LYU9905 Security in Mobile Agent E-Commerce Systems

LYU9905LYU9905Security in Mobile Agent E-Commerce SystemsSecurity in Mobile Agent E-Commerce Systems

Prepared by : Wong Ka Ming, Caris

Wong Tsz Yeung, Ah Mole

Supervisor : LYU Rung Tsong Michael

Date : 7/12/99

LYU9905 Security in Mobile Agent E-Commerce Systems

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OutlineOutline

• Introduction

• What is Mobile Agent

• Overview of SIAS - Shopping Information Agent System

• Security in Mobile Agent System & Cryptography

• Security Attacks and Defenses Scenarios in SIAS

• Future Work

• Q & A Session


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Introduction (1)Introduction (1)

• Mobile software agents has become an important aspect in the electronic commerce

• Electronic commerce and information retrieval are two prospective directions for application of mobile agents

• Security is a crucial concern for such system


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Introduction (2)Introduction (2)

• Discuss mobile agents properties and capability

• Describe the system we have build for the FYP – Shopping Information Agent System (SIAS)

• Discuss the security problems for the mobile agents

• Particularly, analyze possible security attacks by malicious hosts against agents in SIAS

• Last but not least, our solutions to detect these attacks


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What is Mobile Agent (1)What is Mobile Agent (1)

• Agent Definition - (User Perspective)

• An Agent is a program that assists people and acts on their behalf. Agents function by allowing people to delegate work to them

• Example : Stock Broker


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• Agent Definition - (System Perspective)

• An agent is a software object that is

• situated within an execution environment

• able to communicate with other agents

• mobile and able to travel from one host to another

• Autonomous, has control over its own actions


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• Dispatch, Disconnect, and Dispatch model


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• Advantages of mobile agent over Client/Server Paradigms

• Reduce the network load

• Overcome network latency

• Execute asynchronously and autonomously

• Adapt to changes dynamically

• Robust and fault-tolerant


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Mobile Agent ProductsMobile Agent Products

•Aglets from IBM

•Concordia from Mitsubishi

•Voyager from ObjectSpace


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Introducing SIAS (1)Introducing SIAS (1)

• SIAS - Shopping Information Agent System

• SIAS is a web-based e-commerce mobile agent system

• It provides users with information of products for sale in an electronic marketplace

• It is written in Java programming language and on top of the Concordia API, which is developed by Mitsubishi Electric Research Lab


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• An electronic market consists of hosts that sell products on the network

• Each seller maintains a database that stores the prices and quantities in stock of different products available at that host

• It allows users to specify a set of products and quantities


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• An agent is created for an user whenever he/she has specified a list of products and quantities

• After the agent has visited all hosts specified in its itinerary, it returns to its sender and reports the lowest prices and corresponding sellers

• The agent starts travelling in the network according to its itinerary (path), which is pre-determined while it is created


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• Simplified model for SIAS


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SIAS Details - Implementation (1)SIAS Details - Implementation (1)

• Four main objects in the system

• Agent - retrieves product information from hosts for users

• Launch Server -

• it is a gateway between agent system and client programs.

• It initializes and launches an agent whenever it receives requests from clients.

• It is also used for receiving agents when an agents finishes its trips


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• Database Server -

• Client Program -

• it is used for retrieving information from its own database.

• It also receives incoming agents and provides execution environments for them until they finish executions and leave

• It is a Java Applet which lets users to choose products and quantities.

• Each instance of the client program can communicate with the Launch Server


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• Our current SIAS design :

• One Launch Server - it is a trusted host.

• Three Data Base Servers - some of them may be malicious

• Client is using Netscape Communicator 4.5


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Data BaseServer 1

LaunchServer

Client request Report results to client

Data BaseServer 2

Data BaseServer 3

A new agent is createdThe agent is launched and starts to travelAgent is going to Data Base Server 1Agent arrives at Data Base Server 1Agent retrieves data from database and leavesAgent is going to Data Base Server 2Agent arrives at Data Base Server 2Agent retrieves data from database and leavesAgent is going Data Base Server 3Agent arrives at Data Base Server 3Agent retrieves data from database and leavesAgent is going back to Launch Server

Agent calculates the cheapest purchasing combination and it will be destroyed by the Launch Server


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• Technology used in Agent object

• Agent - it is a Concordia object

• It enables an object which is a subclass of Concordia Agent to dispatch (marshalling) itself into the network and retract (unmarshalling) into another host


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• Data Base Server - the Data Base Server uses an object namely Agent Transporter to receive and send agents.

