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Policy-Guided Interactions in Ubiquitous Computing Systems
A Dissertation Prospectus
V. RamakrishnaAdvisor: Dr. Peter Reiher
Laboratory for Advanced Systems ResearchDepartment of Computer Science, UCLA
2
Proposal
Problem
Safe spontaneous interoperation in ubiquitous computing without pre-established trust relationships or rigid protocols
Solution
A generic and flexible negotiation protocol guided by local policy
3
Outline
Problem Introduction Proposed Solution System Research Issues Design Approach Research Plan Related and Complementary Research
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Problem Introduction
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Scenario – Web Service
Membership Request
News ServiceWeb Client
Your Name, Date of Birth, School, Email?
My Privacy Policy: Blah…blah…blah….
Why do I need to give up all this info?
I have NO TIME to read this list of policies, and I don’t know what
they mean!
Here’s all my info
Access GRANTED
Access REFUSED
Selected info
Come to think of it, I don’t really need all this
stuff he is promising!
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Scenario – Conference Room
PDA – CELL PHONE
PRIVILEGED ACCESSCOMMITTEE MEMBER
Internet
Require: Web access, Projector display, Printer.
Ring during emergency!
Allow display access to display only to attendees.Allow access to printer only to journal subscribers.No sound during presentations!Advertise journal!
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Scenario – Car on Freeway
Internet GPS
High bandwidth connection for streaming video
Identity info, credit card
Provide Internet Connection service.
Monitor traffic for the city.
WiMAX BASE STATION
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Motivations
Scenarios support limited ways of interaction Ubicomp scenarios will have more variations Rigid policies not desirable Cannot guarantee pre-established security
relationships Cannot enforce uniform interaction protocols
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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The Ubiquitous Computing Vision
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
Computing services everywhere and at any time
– Mark Weiser, 1991
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Ubicomp Goals and Characteristics
Internet
Home Network
Coffee ShopPHYSICAL INTEGRATION
SPONTANEOUS INTEROPERATION
No Milk !
Characteristics
Decentralized controlHeterogeneityAd hoc interactions
Personal Network
Location (GPS)
Video
Grocery Time !
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Ubicomp Research
Mature research areas• Seamless mobile networking
• Open systems and interfaces
• Smart space projects; e.g. Intelligent Room, GAIA
Not enough consideration given to• Bottom-up growth of infrastructure
• Security and privacy issues
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Ubicomp Interoperation
ALICE
BOB
Internet
Home Network
Coffee Shop
No Milk !Tell Alice.
Nature and Purpose
Discovery of external services Resource usage and access Intertwined processes of discovery and access control
Personal Network
GPS
Video
Grocery Time !
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
Device Network
Device Device
Connectivity?Location?Where is Bob?
Display Device?
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Barriers to Interoperation
Concerns• Security and privacy
• Dynamism and context changes
Roadblocks• Middleware and security frameworks do not scale
• Cannot force particular architectures or security preferences as standards
• Cannot guarantee pre-established security relationships
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Problems and Challenges
Hard problems• Match service demands to local resources within
policy constraints and context
• Reach flexible agreements in an automated fashion Challenges in a ubicomp environment
• Heterogeneous devices and communication features
• Diversity in resources possessed and exported
• Diversity in capabilities, desires and security policies
• Huge number of contexts and context-sensitive constraints that cannot be anticipated in advance
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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In Ubicomp Environments …..
Every device and every domain will not support every service or protocol
All pairs of computing entities will not be compatible
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Drawbacks in Existing Approaches
Based on rigid and static policies• Cannot resolve all conflicts
• Falls short of autonomic computing
Inadequate security and access control models• Scalability and flexibility issues
• Lack of support for non-identity based trust relationships
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Proposed Solution
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Service or application layer agreements
Based on policy Through a process of negotiation
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TCP/IPMAC
TCP/IP
Platform and Assumptions
TCP/IP
MAC
PHYSICAL
PHYSICALMAC
PHYSICAL
SEMANTIC WEB
APPLICATIONS
Internet /World Wide Web
Semantic Web
NEGOTIATION
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
(RDF/XML)
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Policy-Based Management
Policy describes state and desired behavior Governs all actions within bounded domains Wide expressive power Guides following system aspects
• Resource management
• Security and access control
• Context awareness
Interactions between domains• Discovery and access are the constants
• Policy is the only domain dependent variable
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Thesis Summary
Enable negotiation-driven interaction without:• Pre-established trust relationships
• Common set of service access protocols The negotiation protocol:
• Guided by local policy that constrains use and export of services
• Relies on common resource semantics
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Why Policy?
