Pervasive Computing

UNIT I

Introduction

Our life in the future should be very carefree with little to no hassle.

Less searching, more fast and accurate access to information, when needed.

Time and location boundaries will eventually be eliminated, resulting in a true information age style of

civilisation.

Future devices will become more and more intelligent , they will start to talk among themselves to serve

as better.

Introduction

Ubiquitous - Present Everywhere

Bringing mobile, wireless and sensor networking technologies together towards a new computing

paradigm

Everywhere, anywhere, always on, anytime

Introduction

Pervasive computing is the third wave of computing technologies to emerge since computers first

appeared:

• First Wave - Mainframe computing era: one computer shared by many people, via workstations.

• Second Wave - Personal computing era: one computer used by one person, requiring a conscious

interaction. Users largely bound to desktop.

• Third Wave – Pervasive (initially called ubiquitous) computing era: one person, many computers. Millions

of computers embedded in the environment, allowing technology to recede into the background

The Third Wave of Computing

Dramatic calm

Obtrusive inconspicuous

Overpowering empowering

Distracting facilitating

Difficult easy

Extraordinary everyday

Complex simple

Desktop embedded interface

Introduction

The aim of ubiquitous computing is to design computing infrastructures in such a manner that they

integrate seamlessly with the environment and become almost invisible.

Ubiquitous computing vision

Introduction

Unobtrusiveness and Spread through

From all the directions

Degree of Penetration

Our physical world is Pervasive, because it surrounds us all the time.

This is a collection of nature and things.

Principles of Pervasive Computing

“The most profound technologies are those that dissappear. They weave themselves into the fabric of

everyday life until they are indistinguishable from it.”

Creation of environments saturated with computing and communication capability, yet gracefully

integrated with human users.

Scientific American,

Vol. 265 N.9, pp. 66-75, 1991

Principles of Pervasive Computing

During one of his talks, Weiser outlined a set of principles describing pervasive computing (also called

ubiquitous computing):

The purpose of a computer is to help you do something else.

The best computer is a quiet, invisible servant.

The more you can do by intuition the smarter you are; the computer should extend your unconscious.

Technology should create calm.

Calm technology

“A technology that which informs but doesn't demand our focus or attention”.

(Designing Calm Technology, Weiser and John Seeley Brown)

Yesterday's Computers Filled Rooms …

… So Will Tomorrow’s

Principles of Pervasive Computing

Pervasive computing integrates computation into the environment, rather than having computers which

are distinct objects.

Other terms for pervasive computing:

Ubiquitous computing

Calm technology

Things that think

Everyware

Pervasive internet

Ambient intelligence

Proactive computing

Augmented reality

Ubiquitous computing

Ubiquitous computing (ubicomp) integrates computation into the environment, rather than having

computers which are distinct objects. Promoters of this idea hope that embedding computation into the

environment and everyday objects would enable people to interact with information-processing devices

more naturally and casually than they currently do, and in ways that suit whatever location or context

they find themselves in.

Ubiquitous computing encompasses wide range of research topics, including distributed computing,

mobile computing, sensor networks, human-computer interaction, and artificial intelligence.

Sentient computing

Sentient computing is a form of ubiquitous computing which uses sensors to perceive its environment

and react accordingly. A common use of the sensors is to construct a world model which allows

location-aware or context-aware applications to be constructed.

One famous research prototype of a sentient computing system was the work at AT&T Laboratories,

Cambridge (now defunct). It consisted of an ultrasonic indoor location system called the “Active Bats”

which provided a location accuracy of about 3 cm. The world model was managed via the SPIRIT

database, using CORBA to access information and spatial indexing to deliver high-level events such as

“Alice has entered the kitchen” to listening context-aware applications. The research continues at the

Digital Technology Group at the University of Cambridge.

Some example applications of the system include:

A “follow-me phone” which would cause the telephone nearest the recipient to ring.

Teleporting desktops via VNC just by clicking their Active Bat near the computer.

Spatial buttons which were activated by clicking the Active Bat at a particular spot (such as a poster).

Measuring and surveying buildings.

Locative games

Context adaptative computing

Context adaptative computing

A context adaptive system typically enables the user to maintain a certain application (in different forms)

while roaming between different wireless access technologies, locations, devices and even

simultaneously executing everyday tasks like meetings, driving a car etc.

For example a context adaptive and hence ubiquitous navigation system would offer navigation support

in the situations at home, indoor, outdoor, and in car.

This involves making the navigation functionality available for different availability of output devices,

input devices and location sensors as well as adapting the user interaction operability to the current

speed, noise or operator handicaps while keeping in mind the overall applicability depending on the user

preferences, his knowledge, current task etc.

Wearable computers

Wearable computers are computers that are worn on the body. They have been applied to areas such as

behavioral modeling, health monitoring systems, information technologies and media development.

Government organizations, military, and health professionals have all incorporated wearable computers

into their daily operations. Wearable computers are especially useful for applications that require

computational support while the user’s hands, voice, eyes or attention are actively engaged with the

physical environment.

One of the main features of a wearable computer is consistency. There is a constant interaction between

the computer and user, ie. There is no need to turn the device on or off. Another feature is the ability to

multi-task. It is not necessary to stop what you are doing to use the device; it is augmented into all other

actions. These devices can be incorporated by the user to act like a prosthetic. It can therefore be an

extension of the user’s mind and/or body.

Examples for wearable computers: calculator watch ,EyeTap,Head-mounted display ,

Head-up display,Laptop,Personal digital assistant,Tablet PC,Virtual retinal display

Context-aware pervasive systems

Context-aware pervasive systems (or aware systems, for short) refer to systems that can be aware of

their physical (and virtual) environment or situation, and respond intelligently based on such awareness.

It is among the most exciting trends in computing today, fueled by developments in pervasive computing,

including new computers worn by users, embedded devices, sensors, and wireless networking technology

Ambient Intelligence

The concept of ambient intelligence or AmI is a vision where humans are surrounded by computing

and networking technology unobtrusively embedded in their surroundings. See also ubiquitous

computing.

