LYU9905 Security in Mobile Agent E-Commerce Systems

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LYU9905Security in Mobile Agent E-Commerce
Systems

• Prepared by Wong Ka Ming, Caris
• Wong Tsz Yeung, Ah Mole
• Supervisor LYU Rung Tsong Michael

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Outline (1)

• Introduction
• What is mobile agent?
• Project Overview
• Overview of SIAS Shopping Information Agent
  System
• System Details
• Implementation of SIAS
• Security Measure of SIAS
• Security Attack and Defense Scenarios in SIAS

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Outline (2)

• Agent Encryption Technique
• Diffie-Hellman Key Exchange
• Fault Tolerance of SIAS
• Monitor Program
• Connection Availability Detection
• Security Analysis of SIAS
• Trade-off between security performance in SIAS
• Project Review Conclusion
• Q A Session

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Introduction (1)

• What is mobile agent?
• A mobile agent is a software which can
  autonomously do the job for us.
• For e-commerce, the aim of mobile agent
  technology is to provide an autonomous buying and
  selling environment.
• Unlike the traditional client/server paradigm,
  which require continuous network connection,
  mobile agent make use of the mobile code
  paradigm, which can closed the connection once
  the agent is launched.

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Introduction (2)

• What is mobile code paradigm?
• Consider the applet
• The code is downloaded from the web server to the
  client side and runs in the client side through
  the web browser
• Such strategy is called code on demand, which
  means the code are moving across the machine
  passively when demanded
• Mobile code paradigm is little bit different in
  which the code will actively move from one host
  to another

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Introduction (3)

• What is the advantage of mobile agent?
• It can be able to communicate with other agents,
  so it is suitable for some system, such as Stock
  Broker System.
• It is mobile and able to travel from one host to
  another, so it is very suitable for mobile
  computing, in which the machine cannot be always
  connected to the network.
• It reduces the network load and it also overcome
  network latency.
• It is autonomous, has control over its own
  actions, which means it can adapt to changes
  dynamically.
• Thus, it is robust and fault-tolerant

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Project Overview (1)

• Our project is aimed on designing a web-based
  e-commerce system building on top of mobile agent
  technology.
• In the last semester, we have developed the SIAS
  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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Project Overview (2)

• Whats System does?

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Implementation of SIAS (1)

• 4 main objects in implementation
• Agent
• Database Server
• Launch Server
• Client Program

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Implementation of SIAS (2)

• Agent
• Retrieves products information from Database
  Server to clients
• Launch Server
• A gateway between Agent System and Client Program
• Instantiates and launches Agent whenever receives
  client requests
• Receives Agent whenever Agent travels back

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Implementation of SIAS (3)

• Database Server
• Receives incoming Agent whenever an Agent arrives
• Retrieves product information for the incoming
  Agent
• Client Program
• A Java Applet runs on Web Browser
• Sends requests to Launch Server
• A Multi-threaded program, can handle multiple
  requests simultaneously

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Implementation of SIAS (4)

• System Configuration
• One Launch Server
• 26 Database Servers
• Client Program uses Netscape Communicator 4.5 or
  above

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Implementation of SIAS (5)
Database Server 1
Database Server 2
Database Server N
Agent retrieves product information from Database
Server N
Database Server 2 receives Agent and Agent
retrieves product information
Agent travels through the network until it
arrives at Database Server N
Agent retrieves product information from Database
Server 1
Agent calculates the cheapest price combination
Launch Server create an Agent
Agent goes to Database Server 1
Launch Server sends out Agent
Launch Server initializes the Agent
Agent arrives at Database Server 1
Database Server 1 sends out Agent
Agent travels back to Launch Server
Launch Server
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Attacks and Defenses on SIAS (1)

• Scenario 1 - Modification of query products ID
• 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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Attacks and Defenses on SIAS (2)

• Scenario 2 - Modification of query quantities
• Similar to scenario 1
• This leads the later host to report wrong
  information