Minimum necessary for interaction and agreement
Why not specialized applications?• Difficult to make changes and to control
• Cannot anticipate all requirements and contexts
• Inter-modular dependencies difficult to handle
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Interaction through Negotiation
Bidirectional stateful protocol Strategic messaging Constant re-evaluation of goals Meta-policies and heuristics designed to
reach an agreement or compromise
A decentralized process of policy resolution and conflict management
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Negotiation model
D1 D2
R1
S1
P1
S2
R2
P2
Q1 R2 Q2 R1
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
Resources Applications Policies
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Scenario – Conference Room
PDA – CELL PHONE
PRIVILEGED ACCESSCOMMITTEE MEMBER
Internet
Require: Web access, Projector display, Printer.
Ring during emergency!
Allow display access to display only to attendees.Allow access to printer only to journal subscribers.No sound during presentations!Advertise journal!
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
REQUEST: Display; Web Access; Printer
PROOF: Committee Member
Sorry! I am just a Student Attendee
PERMISSION: Projector display, web accessOFFER: Journal membership for privileged access
POLICY: No sounds permitted!
OKI have ACM membership, as a UCLA student
OFFER: Privileged access
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Research Contributions
Interoperation approached top-down General purpose negotiation framework Context-sensitive access control Verification of security properties Non-intrusive and autonomic Enhances Panoply ubicomp middleware
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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System Research Issues
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Protocol Structure
Flexibility• Independent of application and domain
characteristics
• Identify a tight set of common objects and operations
• Only task for users – write high level policies Extensibility Strike a useful balance by experimenting
with characteristic applications
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Policy Language and Reasoning Engine
An expressive policy language Must be based on logic
• Support declarative cross-domain semantics
• Supports formal reasoning Must manage conflicts and maintain
consistency Support efficient indexing and retrieval
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Candidate Logical Framework
First order logic• Ontology includes objects and relationships
• Augment with deontic concepts
• Can be augmented (or restricted) to deal with contextual and trust parameters
• Reasoning framework and querying algorithms
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Security Aspects Key research aspects
• Security benefits to ubicomp• Secure negotiation protocol from compromise
Security benefits• Concerns proper use of security mechanisms rather than
propose new ones• Promotes a paradigm that ensures safety is taken into
consideration before interaction• Allows static and dynamic detection of security conflicts
Protocol security• Cryptographic mechanisms, SSL, TLS• Can the nature of the protocol itself be used to compromise
security?
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Trust and Access Control Access control framework targets
• Scalability and flexibility• Based on a general notion of trust
Trust model• Based on identity, provable relationships, properties and
actions• Domain and application independent• Provides heuristics to compare among choices and make
negotiation decisions Negotiation is a way of doing fine-grained,
dynamic and context-sensitive access control Can be used to build webs of trust
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Negotiation Strategies and Heuristics
Negotiation protocol• Series of messaging rounds
• Directed towards a perceived goal
• Strategies to choose among various options• Eager and lazy: two extreme ends
Heuristics as decision-making aid• Compute and re-evaluate goals
• Must work within policy constraints extrapolated to the current context
• Use trust and utility functions
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Theoretical Aspects
Correctness Completeness Optimality
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System Design Issues
Resource management, interfaces and access mechanisms
Context Awareness Performance Fault tolerance and reliability Working with low capability devices and
networks Negotiation with legacy devices and software
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Design, Implementation and Evaluation
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Panoply Ubicomp Infrastructure
Middleware for ubiquitous computing Building and management of device
communities (spheres of influence) Spheres of influence
• Boundaries around sets of devices and resources
• Criteria could be geography (physical location, common LAN), tasks, social group
• Scopes policy, which guides interactions
• Communication based on an event model
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Panoply Architecture
PANOPLY MIDDLEWARE
SPHERE MANAGER
APPLICATIONS
OPERATING SYSTEM
NETWORK
POLICY MANAGER
MyResearch
Associated Research
External Components
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Policy Manager - Functional View
Messaging Interface (To other system components, remote computers)
Policy Database
FRONT END
CONTROLLER
POLICY ENGINE
Knowledge engineering Mechanisms (Forward Chaining, Backward Chaining,
Conflict Resolution, etc.)