The concept of ambient intelligence (AmI) was developed by the ISTAG advisory group to the European

Commission’s DG Information Society and the Media. AmI puts the emphasis on user-friendliness,

efficient and distributed services support, user empowerment, and support for human interactions. This

vision assumes a shift away from PCs to a variety of devices which are unobtrusively embedded in our

environment and which are accessed via intelligent interfaces.

In order for AmI to become a reality a number of key technologies are required:

Unobtrusive hardware (miniaturisation, nano-technology, smart devices, sensors etc.)

A seamless mobile/fixed web-based communication infrastructure (interoperability, wired and wireless

networks etc.)

Dynamic and massively distributed device networks

Natural feeling human interfaces (intelligent agents, multi-modal interfaces, models of context awareness

etc.)

Dependability and security (self-testing and self repairing software, privacy ensuring technology etc)

Urban computing

urban computing: the integration of computing, sensing, and actuation technologies into our everyday

urban settings and lifestyles. Successful integration requires taking several facets of the urban

environment into account at once.

Urban settings frame social behaviors; they encompass architectural forms and features that may or may

not be harmonious with given technologies; and they are increasingly but variably permeated by wireless

networks and fixed and mobile devices.

A key challenge is the great diversity and density of people, devices, and built artifacts found in urban

places.

Urban computing ranges from city-wide transportation-sensing infrastructure, to services embedded in a

cafe, to the bluetooth “aura” of an individual’s mobile phone as he or she walks down a street.

Principles of Pervasive Computing

Central aim of pervasive computing: invisibility

One does not need to continually rationalize one's use of a pervasive computing system.

Having learnt about its use sufficiently well, one ceases to be aware of it.

It is "literally visible, effectively invisible" in the same way that a skilled carpenter engaged in his

work might use a hammer without consciously planning each swing.

Similarly, when you look at a street sign, you absorb its information without consciously performing

the act of reading.

Pervasive

The essence of that vision was the creation of environments saturated with computing and

communication capability, yet gracefully integrated with human users.

Pervasive – all around us

Should be there where we need them

Not go and get them

Human Centered

Computers should adapt to the humans

Computations enter our world

Must be unobtrusive and minimize user distraction

Computers as we know it will disappear

Better ways of Computer-Human interaction

The computers need to be aware of humans – Context

Pervasive Environment

The most important characteristics of pervasive environments are:

Heterogeneity: Computing will be carried out on a wide spectrum of client devices, each with different

configurations and functionalities.

Prevalence of "Small" Devices: Many devices will be small, not only in size but also in computing

power, memory size, etc.

Limited Network Capabilities: Most of the devices would have some form of connection. However,

even with the new networking standards such as GPRS, Bluetooth, 802.11x, etc., the bandwidth is still

relatively limited compared to wired network technologies. Besides, the connections are usually unstable.

High Mobility: Users can carry devices from one place to another without stopping the services.

User-Oriented: Services would be related to the user rather than a specific device, or specific location.

Highly Dynamic Environment: An environment in which users and devices keep moving in and out of

a volatile network.

Future of Pervasive Computing

Evolution

Distributed Computing

intersection of personal computers and local area networks.

Mobile Computing

The appearance of full-function laptop computers and wireless LANs in the early 1990s led

researchers to confront the problems that arise in building a distributed system with mobile clients.

The field of mobile computing was thus born.

Distributed Computing

Remote communication, including protocol layering, remote procedure call, the use of timeouts, and the

use of end to- end arguments in placement of functionality

Fault tolerance, including atomic transactions, distributed and nested transactions, and two-phase

commit

High availability, including optimistic and pessimistic replica control, mirrored execution, and optimistic

recovery

Remote information access, including caching, function shipping, distributed file systems, and distributed

databases

Security, including encryption-based mutual authentication and privacy

Mobile Computing – Key Constraints

unpredictable variation in network quality,

lowered trust and robustness of mobile elements,

limitations on local resources imposed by weight and size constraints, and concern for battery power

consumption

Mobile Computing

Mobile networking, including Mobile IP, ad hoc protocols, and techniques for improving TCP

performance in wireless networks

Mobile information access, including disconnected operation, bandwidth-adaptive file access, and

selective control of data consistency

Support for adaptative applications, including transcoding by proxies and adaptive resource management

System-level energy saving techniques, such as energy-aware adaptation, variable-speed processor

scheduling, and energy-sensitive memory management

Location sensitivity, including location sensing and location-aware system behavior

Effective Use of Smart Spaces

The first research thrust is the effective use of smart spaces. A space may be an enclosed area such as a

meeting room or corridor, or a well-defined open area such as a courtyard or quadrangle.

By embedding computing infrastructure in building infrastructure, a smart space brings together two

worlds that have been disjoint until now. The fusion of these worlds enables sensing and control of one

world by the other.

Invisibility

The second thrust is invisibility. The ideal expressed by Weiser is complete disappearance of pervasive

computing technology from a user’s consciousness. In practice, a reasonable approximation to this ideal

is minimal user distraction.

If a pervasive computing environment continuously meets user expectations and rarely presents him with

surprises, it allows him to interact almost at a subconscious level

Localized Scalability

The third research thrust is localized scalability. As smart spaces grow in sophistication, the intensity of

interactions between a user’s personal computing space and his/her surroundings increases. This has

severe bandwidth, energy, and distraction implications for a wireless mobile user.

The presence of multiple users will further complicate this problem. Scalability, in the broadest sense, is

thus a critical problem in pervasive computing.

Previous work on scalability has typically ignored physical distance — a Web server or file server should

handle as many clients as possible, regardless of whether they are located next door or across the country.

The situation is very different in pervasive computing.

Here, the density of interactions has to fall off as one moves away; otherwise, both the user and his

computing system will be overwhelmed by distant interactions that are of little relevance.

Masking Uneven Conditioning

The fourth thrust is the development of techniques for masking uneven conditioning of environments.

The rate of penetration of pervasive computing technology into the infrastructure will vary considerably

depending on many nontechnical factors such as organizational structure, economics, and business

models. Uniform penetration, if it is ever achieved, is many years or decades away.

In the interim, there will persist huge differences in the “smartness” of different environments — what is

available in a well-equipped conference room, office, or classroom may be more sophisticated than in

other locations. This large dynamic range of “smartness” can be jarring to a user, detracting from the goal

of making pervasive computing technology invisible.