• Agent Transporter is able to control every execution of a received agent.

• The database server used is Oracle 8i. Oracle provides a driver for JDBC, which is a Java Solution for Database Connectivity

• Technology used in Data Base Server object


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• Technology used in Launch Server object

• It also uses Agent Transporter to receive and send agents

• It uses RMI (Remote Method Invocation) to connect with clients

• Why RMI but not Agent??

• Concordia Problem - client needs to install the Concordia API in order to send and receive agents by web browser

• Not convenient to use, so choose RMI.


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• Technology used in client program

• It is a Java Applet

• It uses RMI to connect to Launch Server

• Can I have a look on it ?? Yes, you can


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Security in Mobile Agent (1)Security in Mobile Agent (1)

• Security problems of malicious agents against hosts

• Trojan horse attacks by malicious agents

• This can be effectively solved by

• strong authentication of the code sources

• verification of code integrity

• limiting the access rights of incoming agents to local resources of hosts


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• Security problems of malicious agents against hosts

• When an agent executes on a remote host, the host is likely to have access to all the data and code carried by the agent

• If a host is malicious and abuses the code or data, the privacy and secrecy of the agent and its owner would be at risk


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• Seven types of attacks by malicious hosts

• Spying out and manipulation of code

• Spying out and manipulation of data

• Spying out and manipulation of control flow

• Incorrect execution of code

• Masquerading of the host

• Spying out and manipulation of interaction with other agents

• Returning wrong results of system calls to agents


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• In SIAS, we have chosen a technique called Agent Tempering Detection

• Agent Tempering Detection: hiding from hosts the data possessed by agents and the function to be computed by agents by messing up code and data of agents, or using cryptographic technique

• We will discuss: Asymmetric Cryptography & Digital Signature


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Asymmetric Cryptography (1)Asymmetric Cryptography (1)

• The main difference between asymmetric & traditional cryptography is the introduction of public key and private key

• Public key & private key are generated in pairs

• The message is then encrypted, transmitted and decrypted at the other end, without the need to pass around the private key, which put the private key under risks of exposure to the public


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Asymmetric Cryptography (2)Asymmetric Cryptography (2)

• Digital Signature is used to verify the entity that has been signed

• A person who send a message can append an encrypted form of the message, using sender’s private key, to the end of the message.

• The receiver of the message can decrypt the append cipher-text using the sender’s public key, and verify the integrity of the received message.

• The appended cipher-text served as a digital signature of the sender for the sent message


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RSA AlgorithmRSA Algorithm

R.L. Rivest, A. Shamir, and L. Adelman proposed their well-known RSA encryption algorithm.

In the RSA scheme, a message M is encrypted with the encryption key e by the function:

Cipher-text = E(M,e,N) = Me mod N Message = D(C,d,N) = Cd mod N The pair (e,N) is distributed as the public key while d is kept private. It can be

proved that given d and e are carefully selected such that:– d x e = 1 mod (p-1)(q-1)

and d is relatively prime to (p-1)(q-1), the functions D and E are the inverse of each other.


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RSA: An ExampleRSA: An Example

Pick p = 5, q = 7, z = 24, n = 35 Choose d = 5, relatively prime to z 1 mod z = 1, 25, 49, 73, 97, 121, 145... Pick e = 145 / d = 29 Public key (35, 29); Private key (35, 5) Encrypting message M = 10:

E(M) = 1029 mod 35 = 5 VERIFY: Decrypting cipher-text c = 5:

D(c) = 55 mod 35 = 3125 mod 35 = 10 = M In practice, much larger primes p, q are used The security provided by RSA relies on the fact that it is

computationally infeasible to factor a large number n to find out p, q, and hence z, e


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Attacks and Defenses on SIAS (1)Attacks and Defenses on SIAS (1)

• Scenario 1 - Modification of query products

• The list of products specified by user is stored as plain text

• Malicious host can easily spy out the data and change it

• Later hosts will response to such changes, and report wrong information

• This violates the integrity of queries


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• Scenario 2 - Modification of query quantities

• Similar to scenario 1

• This lead the later host to report wrong information


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• Scenario 3 - Spying out and modification of query results

• Agents carry query results in plain text

• Malicious hosts can spy out and modify the results that the agent has collected from previous hosts

• Such changes can favor the malicious hosts

• For example, a malicious host raises all the prices reported from previous hosts.