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Attacks and Defenses on SIAS (3)

• 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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Attacks and Defenses on SIAS (4)

• 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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Attacks and Defenses on SIAS (5)

• Hybrid Attacks
• Can mix the above 4 attacks

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Attacks and Defenses on SIAS (6)

• Solution to Attack Scenario 1 2
• We introduce encryption on the whole list of
  product IDs as well as the list of product
  quantities

• Product ID list changed to EA(Product ID
  list)

• Product Quantity list changed to EA(Product
  Quantity list)

Key Ex(Y) CipherText of Plain Text Y encrypted
by private key of entity X Dx(Y)
Plain Text of CipherText Y decrypted by public
key of entity X A Agent
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Attacks and Defenses on SIAS (7)

• Solution to Attack Scenario 3
• We introduce RSA encryption algorithm on the
  results obtained from the Database Server

• Query result changed to EH(Query result)

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Attacks and Defenses on SIAS (8)

• Solution to Attack Scenario 4
• The Database Server will sign the path of the
  agent to ensure the agent goes the right path

New attribute for Agent Encrypted_Itinerary Encry
pted_Itinerary EH1(Next Host at Host H1)
EH2(Next Host at Host H2) ... EHn(Next Host at
Host Hn) At Launch Server, we compare original
itinerary to DH1(EH1(Next Host at Host H1))
DH2(EH2(Next Host at Host H2)) ... DHn(EHn(Next
Dost at Host Hn))
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Attacks and Defenses on SIAS (9)

• Introduce 2 objects to support security measures
• RSA object and
• Key Server object

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Attacks and Defenses on SIAS (10)

• 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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Attacks and Defenses on SIAS (11)

• 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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Attacks and Defenses on SIAS (12)

• A Secure SIAS

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Agent Encryption (1)

• For Java, the bytecode can easily be decompiled
  by decompiler such as mocha and any decompiling
  software.
• Therefore we should obscure a mobile agents code
  to make it hard to reverse engineer.
• We use agent encryption to encrypt the mobile
  agent before it travels to one host to another
  host.
• After it reaches the destination host, it will
  then be decrypted as a normal mobile agent and
  starts its normal execution.

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Agent Encryption (2)

• Because the agent is encrypted, the ability of
  traveling from host to host will then be done by
  an envelope agent.
• An envelope agent is a normal agent will
  encapsulate the encrypted agent.
• It travels to hosts on behalf of the buying
  agent. It aims to protect the buying agent during
  transmission.

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Agent Encryption (3)

• Therefore before envelope agent moves to the next
  host, it will encrypt the buying agent .
• When it reaches the destination host, it will
  decrypt the buying agent and execution of the
  agent will then be performed as normal after
  decryption.

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Agent Encryption (4)

• We found that our original RSA algorithm cannot
  encrypt the agent object.
• Thus, we have to try another method
• we have used symmetric key approach
• We make use of the Diffie-Hellman Key Exchange
  for exchanging the symmetric key between two
  hosts.

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Agent Encryption (5)

• Diffie-Hellman Key Exchange
• It is a key exchange technique which enables two
  users to exchange a key securely without actually
  transmitting the key in the network..
• Therefore attackers cannot get the symmetric key
  by tapping the network.
• It can then be used for subsequent encryption of
  message.
• It depends for its effectiveness on the
  difficulty of computing discrete algorithm

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Agent Encryption (6)

• Diffie-Hellman Key Exchange (cont)

• Under its scheme, there are two publicly known
  numbers a prime number n and an integer g that
  is a primitive root of n

• Suppose hosts A and B wish to exchange a key

• Host A selects a random integer x lt n and
  computes X gxmod n.

• Similarly, host B independently selects a random
  integer y lt n and compute Ygymodn.

• Each side keeps x and y be private and makes X
  and Y available publicly to the other side.