Evolution & Related Fields

Other related fields:

Sensor Networks

A sensor network consist of a large number of tiny autonomous computing devices, each equipped

with sensors, a wireless radio, a processor, and a power source.

Sensor networks are envisioned to be deployed unobtrusively in the physical environment in order

to monitor a wide range of environmental phenomena (e.g., environmental pollutions, seismic

activity, wildlife) with unprecedented quality and scale.

Evolution & Related Fields

Other related fields:

Human Computer Interaction

HCI is the study of interaction between people (users) and computers.

A basic goal of HCI is to improve the interaction between users and computers by making

computers more user-friendly and receptive to the user's needs.

A long term goal of HCI is to design systems that minimize the barrier between the human's

cognitive model of what they want to accomplish and the computer's understanding of the user's

task.

Evolution & Related Fields

Other related fields:

Artificial Intelligence

AI can be defined as intelligence exhibited by an artificial (non-natural, manufactured) entity.

AI is studied in overlapping fields of computer science, psychology and engineering, dealing with

intelligent behavior, learning and adaptation in machines, generally assumed to be computers.

Research in AI is concerned with producing machines to automate tasks requiring intelligent

behavior.

Problem Space

Design and implementation problems in pervasive comp.

User intent

Cyber foraging

Adaptation strategy

High-level energy management

Client thickness

Context awareness

Balancing proactivity and transparency

Impact on layering

Privacy and trust

Problem Space

User intent

For proactivity to be effective, it is crucial that a pervasive computing system track user intent.

Otherwise, it will be almost impossible to determine which system actions will help rather than hinder

the user.

For example, suppose a user is viewing video over a network connection whose bandwidth suddenly

drops. Should the system:

Reduce the fidelity of the video?

Pause briefly to find another higher-bandwidth connection?

Advise the user that the task can no longer be accomplished?

The correct choice will depend on what the user is trying to accomplish.

Problem Space

Cyber foraging (also called “living off the land”)

The idea is to dynamically augment the computing resources of a wireless mobile computer by

exploiting wired hardware infrastructure.

As computing becomes cheaper and more plentiful, it makes economic sense to “waste” computing

resources to improve user experience.

In the forseeable future, public spaces such as airport lounges and coffee shops will be equipped with

compute servers or data staging servers for the benefit of customers, much as table lamps are today.

(Today, many shopping centers and cafeterias offer their customers free wireless internet access.)

Problem Space

Adaptation strategy

Adaptation is necessary when there is a significant mismatch between the supply and demand of a

resource (e.g. wireless network bandwidth, energy, computing cycles or memory).

There are three alternative strategies for adaptation in pervasive computing:

A client can guide applications in changing their behavior so that they use less of a scarce resource.

This change usually reduces the user-perceived quality, or fidelity, of an application.

A client can ask the environment to guarantee a certain level of a resource (reservation-based QoS

systems). From the viewpoint of the client, this effectively increases the supply of a scarce resource

to meet the client’s demand.

A client can suggest a corrective action to the user. If the user acts on this suggestion, it is likely

(but not certain) that resource supply will become adequate to meet demand.

Problem Space

High-level energy management

Sophisticated capabilities such as proactivity and self-tuning increase the energy demand of software

on a mobile computer in one’s personal computing space.

Making such computers lighter and more compact places severe restrictions on battery capacity, so

the higher levels of the system must be involved in memory management.

One example is energy-aware memory management, where the operating system dynamically controls

the amount of physical memory that has to be refreshed.

Another example is energy-aware adaptation, where individual applications switch to modes of

operation with lower fidelity and energy demand under operating system control.

Problem Space

Client thickness (hardware capabilities of the client)

For a given application, the minimum acceptable thickness of a client is determined by the worst-case

environmental conditions under which the application must run satisfactorily.

A very thin client suffices if one can always count on high-bandwidth low-latency wireless

communication to nearby computing infrastructure, and batteries can be recharged or replaced easily.

If there exists even a single location visited by a user where these assumptions do not hold, the client

will have to be thick enough to compensate at that location.

This is especially true for interactive applications where crisp response is important.

Problem Space

Context awareness

A pervasive computing system must be cognizant of its user’s state and surroundings, and must

modify its behavior based on this information.

A user’s context can be quite rich, consisting of attributes such as physical location, physiological

state (e.g., body temperature and heart rate), emotional state (e.g., angry, distraught, or calm), personal

history, daily behavioral patterns, and so on.

If a human assistant were given such context, he or she would make decisions in a proactive fashion,

anticipating user needs.

In making these decisions, the assistant would typically not disturb the user at inopportune moments

except in an emergency.

A pervasive computing system should emulate such a human assistant.

Problem Space

Balancing proactivity and transparency

Unless carefully designed, a proactive system can annoy a user and thus defeat the goal of invisibility.

A mobile user’s need and tolerance for proactivity are likely to be closely related to his/her level of

expertise on a task and familiarity with his/her environment.

A system that can infer these factors by observing user behavior and context is better positioned to

strike the right balance.

For transparency, a user patience model can be implemented to predict whether the user will respond

positively to a fetch request. So the user interaction is suppressed and the fetch is handled

transparently.

Problem Space

Impact on layering

Proactivity and adaptation based on corrective actions seem to imply exposure of much more

information across layers than is typical in systems today.

Layering cleanly separates abstraction from implementation and is thus consistent with sound software

engineering.

Layering is also conducive to standardization since it encourages the creation of modular software

components.

Problem Space

Privacy and trust

As a user becomes more dependent on a pervasive computing system, it becomes more knowledgeable

about that user’s movements, behavior patterns and habits.

Exploiting this information is critical to successful proactivity and self-tuning (invisibility), but also

may cause serious loss of privacy.

User must trust the infrastructure to a considerable extent and the infrastructure needs to be confident

of the user’s identity and authorization level before responding to his/her requests.

It is a difficult challenge to establish this mutual trust in a manner that is minimally intrusive and thus

preserves invisibility.

