Mobile Agent Roll 01 & 02

8/3/2019 Mobile Agent Roll 01 & 02

http://slidepdf.com/reader/full/mobile-agent-roll-01-02 1/40

Anjan Mondal (Roll No. - 01)

Arnab Pal (Roll No. - 02)

M.E. (Software Engineering)

Dept. of Information Technology Jadavpur University

Sunday, April 22, 2012



Meaning of Agent ‘An agent is a computer system that is situated in some

environment, and that is capable of autonomous action

in this environment in order to meet its design objectives’.

Two basic properties of Software Agents :

Autonomicity – ability to act without direct human

intervention.

Situatedness – Agents tend to be used where the

environment is challenging (dynamic, unpredictable

and unreliable).




How Agent works

SENSORS

ACTUATORS




Other properties of Agent Reactive – senses changes in the environment and

acts accordingly to those changes.

Proactive – persistently pursues goals.

Flexible – has multiple ways of achieving goals.

Robust – recovers from failure.




Properties of Agent contd. Communicative – able to communicate withother agents.

Mobile – can travel from one host to another.

Learning – adapts in accordance with previous

experience.

Believable – appears believable to the end-user.




Definition of a Stationary Agent A stationary agent executes only on the system

where it begins execution. If it needs information

that is not on that system, or needs to interact withan agent on a different system, it typically uses acommunication mechanism such as remoteprocedure calling (RPC).




What is a Mobile Agent? Program that can migrate from system to system

within a network environment

Performs some processing at each host Agent decides when and where to move next

How does it move ?

Save stateTransport saved state to next system

Resume execution of saved state




Evolution End point in the incremental evolution of mobile

abstractions such as mobile code, mobile objects,mobile processes.

Mobile Code – transfers (code)

Mobile Object – transfers (code + data)

Mobile Process – transfers

(code + data + thread state) Mobile Agent – transfers

(code + data + thread + authority of its owner)




A Mobile Agent Dissected A mobile agent contains the following 3 components:

Code - the program (in a suitable language) that definesthe agent's behavior.

State - the agent's internal variables etc., which enable itto resume its activities after moving to another host.

Attributes - information describing the agent, its originand owner, its movement history, resource requirements,authentication keys etc. Part of this may be accessible tothe agent itself, but the agent must not be able to modify the attributes




Levels of Mobility Weak Mobility

When moving a mobile agent carries

(code + data state)

Data State - global or instance variable

On moving, execution has to start from thebeginning




Levels of Mobility Strong Mobility

When moving a mobile agent carries

(code + data state + execution state) Data State - global or instance variable

Execution State – local variables and threads

On moving, execution can continue from thepoint it stopped on the previous host




Events in Mobile Agent’s life-time Creation: a brand new agent is born and its state is

initialized.

Dispatch: an agent travels to a new host.

Cloning: a twin agent is born and the current state of the original is duplicated in the clone.

Deactivation: an agent is put to sleep and its state is

saved in persistent storage.

Activation: a deactivated agent is brought back to lifeand its state is restored from persistent storage.




Events in Mobile Agent’s life-time

Retraction: an agent is brought back from a remotehost along with its state to the home machine.

Disposal: an agent is terminated and its state is lostforever.

Communication: Notifies the agent to handle

messages incoming from other agents , which is theprimary means of inter-agent correspondence.




Agent Life-Cycle Model

Agent Agent

ClassFileDisk

Storage

CreateDeactivate Activate

Dispose

Clone

Retract

Dispatch

Context BContext A

Agent Life Cycle

Agent

Disk

Storage

Disk

Storage

-Creation

-Cloning

-Dispatching andRetraction (Mobility )

-Disposal

-Activation andDeactivation (Persistence)




Applets, Servlets and Mobile Agents Applet – Downloaded from server to client.

Servlet – Uploaded from client to server.

Mobile Agents – Detached from client, can have

multiple hops.