• Host A computes the key as K Yxmodn and host B
  computes the key as K Xymodn.

• These two calculations produce the same result
  and act as the symmetric key

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Agent Encryption (7)

• Thus, the two sides have exchanged a secret key.
• Furthermore, because x and y are private, an
  opponent only has the following ingredients to
  work with g, n, X and Y.
• Thus, the opponent is forced to take a discrete
  logarithm to determine the key.
• For example, attacking the secret key of host B,
  the opponent must compute y using Y, g and n
  which is computationally difficult to do so.

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Agent Encryption (8)

• Using Diffie-Hellman Key Exchange technique, we
  can use the symmetric key to encrypt the agent.
• We use the bitwise XOR to encrypt and decrypt the
  agent
• When the agent wants to travel to next host, it
  first get the public key of the next host and
  generate the symmetric key using the private key
  of the host that it resides. Then it will encrypt
  itself using the symmetric key.
• When the agent reaches the destination host, it
  will get the public key of the previous host and
  decrypt itself using the secret key the
  destination host.

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Agent Encryption (9)

• To implement agent encryption for our system
  SIAS, we have introduce three more objects to our
  system, namely the Encrypt Agent which is the
  envelope agent encapsulating the buying agent,
  the DHKey, and the DHKey Server.
• The Encrypt Agent is an agent which contains the
  encrypted buying agent. It acts as an envelope
  agent and travel to hosts on behalf of the buying
  agent.
• It aims to protect the buying agent during
  transmission.

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Agent Encryption (10)

• Why use Encrypt Agent to enclose buying agent?
• Since the buying agent is encrypted during
  transmission, the agent would then be unable to
  travel to the next host.
• It is because the sending host is unable to
  recognize the encrypted code of the agent and
  therefore the agent is not executable at all
  after encryption.
• Encrypt Agent will act on behalf of the buying
  agent to travel around the hosts. It encapsulates
  the buying agent and move to the next host.
• Hosts will recognize the Encrypt Agent and do the
  execution (i.e. encryption and decryption).

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Agent Encryption (11)

• The DHKey contains the private key and the pubic
  key for Diffie-Hellman Key Exchange.
• It has two methods, namely encrypt and decrypt
  for agent encryption and decryption.
• These two methods perform their operation by
  making use of two internal method toByteArray
  and toObject.
• The method toByteArray can change the object into
  byte array which can then be used for symmetric
  encryption algorithm.
• The method toObject can change the byte array
  back to object which is the decrypted agent.

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Agent Encryption (12)

• DHKey Server is similar to the Key Server.
  Instead of storing RSA public keys, it stores the
  public keys of Diffie-Hellman Key Exchange
  Algorithm.
• When the system start up, each host and server
  will send a public key to the DHKey Server. The
  keys are then store in it.

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Agent Encryption (13)

• When an Encrypt Agent reach a host, it needs the
  public key of the previous host for agent
  decryption. It will invoke the method of the
  DHKey Server for the public key.
• Similarly, when an Encrypt Agent want to moved to
  the next host, it will invoke the same method to
  get the public key of the next host for agent
  encryption.
• The connection between the Database Servers or
  Launch Server and the DHKey Server is done by
  Java RMI.

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Agent Encryption (14)
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Reliability of SIAS (1)

• Our system is highly dependent on Concordia API
• Faults occur in Concordia API cannot be avoided
• In Concordia architecture, an agent will lose if
  anyone of the destinations of agent does not
  exist
• This introduces data loss
• To prevent data loss, fault-tolerance design is
  needed

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Reliability of SIAS (2)

• Whenever a component fails, we restart it
• Component restart strategy
• Database Server fails
• restart the failed host
• Launch Server fails
• A whole system recovery
• Launch Server loses backups for security measures
• Key / DHKey Server fails
• A whole system recovery
• Public keys lost due to failures cannot be
  recovered

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Reliability of SIAS (3)