Example Projects

Pervasive computing projects have emerged at major universities and in industry:

Project Aura (Carnegie Mellon University)

Oxygen (Massachusetts Institute of Technology)

Portalano (University of Washington)

Endeavour (University of California at Berkeley)

Place Lab (Intel Research Laboratory at Seattle)

Example Projects : Project Aura (4)

The Airport Scenario

Jane wants to send e-mail from the airport before her flight leaves.

She has several large enclosures

She is using a wireless interface

She has many options.

Simply send the e-mail

Is there enough bandwidth?

Compress the data first

Will that help enough?

Pay extra to get reserved bandwidth

Are reservations available?

Send the “diff” relative to older file

Are the old versions around?

Walk to a gate with more bandwidth

Where is there enough bandwidth?

How do we choose automatically?

Example Projects : Project Aura (5)

The Mobile Task Scenario

Aura saves Scott’s task.

Scott enters office and gets strong authentication and secure access.

Aura restores Scott’s task on desktop machine and uses a large display.

Scott controls application by voice.

Bradley enters room.

Bradley gets weak authentication, Scott’s access changes to insecure.

Aura denies voice access to sensitive email application.

Scott has multi-modal control of PowerPoint application.

Aura logs Scott out when he leaves the room.

Example Projects : Oxygen

Oxygen (MIT)

Pervasive human-centered computing.

Goal of Oxygen is bringing abundant computation and communication, as pervasive and free as air,

naturally into people's lives.

Example Projects : Oxygen (2)

To support highly dynamic and varied human activities, the Oxygen system must be

pervasive— it must be everywhere, with every portal reaching into the same information base;

embedded— it must live in our world, sensing and affecting it;

nomadic— it must allow users and computations to move around freely, according to their needs;

adaptable— it must provide flexibility and spontaneity, in response to changes in user requirements

and operating conditions;

powerful, yet efficient— it must free itself from constraints imposed by bounded hardware resources,

addressing instead system constraints imposed by user demands and available power or

communication bandwidth;

intentional— it must enable people to name services and software objects by intent, for example, "the

nearest printer," as opposed to by address;

eternal— it must never shut down or reboot; components may come and go in response to demand,

errors, and upgrades, but Oxygen as a whole must be available all the time.

Related Projects: Portalano

Portolano (University of Washington)

An expedition into invisible computing.

Expedition goals:

Connecting the physical world to the world-wide information fabric

Instrument the environment: sensors, locators, actuators

Universal plug-and-play at all levels: devices to services

Optimize for power: computation partitioning, comm. opt.

Intermittent communication: new networking strategies

Get computers out of the way

Don’t interfere with user’s tasks

Diverse task-specific devices with optimized form-factors

Wide range of input/output modalities

Robust, trustworthy services

High-productivity software development

Self-organizing, active middleware, maintenance, monitoring

Higher-level, meaningful services

Related Projects: Portalano (2)

Scenario

Alice begins the day with a cup of coffee and her personalized newspaper.

When her carpool arrives, she switches to reading the news on her handheld display, where she notices

an advertisement for a new 3-D digital camera.

It looks like something that would interest her shutterbug-friend Bob, so Alice asks her address book

to place the call.

Related Projects: Portalano (3)

Scenario (2)

Bob's home entertainment system softens the volume of his custom music file as his phone rings.

Alice begins telling Bob about the camera, and forwards him a copy of the advertisement which pops

up on his home display.

Bob is sold on the product, and after hanging up with her, he asks his electronic shopping agent to

check his favorite photography stores for the lowest price and make the purchase.

Related Projects: Portalano (4)

Scenario (3)

When the camera arrives, Bob snaps some photos of his neighbor's collection of antique Portuguese

navigation instruments.

After reviewing the photo album generated automatically by a web-based service, Bob directs a copy

of his favorite image to the art display in his foyer.

He also sends a pointer to the photo album to Alice and instructs his scheduling agent to set up a lunch

date so that he can thank her for the suggestion.

Other Scenarios

Buy drinks by Friday (1)

Take out the last can of soda

Swipe the can’s UPC label, which adds soda to your shopping list

Make a note that you need soda for the guests you are having over this weekend

Other Scenarios

Buy drinks by Friday (2)

Approach a local supermarket

AutoPC informs you that you are near a supermarket

Opportunistic reminder: “If it is convenient, stop by to buy drinks.”

Other Scenarios

Buy drinks by Friday (3)

- Friday rolls around and you have not bought drinks

- Deadline-based reminder sent to your pager

Other Scenarios

Screen Fridge

Provides:

Email

Video messages

Web surfing

Food management

TV

Radio

Virtual keyboard

Digital cook book

Surveillance camera

Other Scenarios

The Active Badge

This harbinger of inch-scale computers contains a small microprocessor and an infrared transmitter.

The badge broadcasts the identity of its wearer and so can trigger automatic doors, automatic

telephone forwarding and computer displays customized to each person reading them.

The active badge and other networked tiny computers are called tabs.

Other Scenarios

The Active Badge

Other Scenarios

Edible computers: The pill-cam

Miniature camera

Diagnostic device

It is swallowed

Try this with an ENIAC computer!

Other Scenarios

Artificial Retina

Direct interface with nervous system

Whole new computational paradigm (who’s the computer?)

Other Scenarios

Smart Dust

Nano computers that couple:

Sensors

Computing

Communication

Grids of motes (“nano computers”)

PART II

Requirements of computational infrastructure:

failure management.

Security.

Performance.

dependability.

This is an architecture for pervasive computing applications that support multiple devices, such as PCs,

WAP phones, PDA and voice-only phones enabled to access Web servers through voice gate-ways.

The architecture addresses the special problems associated with pervasive computing, including diversity

of devices, markup language and authentication methods.

shows how pervasive computing applications based on this architecture can be secured.

Users have many different devices that look and behave in very different ways.

Examples of several kinds of pervasive computing devices includes WAP phones, PDAs, and voice-

recognition devices.

These devices proving different user interfaces, use different markup languages, use differer.-

communication protocols, and have different ways of authenticating themselves to servers.

Ideally, Web applications that support pervasive computing should adapt to whatever device their users

are using.

Applications must provide content in a form that is appropriate for the user's particular device - WML for

WAP phones, VoiceXML for voice interaction via a voice browser, HTML for PCs, and so on.