Mobile Code Systems: Design Four basic types:

Client/Server

Code on DemandRemote Evaluation

Mobile Agents

Elements

Data (stored result sets)Code (commands)

Program stack (current status of the program)




Client/Server




Client/Server Discussion Examples: WWW, RPC, Webservices, CORBA, EJBs Elements

data - mobilecode - staticprogram stack – static

Advantageseasy to implement

widespread Disadvantagesthere‘s no “one size fits all“

CORBA (Common Object Request Broker Architecture), EJB (Enterprise JavaBeans)




Mobile Agents

ResultSunday, April 22, 2012



Mobile Agents Discussion Elements

data - semi-mobile (necessary data is mobile)code - mobile

program stack – mobile

The Mobile Agent paradigm can solve all distributed computing issues

NO! Mobile Agents are not a substitute for client-server techniques. The two techniques augment eachother and very often a combination of the two is themost appropriate.




Seven Good Reasons for Mobile Agents Danny Lange’s Seven Good Reasons For Mobile Agents

They reduce network load

They overcome network latency

They encapsulate protocols

They execute asynchronously and autonomously

They adapt dynamically

They are naturally heterogeneousThey are robust and fault-tolerant

There is still no killer app for mobile agents!




Companies and Products IBM: AgletsInformation on Aglets can be found at http://www.trl.ibm.co.jp/aglets

FTP Software: CyberAgentsInformation on CyberAgents used to be able to be found at http://www.ftp.com/cyberagents

General Magic: TabrizMore information on Tabriz can be found at http://www.genmagic.com/tabriz

Languages:The following languages are being used today for authoring agents.

Java, Telescript, TCL or Tools Control Language, Obliq, Python







Security Threats Threats to security generally fall into three main classes:

Disclosure of information

Denial of service

Corruption of information




Agent System Model

HOMEplatform Agent platform Agent

Agent platform

Network




Malicious agents

Malicious agencies.




Malicious AgentsMalicious agents are those that try to attack thehosting agency or other agent.

Classification malicious agents according to thetarget they attack

Attacking the Hosting Agency. Attacking Other Agents




Attacking the Hosting Agency 1. The most obvious example of a malicious agent is

one that consumes resources of the hostingenvironment in an improper way.

Recourses may be :

Memory,

CPU cycles, Network bandwidth

Effect : The agency eventually is not able to provide its usualservice to other agents.




Attacking the Hosting Agency(2)

2. The second type of attack to the hosting agency is when an agent tries to gain unauthorized access tothe agency.

private keys of the agency or its users.

An agent could also try to disclose the agency’s code oreven try to terminate the agency completely




Attacking Other Agents No agent must have access to any other agent on the

programming language level.

If we assume object-oriented programming languages,no agent should ever obtain a direct reference of another agent. Otherwise, the malicious agent would

gain full control of the referenced agent.




Attacking Other Agents(2) A malicious agent could initiate denial of service attacks

on other agents, for example, by sending thousands of spam messages.




Malicious Agencies A malicious agency is one that tries to attack mobile

agents currently residing on it or other agencies by attacking the communication link.

Two types of attack can occur-

• Passive attack.

•

Active attack.




Passive attackTraffic analysis

each message is encrypted because it is not important whether the data is readable(understandable) to theattacker. Here, the adversary attempts to find patternsin the communication between two agencies, which

might allow the adversary to derive certainassumptions based on these patterns.




Attacker

Passive attack Traffic analysis

A B

c




Active Attack Active attacks include security threats in which an

agency tries to manipulate agent code or data while itis transmitted between agencies. The most common

examples of this kind of attack are alterations, inwhich an agent’s data is deleted or tampered with by an agency




Active attack

Malicious Agencies

A B

Agency A Agency B




Example

Platform 4

Malicious host Platform 3Platform 2 Agent

Migration




Attacking Agents cut and paste attack

This attack works even if data has been encrypted so thatIt can be read only at specific agencies. An agent, α, carries a data item protected with the public key of an

agency, Ai that the agent is going to visit.

a malicious agency, Am, which currently is hosting agent α, could cut

the data item, paste it into a new agent, and let this agent migrate to Ai. The new agent decrypts the data item and carries it back to agency Am.




References: Mobile Agents Basic Concepts, Mobility Models, and the Tracy Toolkit

Peter Braun Swinburne University of Technology, Victoria, Australia

Wilhelm Rossak ,Friedrich Schiller University, Jena, Thuringia,Germany.

Mobile agent security Niklas Borselius Mobile VCE Research GroupInformation Security Group, Royal Holloway, University of London

Artificial Intelligence A Modern Approach by Russell & Norvig, Second

Edition, Prentice Hall.




Thank You

Documents

Mobile Agent Roll 01 & 02