Heuristics/Metrics Security/Trust ModelSemantic Interpretation
of Messages
Protocol State Machine
Message Multiplexer/De-multiplexer
Event Listener
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Negotiation Protocol
Minimal number of message types• Requests
• Offers
• Policies
Protocol state machine• Based on message types
• Independent of message content
• Content interpreted by lower layers
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Policy Model
Prolog used for writing policies• Subset of first order logic
• Declarative syntax
• Fast algorithms for logical reasoning
State information and rules written as predicates• Designated predicates for high-level understanding
• External functions (Java) for non-logical tasks
Develop richer ontology
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Current Negotiation Model
Security model• Permit actions or accesses in a conservative
manner
Negotiation goals and strategies• Fixed goals and alternatives
• Fixed strategy, based on satisfaction of relevant policies
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Future Models
Trust model• Use advanced RBAC mechanisms
• Trust levels for comparison of alternatives
Negotiation strategy• Heuristics that allow risk-benefit analysis
• Use game-theoretic notions
• Utility model than can infer and compare utilities of objects and actions
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Implementation
Policy Manager• Implemented in Java
• Policy Engine based on SWI-Prolog Description of entities, resources and
properties• XML and RDF
Security mechanisms• X.509 certificates
• Panoply vouchers
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Current Status Basic policy manager implemented
• Front end• Implements protocol state machine• Supports multiple threads
• Policy engine• Query the policy database• Add, remove and replace statements
• Controller• Adopts simple, cautious negotiation strategy• Requests, offers and checks for alternatives
Integrated within a Panoply sphere• Uses events for negotiation and to obtain and update state information
Principal task performed: Negotiate for membership within a sphere
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Research Plan
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Basic Policy Manager and Evaluation
Experiment with policy manager within the Panoply context• Performance evaluations
• Overhead measurements
• Scalability
• Explore benefits through applications• Location sensitive interactive fiction
• LACMA gallery experience
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Modeling Issues
Policy Language and Reasoning Engine Trust Model Resource Utility Model Negotiation Strategy and Heuristics
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Complete Policy Manager
Incorporate models into negotiation heuristics• Enhance controller with strategic decision
making capability
Augment spheres by adding• Resources and services
• Context sensors
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Analysis and evaluation
Generate real ubicomp scenarios Theoretical Analysis
• Correctness and completeness
• Efficacy of strategies
Performance Evaluations• Overhead measurements
• Scalability with respect to
• Policy database size
• Multi-session load
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Evaluation of Success
Success of strategies and heuristics• Compare initial set of requirements or desires
with the final result
• Compare final result with optimal result
Security benefits• Amount of risk taken, or compromises made
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Dissertation Timeline
Milestone Completion Date
Basic Policy Manager July 2005
Evaluation of Basic Policy Manager November 2005
Policy Language Enhancements December 2005
Security, Trust and Utility Models March 2006
Generalized Policy Manager May 2006
Evaluation of Generalized Policy Manager August 2006
Optimizations October 2006
Writing Dissertation March 2007
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Related and Complementary Research
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Research Areas
Negotiation Protocols Policy Languages Ubiquitous Interoperation Middleware Access Control and Trust
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Protocols and Languages Negotiation protocols
• Automated trust negotiation• Goal: client-server transactions on the web• Conflicts result in failure• TrustBuilder [BYU,UIUC], PeerTrust
• Service level negotiations in grid computing• SNAP [ISI]
Policy languages• Rei pervasive computing language
• Cross-application semantics• Deontic concepts
• Trust negotiation languages – PSPL, Keynote• XML-based web access control – XACML, TPL [IBM]
Semantic web ontology – DAML+OIL, OWL, SOUPA
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Service Discovery and Access Control Frameworks Middleware for open systems
• Ubicomp active space middleware – Hyperglue [MIT], Cerberus [UIUC]
• Service discovery – JINI, UPnP• Limited security features
Access Control• Advanced Role-Based Access Control Models
• Generalized RBAC• Dynamic RBAC
Trust frameworks• SECURE project
• Dynamic notion of trust• Trust evolution based on interaction history
• Reputation frameworks
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Conclusion Existing means of interoperation are too rigid
and unsuitable for ubicomp Identify flexible policy as the minimum
requirement Negotiation can be automated using logic-
based policy, trust and utility models Applications can rely on the underlying system
to discover and access external resources with minimal risk and adjusting with context
Promote a security-oriented approach towards the design of intelligent spaces
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Thank YouThank You
Relevant publications:
Kevin Eustice, Leonard Kleinrock, Shane Markstrum, Gerald Popek, V. Ramakrishna and Peter Reiher, “Enabling Secure Ubiquitous Interactions,” In the proceedings of the 1st International Workshop on Middleware for Pervasive and Ad-Hoc Computing (in conjunction with Middleware 2003), 17th June 2003 in Rio de Janeiro, Brazil.