If device capabilities differ significantly, the entire interaction between the user and the Web application

has to be tailored : the device's capabilities to provide a good user experience.

A good example for this is access to a Web application from a PC versus access to the same Web

application from a WAP phone.

As the PC has a large screen, it is appropriate to present a substantial amount of information per screen

and it is possible to have many entry fields in a single form with extensive selections

A typical dialog between the PC user and the Web application consists of just a few screens.

When the user accesses the same applica-tion from a WAP phone, only a small amount of information

can be displayed on a single screen, and only a handful of entry fields may be contained in a form;

both input and output have to be reduced to an absolute minimum. Wherever possible, applications

should employ per-sonalization to avoid unnecessary data input or at least provide good suggestions,

A typical dialog between a WAP user and the Web application consists of more screens than the

equivalent dialog with a PC user; at the same time, the amount of data that has to be entered by the user

has to be minimized.

Architectures for pervasive computing applications must not only allow for filtering of unnecessary

information, and for output targeted to different devices, but must also be flexible enough to

accommodate different flows of interaction depending on the user's device.

Given the ever-growing number of pervasive computing devices, scalability of pervasive computing

applications is a very important issue.

Large telecommunication companies expect millions of users to subscribe for some applications, for

example.

Availability is of particular importance in the pervasive computing environment.

Unlike PC users, most users of pervasive computing devices and applications will neither understand nor

accept comments like 'server currently down for maintenance' - if a service is not available when they

need it, they will assume that it does not work, and will stop using the application or switch to another

service provider.

Both issues can be resolved by system topologies that employ parallelism and redundancy to guarantee

scalability and availability. An example of such a topology is shown in Figure.

Scalability and availability can be achieved by running multiple instances of every component that might

become a bottleneck.

Typically the gateways perform tasks that require significant computing power.

WAP gateways, for example, may have to execute the WTLS protocol in the direction of the clients, and

the SSL protocol in the direction of the servers.

for many parallel sessions, requiring computation-intensive decryption and encryption of data. Voice

gateways use voice recognition engines and thus require even more computing power.

A scalable system will use a cluster of gateways for each device type, to which additions, machines can

be added as required.

From the various gateways, a potentially large number of requests flow to the servers that host pervasive

computing Web applications.

Typically the network dispatcher is used to route incoming requests to the appropriate servers, balancing

the load between them.

To support efficient handling of HTTPS, the dispatchers support a mode in which requests originate from

a particular client are always sent to the same server to avoid repeating SSL handshakes.

To assure high availability, pairs of network dispatchers can be used, in which one is active and a back-

up monitors heartbeat of the active dispatcher to take over if a failure occurs.

To allow for central authentication, authorization, and enforcement of access policies, authentication

proxies are used, located in the demilita-rized zone between two firewalls, so that all incoming requests

can flow to application servers only via the authentication proxies.

They check each incoming request to see whether the client from which it originates is already known,

and whether it is allowed to access the desired target function of the Web application according to a

centrally defined policy.

To do so, it needs access to the credentials required for authentication and to the policies for

authorization.

If a request from a new client arrives, the authentication proxy performs client authentication before

letting any request pass through to the application servers.

An authentication proxy may consume significant computing power, e.g. when SSL server authentication

has to be performed for a large number of sessions.

Thus, a cluster of authentication proxies is required for larger systems.

Requests initiated by authenticated clients flow from the authentication proxies to the application servers

behind the inner firewall.

The application code and the presentation functions that make up the Web application front end is

running on these servers.

Here, the requests coming from the clients are received and processed.

To implement a scalable Web application, a cluster of application servers is usually used to which

additional machines can be added when the load increases.

Typically, the front end of a Web application interacts with a back end that hosts persistent data and/or

legacy systems.

Development of pervasive computing Web applications

To implement Web applications, four major kinds of role are typically required in a development team:

business logic designers, user interface designers, application programmers, and experts for existing

legacy data-base and transaction systems.

Business logic designers define the functions to be performed and the application flow.

User interface designers are responsible for application design, defining the look and feel of the Web

application, designing user interaction, and guaranteeing good usability.

Web designers work with technologies such as HTML and JSPs, mostly using high-level visual tools.

Application developers are responsible for implementing the application logic and connectivity to

database and transaction systems in the back end.

Java developers work with technologies such as servlets, EJBs, LDAP, JDBC, etc.

In teams developing pervasive computing applications, an additional role is usually needed - the

pervasive computing specialist, who knows about the capabilities of devices and the infrastructure

required to support pervasive computing applications, such as WAP gateways, voice gateways and

gateways for PDAs.

These people are the experts in tech-nologies such as WML and VoiceXML, which normally cannot be

handled well by traditional Web designers.

Pervasive application architecture

The model-view-controller (MVC) pattern is a good choice when implementing Web applications.

standard mapping of the pattern to servlets, JSPs, and EJBs, where controller is implemented as a

servlet, the model implemented as a secure EJBs, and the views as JSPs.

Pervasive computing applications, however, add an additional level of complexity.

As devices are very different from each other, we can assume that one controller will fit all device

classes. In the MVC pattern the controller encapsulates the dialog flow of an application.

This flow will be different for different classes of devices, such as WAP phone, voice-only phones, PCs,

or PDAs.

Thus, we need different controller for different classes of devices.

To support multiple controllers, we replace the servlet's role to that of a simple dispatcher that invokes

the appropriate controller depending on the type of device being used

MVC Pattern applied to Pervasive Computing Applications

Securing pervasive computing applications

Like traditional Web applications, Web applications supporting pervasive devices have to be secured by

appropriate encryption, authentication, using authorization mechanisms.

The secure pervasive access architecture presented here is designed to process client requests on the

application server in a secure and efficient way.

It addresses user identification, authentication, and authorization of invocation of application depending

on configurable security policies.

Figure shows an example in which the a user accesses a function of a particular Web application from a

WAP phone.

Secure Pervasive Access Architecture

All incoming requests originate from the device connectivity infrastructure.

This infrastructure may include different kinds of gateways that convert device-specific requests to a

canonical form, i.e. HTTP request that may carry information about the device type, the desired language

and the desired reply content type, e.g. HTML,WML,or VoiceXML.

