Mix of personal and business data
• Less personal
• Access and store corporate data

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PDAs cont..

• Extremely portable, huge advantage
• Can be used as an access control device by a
  wireless network
• The access to the device must be controlled
• This control must be greater than that for your
  PC
• Constitute Availability, Confidentiality and
  Integrity of data

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Threats

• Small, easy to run-away-with, forget, lose..
• Removable memory card with data
• Wireless communication
• IR,
• data is being beamed to another device
• via the IR port
• Wireless network access points
• Virus
• Synchronizing with Host PC
• Email attachments

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Threats cont..

• Operating System
• Four to seven digit PIN for accessing the device
• Single user access
• Input methods
• I.e. by pen, choose simple passwords
• Not all OS have support for data to be encrypted,
  need third party software ? power consumption

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Security Requirements

• Secure access to device, data and network
• Encryption of data
• The device,or data, cannot be tampered with
• OS integrity and file system security
• Protection against virus and malicious code
• Sufficient power supply and memory
• Security policy involving handheld devices

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Limitations of PDAs

• Power
• Battery only lasts for couple of hours when
  connected to wireless network
• Reduces the amount of time to run applications
• Power is a major limitation
• Processing speed
• Good enough for cryptographic operations
• Memory
• Memory no longer a limitation for new PDAs. Can
  get micro drivers with several GB of capacity

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Operating Systems

• Windows CE
• 4 to 7 digit PIN, accessible by others
• No support for data to be encrypted
• Need third party software
• Larger power consumption
• PalmOS
• For devices with restricted resources
• Password for accessing the device
• Single user OS, no file access based on user
  identity
• Linux
• Many different distribution available

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PDA survey
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Authentication Authorization in Mobile
Computing Environments
Tiny SESAME
Charon
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Overview

• Authentication authorization issues in mobile
  computing environments
• Existing authentication and authorization
  security architectures
• Adapting existing security architectures to
  mobile computing environments
• Conclusions

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Authentication authorization Issues in Mobile
Computing Environment

• Two constraints presented by mobile computing
  environment
• Processing resource constraints on the mobile
  platform
• Communication resource constraints in the mobile
  network
• Two approach to providing AA for mobile
  computing environment
• adapting existing security architecture or
• design a whole new architecture

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Existing AA Security Architectures

• Kerberos
• Developed by MIT for Project Athena
• Provides end-to-end mutual authentication between
  client and server with single sign on
• Authorization is provided by the host OS
• SESAME
• An extension to Kerberos with additional services
• Provides both authentication and authorization
  services and delegation of access rights
• Supports both password and public key
  authentication
• Supports RBAC

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Charon Indirect Authentication Using Kerberos
IV by UC at Berkeley

• Migrating Kerberos into mobile computing platform
• Displacing complexity from client to proxy
• Only DES encryption/decryption on the client
• Kerberos library shifted to proxy
• Rewrites client and libdes library to run on the
  Sony MagicLink PDA with a total footprint of
  45kB ( 9 of the original size of kinit)
• No modification to KDC and server is required

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Charon Architecture
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Charon Architecture
Phase II Obtaining ticket for proxy
Kerberos
Client
AS
5,9
Proxy
6
8
TGS
7
Service
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Charon Architecture
Phase III Accessing a Service via Proxy
Kerberos
Client
10,14
AS
Proxy
11
13
TGS
12
15
16
Service
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Charon vs Standard Kerberos

• Inherits both the strength and shortcomings of
  Kerberos IV
• Charon provides a lightweight client to
  accommodate the mobile computing devices with
  limited storage space
• Additional protocol exchanges required to
  establish trust between client and proxy
• No network performance advantage using Charon
  versus the unmodified Kerberos

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Adapting PKINIT - By A. Harbitter D.
Menasce

• PKINIT Public key extension to Kerberos V
  initial authentication phase
• Public key encryption requires more computational
  resources
• General approaches to adapt PK based security
  systems
• Reduce the number of public/private key
  operations on the mobile client side
• Choose the right public key algorithm that allows
  faster public/private key operation to be
  performed on the mobile client side (refer to
  next slide)
• Use proxy to offload some processing from client

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Relative Speeds of Public/Private Key Operations
Using DSA and RSA
Refer to Applied Cryptography, by Bruce Schneier
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TINY SESAME - By UIUC

• A lightweight SESAME implemented in Java using
  component-based architecture
• Supports authentication, simple encryption,
  integrity checks and RBAC
• Dynamic component loading

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Tiny SESAME Architecture
Client Side
Security Server
AS
APA Client
PAS
KDS
GSS-API
DCL
SACM
Communication Protocol
Security Context
Application Server
APA-Client Authentication Privilege
client. AS Authentication Server. DCL
Dynamic Component Loader. GSS Generic
Security Services. KDS Key Distribution
Center. PAC Privilege Attribute
Certificate. PAS Privilege Attribute
Server. PVF PAC Validation Facility. SACM
Secure Association Context Manager.
DCL
SACM
GSS-API
PVF
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Conclusions

• Current AA security architectures trust the
  client to protect confidential keying information
• PDAs are becoming less personal
• PDA are small, portable and easily subverted
• Better security is needed for PDA