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• Scenario 4 - Modification of itinerary of agent

• Itinerary of an agent is accessible to hosts

• Malicious hosts can change the itinerary of an agent

• Agents may go to hosts that are not specified in itinerary

• Agents may skip hosts that are specified in itinerary


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• Hybrid Attacks

Host 1Malicious

HostHost N

Launch Server

• Can mix the above 4 attacks


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• Solution to Attack Scenario 1 & 2

• We introduce digital signature on the whole list of product IDs as well as the signature on the list of product quantities

• {Product ID list} => {Product ID list}sigA({Product ID list})

• {Quantity list} =>{Quantity list}sigA({Quantity list})


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• Solution to Attack Scenario 3

• We introduce RSA encryption algorithm on the results obtained from the Data Base server

• {Query result} => DA({Query result}sigH({Query result}))


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• Solution to Attack Scenario 4

• The Data Base server will sign the path of the agent to ensure the agent goes the right path

• EHN(EH(N-1)(…EH2(EH1(Itinerary at Host 1) Itinerary at Host 2) … Itinerary at Host N-1) Itinerary at Host N)


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• Introduce 2 new objects to support security measures

• RSA object ; and

• Key Server object


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• RSA object is the core of Secure SIAS design

• It helps to implement a public key infrastructure (PKI)

• It can encrypt a character string to ciphertext, and decrypt a ciphertext to a character string


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• Key Server object acts as a Certificate Authority (CA) of our PKI

• It accepts public keys from agents and hosts, and distribute them

• It uses RMI in transporting public keys

• Why not agent but RMI??

• Endless chain of security measures


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Host One(Concordia

Agent Transporter)

Host Two(Concordia

Agent Transporter)

Host N(Concordia

Agent Transporter)

Launch Server(RMI Server)

KeyServer(RMI Server)

Client Program(Java Applet)• A Secure SIAS


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Security Analysis on SIAS (1)Security Analysis on SIAS (1)

We have test times for SIAS to launch a single agent before and after the implementation of the security mechanisms.

Round trip times (RTTs) required for an agent to travel around are measured.

Queries of different sizes have been tested.


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Figure shows SIAS without security measures and attacks

• The RTT increases very slightly

• Overhead by each additional item in average is about 18.9 milliseconds.

• This can be explained by the small change in delay of database query with different query sizes.

Average Agent Travel l i ng Ti me

0

500

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1 2 3 4 5 6 7 8 9 10 11 12Number of i t ems

Average AgentTravel l i ng Ti me

mi l l i seconds


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0

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2000

3000

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mi l l i seconds

Figure shows SIAS with security measures implemented

• The RTT increases very fast and linearly with the size of query

• The overhead of each additional item is about 245 milliseconds, 13 times the overhead of the primary SIAS design

• This can be explained by the use of RSA algorithm

• It is time consuming to encrypt and decrypt data with long keys.

• Trade-off between performance and security for SIAS.


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• This graph and the next show SIAS with the simulation of malicious host’s attacks

• Both shows an agent takes more time to travel then the first figure.

• This suggests that the RTT may be used as a measure for tempering detection


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500

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1 2 3 4 5 6 7 8 9 10 11 12Number of i t ems


mi l l i seconds

Figure shows SIAS with simulation of attacks -

modification of product IDs


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0500

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1 2 3 4 5 6 7 8 9 10 11 12Number of i t ems


mi l l i seconds

Figure shows SIAS with simulation of attacks -

modifying itinerary


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SummarySummary

We studied the technology of autonomous mobile agents and discussed the problem of malicious hosts in a mobile agent system.

We implemented SIAS as a sample application of mobile agents, which reduces communication cost and allows delegation of tasks.

We addressed some security problems of malicious hosts in SIAS, and developed a primitive approach to protect the agents.

We analyzed the security of our approach, and believe it is strong enough for domestic purpose.

We measured the performance overhead of the security measures, see a trade-off between performance and security for SIAS, and learned that it takes time for a malicious host to attack an agent.


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Future WorkFuture Work

• We will implement payment method on SIAS

• We will scale up the current system

• We will continue to think of other security attack scenarios and corresponding solutions (such as multiple malicious hosts)

•We believe autonomous mobile agents would be an important technology in future distributed systems.


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ENDEND

THANK YOU!!

Documents

LYU9905 Security in Mobile Agent E-Commerce Systems