Examples of gateways in the device connectivity layer are voice gateways with remote VoiceXML-

browsers, WAP gateways, and gateways for con-necting PDAs.

An important function that the device connectivity layer must provide is support of session cookies to

allow the application server to associate a session with the device.

The secure access component is the only system component allowed to invoke application functions.

It checks all incoming requests and calls application functions according to security policies stored in a

database or directory.

A particular security state - part of the session state - is reached by authentication of the client using

user-ID and password, public-key client authentication, or authentication with a smart card, for example.

If the requirements for permissions defined in the security policy are met by the current security state of a

request's session, then the secure access layer invokes the requested application function, e.g. a function

that accesses a database and returns a bean.

Otherwise, the secure access component can redirect the user to the appropriate authentication page.

Typically, the secure access component will be implemented as an authentication proxy within a

demilitarized zone as shown earlier.

Finally, the output generated by the application logic is delivered back to the user in a form appropriate

for the device he or she is using. In the

In the Figure , the information to be displayed is prepared by the application logic and passed to the

content-delivery module encapsulated in beans.

The content-delivery module then extracts the relevant part of the information from the bean and renders

it into content that depends on the device type and desired reply content type, for example by calling

appropriate JSPs.

The content-delivery module delivers the content generated in the previous step via the device

connectivity infrastructure that converts canonical responses (HTTP responses) to device-specific

responses, using-appropriate gateways.

For example, if a user accesses the system via a telephone, the voice gateway receives the HTTP

response with VoiceXML content and leads an appropriate 'conversation' with the user, finally resulting

in a new request being sent to the server.

Context Awareness

Context Awareness - State + Surroundings

Context

Who – identity

What – Perceiving the activity

Where - Location – Physical environment, Computational environment

When - Time

Why - Behavior - linked to emotions

Time

Current context – snapshot, Historical context – context across time

Application - Proactive approach

Here is what you did last time

Here is what your friend did last time

Here is what an expert did last time

Key Research issues

Finding context

Representing context

UNIT I

PART II

Pervasive Architecture

Architecture is an abstraction of the system.

Architecture defines the system elements and how they interact.

Architecture suppresses the local information about the elements.

Defines the properties of the components

Provided services, required services, performance characteristics, fault handling, resource usage

Pervasive Architecture

Software components for pervasive computing

Device heterogeneity

Access control

Software Components

The pervasive computing environment forces us to face the need for components and their boundaries

more clearly.

Pervasive services will have to be composed from individual “components” residing in the large number

of heterogeneous computing elements.

The hardware environment itself will force a natural boundary between components. This may be the

most clear-cut definition of a component.

A component will be an independently deployable piece of software that resides on one hardware

element and provides a service element. Of course, there may be more than one component on each

hardware element.

Example – WEB SERVICES

Security

What data do I wish to expose? To whom?

Who can presently access my data?

How can I retract data exposed?

Who am I communicating with?

How do can the privacy of my communication and communication patterns?

Who do I trust as a source of information?

How do I convince others that I am trustworthy?

How to make systems simultaneously secure and usable?

• Establish strong identity

Goal: Cryptographically strong identity to devices (endpoints)

Means: Host Identity Protocol (HIP)

– Identify each communicating device with a cryptographic public key

– Insert the key into the TCP/IP stack

– Assign and manage trust and authority

Goal: Decentralised means for managing authorisation

Means: SPKI and KeyNote2 certificates

Express delegation with signed statements

Eventually integrate to the operating system

– Enable build-up of trust and reputation based on experiences

Goal: Creation of trustworthy behaviour

Means: Micro economic mechanism design

Design the rules for the game

Make unsocial behaviour uneconomical

Device Heterogeneity

The basic premise of pervasive computing—everything connected—guarantees heterogeneity at all

levels: infrastructure, hardware, software, and people.

All kinds of devices must be supported. Perhaps in some specific application scenarios it is possible to

restrict the kinds of devices that are supported but, in general, the environment must anticipate the

existence of a wide variety of devices.

If we consider devices used by the user to interact with the system, they can range from standard ones

such as laptops, PDAs, and phones, to emerging ones such as those embedded in clothing and eyeglasses.

The variety of available devices has several implications. One is the kind of input-output devices: textual

and graphic input-output will not be the only forms of human-machine interaction.

Audio, visual, and other sensory modes of communication will be prevalent. Another implication is the

requirement that the environment must be prepared to adapt to the device currently used by the user.

For example, if the user is requesting information and he is currently driving, the retrieved data should

be relayed to him with an audio message through the car radio.

Access Control

The wide availability of services and the high mobility of users among different environments require the

provision of security mechanisms to ensure the safe usage of services by legitimate users and the

protection of services from unauthorized uses.

Because of the wide range of services, many diverse and flexible security models and mechanisms will

be needed. Either standard security mechanisms will have to be embedded in the environment and used

by all applications or each application will have to build its own security mechanisms. Most likely, a

combination of the two will be needed.

One of the most important aspects of security is access control, to ensure that services are only available

to authorized users and those authorized users are allowed appropriate privileges .

For example, a guest at a hotel may be allowed to print on the hotel’s printer available in the lobby but

not change the contents of the event display in the same lobby.

Single-sign on policy

Securing Pervasive Networks Using Biometrics

Challenges in pervasive computing environments

Computing devices are numerous and ubiquitous

Traditional authentication including login schemes do not work well with so many devices

Proposed Solution

Use biometrics for authentication

At the same time, ensure security of biometric templates in an open environment

Contributions

Propose a biometrics based framework for securing pervasive environment

Implemented a novel scheme for securing biometric data in an open environment using symmetric

hash functions

Aspects of a Pervasive Environment

User Interaction

User interacts with speech, gestures and movements

The sensors and computing devices are ‘aware’ of the user and in the ideal case are also aware of his

‘intent’.

Proactivity

The computing devices should interact and query other devices on Transparency

Technology has to be transparent.

behalf of the user and his intent

Device interaction

Frequent Multiparty interactions

No central authority or third party

Security and Privacy

Consequences of a pervasive network

Devices are numerous, ubiquitous and shared

The network shares the context and preferences of the user

Smart spaces are aware of the location and intent of the user

Security Concerns

Only authorized individuals need to be given access

Authentication should be minimally intrusive

Devices should be trustworthy

Privacy issues

User should be aware of when he is being observed

The user context should be protected within the network

Need to balance accessibility and security

Should be scalable with multiple users operating in the network

Solution: Biometrics?