K. Eustice, L. Kleinrock, S. Markstrum, G. Popek, V. Ramakrishna and P. Reiher, "Securing WiFi Nomads: The Case for Quarantine, Examination, and Decontamination," Proceedings of the New Security Paradigms Workshop (NSPW), 2003.
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Conclusion Existing means of interoperation are too rigid
and unsuitable for ubicomp Identify flexible policy as the minimum
requirement Negotiation can be automated using logic-
based policy, trust and utility models Applications can rely on the underlying system
to discover and access external resources with minimal risk and adjusting with context
Promote a security-oriented approach towards the design of intelligent spaces
60
Security Aspects Key research aspects
• What security benefits does a negotiation protocol provide to a system offering ubiquitous services?
• How do we secure the negotiation protocol itself from being compromised?
Security benefits• Concerns proper use of security mechanisms rather than propose
new ones• Promotes a paradigm that ensures safety is taken into
consideration before interaction• Allows static and dynamic detection of security conflicts
Protocol security• Cryptographic mechanisms, SSL, TLS• Can the nature of the protocol itself be used to compromise
security?
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Research Issues
Policy Expression and Reasoning Security and Trust Model Negotiation Heuristics and Strategies Theoretical Issues Systems Issues
• Protocol flexibility and extensibility
• Performance
• Fault tolerance and reliability
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Thesis Proposal
A generic and flexible negotiation protocol guided by local policy through which devices and domains in ubicomp can interoperate spontaneously
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Outline First slide – one line summary of the problem I am tackling Ubicomp vision
• What has been done• How it has been done• What is missing, or what needs to be seriously improved; i.e. motivation
My approach at a very high level, with the assumptions I make about the world Everything about policy
• How policy is useful in ubicomp situations• Domain-oriented view of world• Different categories of policies• Potential for conflicts with large number of policies, and the need for expressiveness, domain-independence,
well-defined semantics and reasoning mechanisms Negotiation as a model for interactions Examples:
• Starbucks: current (simple model); then, with negotiation• Another example: maybe the home video example
List of benefits/research contributions Research issues Current design and implementation status Research plan and timeline Conclusion
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Scenario
Bob’s PDA DHCP Protocol
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Scenario
REQUEST: Join networkREQUEST: High bandwidth connection
REQUEST: Printer access
Bob’s PDA
(YES): Join network, get requested services
DEMAND: Email addressDEMAND: Accept pop-ups
(NO): No connectivity
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
66
Ubicomp Interoperation
Nature and purpose of interoperation• Discovery of external services
• Access and usage of resources and data
• Service discovery and access control intertwined
Typical interactions• Mobile devices and wireless networks
• Direct communication between two devices
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Assumptions
Common networking capability Common understanding of objects at the
application layer• Leverage Semantic Web research
• Common syntax, or annotations, using XML
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Negotiation Model
Initial state• Each entity has a set of resources, policies and initial
requirements
Communication protocol• Exchange of messages that results in a maximal
satisfaction of requirements as constrained by the policies
• Messages include requests, offers, policy rules
• Bi-directional protocol (after initial message)
• Stateful protocol
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Scenario
Join network, need ‘x’ bandwidth
Offer ‘y’ < ‘x’, OR ask for private info (email)
Bob’s PDA
Certificates?, Privacy Policy?