Definition

Biometrics is the science of verifying and establishing the identity of an individual through

physiological features or behavioral traits.

Examples

Physical Biometrics

Fingerprint

Hand Geometry

Iris patterns

Behavioral Biometrics

Handwriting

Signature

Speech

Gait

Chemical/Biological Biometrics

Perspiration

Skin composition(spectroscopy)

Why Biometrics?

Advantages of biometrics

Uniqueness

No need to remember passwords or carry tokens

Biometrics cannot be lost, stolen or forgotten

More secure than a long password

Solves repudiation problem

Not susceptible to traditional dictionary attacks

General Biometric System

Framework for Authentication/Interaction

Framework for Authentication/Interaction

Framework for Authentication/Interaction

Framework for Authentication/Interaction

Framework for Authentication/Interaction

Speaker Recognition

Framework is Generic

Security of Biometric Data

Issues in biometrics

Biometrics is secure but not secret

Permanently associated with user

Used across multiple applications

Can be covertly captured

Types of circumvention

Denial of service attacks(1)

Fake biometrics attack(2)

Replay and Spoof attacks(3,5)

Trojan horse attacks(4,6,7)

Back end attacks(8)

Collusion

Coercion

Hashing

Hashing

Instead of storing the original password P, a hashed values P’=H(P) is stored instead.

The user is authenticated if H(password) = P’.

It is computationally hard to recover P given H(P)

H() – one way hashing function

Problem with biometrics

Biometric data has high uncertainty

Matching is inexact/probabilistic

Therefore, hashing function should be error tolerant

Biometric Hashing

Fingerprints

Conclusion

Smart spaces and pervasive computing are moving from concepts to implementations

Security has to be incorporated in the design stage

Traditional authentication and access control paradigms cannot scale to numerous and ubiquitous devices

Biometrics serves as a reliable alternative for minimally intrusive authentication

Biometrics solves key management and repudiation problem

Securing biometrics is a major challenge in an open environment

Biometric hashing can be used to create revocable biometric templates

Biometrics

• Access to systems providing significant monetary value, confidential information, or critical applications

must be secured against unautho-rized use.

• User authentication is therefore a key function in any such system. Classical authentication relies on

what you own, what you are, and what you know.

• Typically, Internet applications rely on user identifier (UID) and a password.

• The UID may be in the public knowledge, whereas the pass-word is a secret (what you know) shared by

the user and the system administration.

• Thus, the system can check whether the user is author-ized to use the system.

• However, any person who knows the password can perform user functions.

• The password can be stolen by watching the user enter their personal identification number (PIN), by

capturing data during password transmission, or via access to system administration data.

• A stolen password is hard to detect because nothing is removed from any system.

• GSM mobile phones are protected against unauthorized use through the SIM, a smart card that is issued

by the mobile service provider (what you have) and a PIN chosen by the customer (what you know).

• The PIN is stored and checked in the secure system environment of the SIM and is not transmitted via

unreliable media.

• Intruders must steal the SIM and the PIN in order to act like the authorized user and perform user

func-tions.

• However, many users prefer not to use a PIN because it is inconvenient, and complicated procedures are

required to recover a for gotten PIN and assign a new one

• Biometrics authentication methods rely on what you are.

• A large number of personal characteristics, such as fingerprint, signature, ham geometry, face

recognition, voice recognition, and iris scan, have been proposed.

• Only methods that work with small sensors, e.g. microphone fingerprint sensor, or pen entry panels,

promise near-term applicability of the pervasive computing space.

• Therefore, only authentication using fingerprint, speaker verification, or signature verification is

discussed in the following section.

• Biometrics authentication systems capture the user's characteristic with a sensor, derive characteristic

values, and compare this with known reference.

• The result of the comparison is either 0, if authentication was not successfully performed, or 1, if

authentication was successful.

• In fingerprint verification, the image system extracts the end and the bifurcation points of finger lines,

and uses location and direction as characteristic values for comparison with one or more stored references

.

• Generation of reference values and actual values is subject to distortion.

• The comparison of the data sets is rather complete and introduces additional errors.

• Therefore, there is always the probability that biometrics authentication will fail, causing major

inconvenience to the user.

• The false accept rate (FAR) is the probability that the system will accept the wrong user. The false reject

rate (FRR) is the probability; that the system will reject the correct user.

PART II

Pervasive web Application Architecture

Requirements of computational infrastructure:

• failure management.

• Security.

• Performance.

• dependability.

• This is an architecture for pervasive computing applications that support multiple devices, such as PCs,

WAP phones, PDA and voice-only phones enabled to access Web servers through voice gate-ways.

• The architecture addresses the special problems associated with pervasive computing, including diversity

of devices, markup language and authentication methods.

• shows how pervasive computing applications based on this architecture can be secured.

• Users have many different devices that look and behave in very different ways.

• Examples of several kinds of pervasive computing devices includes WAP phones, PDAs, and voice-

recognition devices.

• These devices proving different user interfaces, use different markup languages, use differrent

communication protocols, and have different ways of authenticating themselves to servers.

• Ideally, Web applications that support pervasive computing should adapt to whatever device their users

are using.

• Applications must provide content in a form that is appropriate for the user's particular device - WML for

WAP phones, Voice XML for voice interaction via a voice browser, HTML for PCs, and so on.

• If device capabilities differ significantly, the entire interaction between the user and the Web application

has to be tailored : the device's capabilities to provide a good user experience.

• A good example for this is access to a Web application from a PC versus access to the same Web

application from a WAP phone.

• As the PC has a large screen, it is appropriate to present a substantial amount of information per screen

and it is possible to have many entry fields in a single form with extensive selections

• Architectures for pervasive computing applications must not only allow for filtering of unnecessary

information, and for output targeted to different devices, but must also be flexible enough to

accommodate different flows of interaction depending on the user's device.

Scalability and availability

• Given the ever-growing number of pervasive computing devices, scalability of pervasive computing

applications is a very important issue.

• Large telecommunication companies expect millions of users to subscribe for some applications, for

example.

• Availability is of particular importance in the pervasive computing environment.

• Unlike PC users, most users of pervasive computing devices and applications will neither understand nor

accept comments like 'server currently down for maintenance' - if a service is not available when they

need it, they will assume that it does not work, and will stop using the application or switch to another

service provider.

• Both issues can be resolved by system topologies that employ parallelism and redundancy to guarantee

scalability and availability. An example of such a topology is shown in Figure.

• Scalability and availability can be achieved by running multiple instances of every component that might

become a bottleneck.

• Typically the gateways perform tasks that require significant computing power.

• WAP gateways, for example, may have to execute the WTLS protocol in the direction of the clients, and

the SSL protocol in the direction of the servers for many parallel sessions, requiring computation-

intensive decryption and encryption of data.

• Voice gateways use voice recognition engines and thus require even more computing power.

• A scalable system will use a cluster of gateways for each device type, to which additions, machines can

be added as required.

• From the various gateways, a potentially large number of requests flow to the servers that host pervasive

computing Web applications.

• Typically the network dispatcher is used to route incoming requests to the appropriate servers, balancing

the load between them.

• To support efficient handling of HTTPS, the dispatchers support a mode in which requests originate from

a particular client are always sent to the same server to avoid repeating SSL handshakes.

• To assure high availability, pairs of network dispatchers can be used, in which one is active and a back-

up monitors heartbeat of the active dispatcher to take over if a failure occurs.

• To allow for central authentication, authorization, and enforcement of access policies, authentication

proxies are used, located in the demilita-rized zone between two firewalls, so that all incoming requests

can flow to application servers only via the authentication proxies.

• They check each incoming request to see whether the client from which it originates is already known,

and whether it is allowed to access the desired target function of the Web application according to a

centrally defined policy.

• To do so, it needs access to the credentials required for authentication and to the policies for

authorization.

• If a request from a new client arrives, the authentication proxy performs client authentication before

letting any request pass through to the application servers.

• An authentication proxy may consume significant computing power, e.g. when SSL server authentication

has to be performed for a large number of sessions.

• Thus, a cluster of authentication proxies is required for larger systems.

• Requests initiated by authenticated clients flow from the authentication proxies to the application servers

behind the inner firewall.

• The application code and the presentation functions that make up the Web application front end is

running on these servers.

• Here, the requests coming from the clients are received and processed.

• To implement a scalable Web application, a cluster of application servers is usually used to which

additional machines can be added when the load increases.

• Typically, the front end of a Web application interacts with a back end that hosts persistent data and/or

legacy systems.

Development of pervasive computing Web applications

• To implement Web applications, four major kinds of role are typically required in a development team:

business logic designers, user interface designers, application programmers, and experts for existing

legacy data-base and transaction systems.

• Business logic designers define the functions to be performed and the application flow.

• User interface designers are responsible for application design, defining the look and feel of the Web

application, designing user interaction, and guaranteeing good usability.

• Web designers work with technologies such as HTML and JSPs, mostly using high-level visual tools.

• Application developers are responsible for implementing the application logic and connectivity to

database and transaction systems in the back end.

• Java developers work with technologies such as servlets, EJBs, LDAP, JDBC, etc.

• In teams developing pervasive computing applications, an additional role is usually needed - the

pervasive computing specialist, who knows about the capabilities of devices and the infrastructure

required to support pervasive computing applications, such as WAP gateways, voice gateways and

gateways for PDAs.

• These people are the experts in tech-nologies such as WML and VoiceXML, which normally cannot be

handled well by traditional Web designers.

Pervasive application architecture

• The model-view-controller (MVC) pattern is a good choice when implementing Web applications.

• standard mapping of the pattern to servlets, JSPs, and EJBs, where controller is implemented as a

servlet, the model implemented as a secure EJBs, and the views as JSPs.

• Pervasive computing applications, however, add an additional level of complexity.

• As devices are very different from each other, we can assume that one controller will fit all device

classes. In the MVC pattern the controller encapsulates the dialog flow of an application.

• This flow will be different for different classes of devices, such as WAP phone, voice-only phones, PCs,

or PDAs.

• Thus, we need different controller for different classes of devices.

• To support multiple controllers, we replace the servlet's role to that of a simple dispatcher that invokes

the appropriate controller depending on the type of device being used

MVC Pattern applied to Pervasive Computing Applications

Securing pervasive computing applications

• Like traditional Web applications, Web applications supporting pervasive devices have to be secured by

appropriate encryption, authentication, using authorization mechanisms.

• The secure pervasive access architecture presented here is designed to process client requests on the

application server in a secure and efficient way.

• It addresses user identification, authentication, and authorization of invocation of application depending

on configurable security policies.

• Figure shows an example in which the a user accesses a function of a particular Web application from a

WAP phone.

Secure Pervasive Access Architecture

• All incoming requests originate from the device connectivity infrastructure.

• This infrastructure may include different kinds of gateways that convert device-specific requests to a

canonical form, i.e. HTTP request that may carry information about the device type, the desired language

and the desired reply content type, e.g. HTML,WML,or VoiceXML.

• Examples of gateways in the device connectivity layer are voice gateways with remote VoiceXML-

browsers, WAP gateways, and gateways for con-necting PDAs.

• An important function that the device connectivity layer must provide is support of session cookies to

allow the application server to associate a session with the device.

• The secure access component is the only system component allowed to invoke application functions.

• It checks all incoming requests and calls application functions according to security policies stored in a

database or directory.

• A particular security state - part of the session state - is reached by authentication of the client using

user-ID and password, public-key client authentication, or authentication with a smart card, for example.

• If the requirements for permissions defined in the security policy are met by the current security state of a

request's session, then the secure access layer invokes the requested application function, e.g. a function

that accesses a database and returns a bean.

• Otherwise, the secure access component can redirect the user to the appropriate authentication page.

• Typically, the secure access component will be implemented as an authentication proxy within a

demilitarized zone as shown earlier.

• Finally, the output generated by the application logic is delivered back to the user in a form appropriate

for the device he or she is using. In the