Private info
Certificates, Privacy Policy, Preferred Member incentive
Join permission (network configuration info), proxy info, Preferred Member voucher
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Programming Languages
Artificial IntelligenceOperating Systems
My Research
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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More Issues
Systems Issues• Performance (fast retrieval, fast path)
• Resource description and management
• Fault tolerance and reliability
• Scale to multi-party negotiation
• Context awareness
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Beyond 2-party Negotiation
Multi-session negotiation• (1 n) negotiation
• Handle dependencies among multiple sessions
• Scalability issues Multi-party negotiation
• (n n) negotiation
• Similar dependency issues
• Additional distributed systems problems
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Negotiation Protocol State Machine
START
EXPECT
INITIATE
SERVICE PROCESS
STOP
Trigger/Event toStart Negotiation
Send REQUEST(S)
Receive REQUEST(S)
Receive REQUEST(S)
Send REQUEST(S) / OFFERS(S) / POLICIES
Send REQUEST(S) / OFFERS(S) / POLICIES
ReceiveOFFERS(S) / POLICIES
ReceiveOFFERS(S) / POLICIES
ReceiveTERMINATE Signal /
TIMEOUT
SendTERMINATE Signal
SendTERMINATE Signal
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Implementation
Policy manager implemented in Java Prolog used for writing policies
• Subset of first order logic
• Declarative syntax
• Fast algorithms for logical reasoning Policy Engine based on SWI-Prolog
• Java-Prolog and Prolog-Java APIs
• Open source
• Meta-predicates
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Implementation (continued)
Description of entities, resources, properties
• XML and RDF Trust and Access Control Models
• Advanced RBAC models Negotiation goals and strategies
• Fixed goals and alternatives
• Fixed strategy, based on satisfaction of relevant policies
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Current Status
Minimal policy manager almost done• Negotiation protocol state machine
• Policy engine mechanisms to run queries and return state and policy info
• Controller negotiates by sending requests and counter requests to till success/no progress is possible
Next step – testing with Panoply spheres
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System Optimizations and Enhancements
Design modifications and enhancements based on observed performance• Fast path for quick decision making
• Emphasis on strategy that guarantees results in real time
Multi-session negotiation• Investigate inter-thread dependencies
• Investigate scaling properties of currently used reasoning algorithms
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Related Work Automated trust Negotiation
• Sequence of credential exchanges that result in access granted/rejected for a resource
• Meant for web transactions / not for dynamic environments like ubicomp
Policy Languages• Mostly application specific• Rei – targeted for pervasive computing
Access Control Models• Certificates/Delegations• Generalized RBAC
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Negotiation Protocols Automated trust negotiation
• Goal: client-server transactions on the web• Builds up proof of access through progressive
exchange of credentials• Conflicts result in failure• Examples: TrustBuilder [BYU,UIUC], PeerTrust
Service negotiation in grid computing• A decentralized framework for dynamic resource
allocation• Typically neglects security concerns• Example: SNAP [ISI]
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Policy Languages Rei policy language
• Specially targeted towards pervasive computing and the semantic web
• Defined cross-application semantics• Incorporates deontic concepts like obligations and
permissions Trust negotiation languages
• Portfolio and Service Protection Language (PSPL)• KeyNote
Languages for access control on the web (XML-based)• Limited in expressiveness and support for negotiation• Examples: XACML, IBM’s TPL
Ontology for the semantic web• DAML+OIL, OWL, SOUPA
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Ubiquitous Middleware
Active Space projects
• Examples: Hyperglue, Cerberus, Centaurus 2
• Generally manage resources and are context-sensitive
• Limited security and access control features Service discovery frameworks
• Examples: Jini, UPnP
• Emphasis on open interfaces and easy interoperation rather than security
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Access Control and Trust ACLs and capabilities
• Not scalable or usable in dynamic conditions Role-based Access Control
• Not very flexible• Generalized RBAC (GRBAC)• Dynamic RBAC (dRBAC)
Trust• Fairly well-accepted concept in ubicomp• PolicyMaker
• Credentials tied to permissions rather than identity
• SECURE project• Dynamic notion of trust• Trust evolution based on interaction history
• Reputation frameworks
Introduction – Solution – Research Issues – System Design – Research Plan – Related Work
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Conclusion
Spontaneous ubiquitous interoperation poses many challenges• Mechanisms exist, but no frameworks
Flexible process of reaching agreements through negotiation• Policy management is the core
• Trust and utility models Existing research
• Fails to address problem in its entirety, or
• Produces domain-specific solutions