• We design two strategies in our fault-tolerance
  design
• Logging System
• Connection Availability Detection, CAD

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Reliability of SIAS (4)

• Logging System
• Maintain Log File of each component
• Each line of a log file contains state as well as
  message of the component

...... initialization Listening to Incoming
Agents handle agent Agent arrived handle
agent Error in connecting to SQL Server ......
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Reliability of SIAS (5)

• With Logging System, we can successfully restart
  failed components
• However, we cannot prevent data loss
• Agent can still reach failed components
• We need additional features to prevent data loss

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Reliability of SIAS (6)

• Connectivity Availability Detection, CAD
• A mechanism analogous to PING

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Reliability of SIAS (7)

• Weakness in our design
• Data loss if failures occur at Launch Server, Key
  Server or DHKey Server because of a whole system
  recovery
• Data loss if the component that the agent resides
  fails

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Reliability of SIAS (8)

• Implementation I
• We introduce a Monitor Program to our system
• The Monitor Program is responsible for Logging
  System as well as CAD

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Reliability of SIAS (9)
Monitor Program
If a server fails
Server restarts
server
server
server
server
It does not response to ping signal

• A forever loop is used to check the servers

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Reliability in SIAS (10)

• A Ping signal is a combination of two kinds of
  inspections
• A Log File inspection
• It looks for Error Messages in a log file
• A RMI binding detection
• It looks for a RMI address binding
• Each component has to bind a RMI address
• Failure will unbind a RMI address

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Reliability in SIAS (11)

• Implementation II
• Modify Launch Server and Database Servers
• Embed CAD features in Launch Server and Database
  Servers

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Reliability in SIAS (12)
Agent sends checking signals to Server B until it
replies
Agent arrives at Server A
Agent travels to Server B
Agent arrives at Server B
If Server B is down
Restart signal sent by Monitor Program
Agent travels to Server B
Agent arrives at Server B
This can guarantee that agent can travel to its
destination without any data loss
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Security Analysis on SIAS (1)

• The security of the additional measures lies
  mainly on the introduction of a Key Server that
  facilitates the use of public key cryptography.
• Assuming the Key Server as well as communication
  channel with the Key Server are secure enough,
  and the keys are managed properly, the prevention
  of modification of the signed product and
  quantity lists of an agent by a malicious host is
  supported by the security of the RSA encryption
  algorithm.

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Security Analysis on SIAS (2)

• Time complexity for breaking the RSA cryptosystem
  depends on the length of the key in number of
  bits.
• The longer the key is, the more secure the system
  would be.
• In our implementation, we have chosen a key
  length of 128 bits.
• This would be sufficiently secure for our
  security purpose.

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Security Analysis on SIAS (3)

• We have tested the times for SIAS to launch a
  single agent before and after implementation of
  the security mechanisms.
• To evaluate the performance overhead introduced,
  we have tested the times for SIAS to launch a
  single agent with and without security measures.
• Round trip times (RTTs) required for an agent to
  travel around an electronic market, consisting of
  26 hosts, are measured under different
  situations.
• We will measure the performance overhead of the
  security measure, such as encrypting the agent,
  see the trade-off between performance and
  security for SIAS.

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Security Analysis on SIAS (4)

• RTT for an agent to travel in SIAS changes more
  or less linearly over the number of hosts.
• This is due to the additional time to travel an
  additional host, and the overhead for each
  additional host is more or less the same.
• RTT is also linearly increasing as the number of
  products of the query increases because of the
  increases in number of database transactions and
  time to transport an agent.

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Security Analysis on SIAS (5)

• When security is enforced, the RTT increases. For
  the maximum number of hosts of 26, and maximum
  size of query of 90 products, the RTT increases
  by 100 seconds, from 230 sec to 350 sec. This can
  be explained by the extensive use of the RSA
  algorithm to encrypt and decrypt each item.
• We see a trade-off between security and
  performance in SIAS.

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Conclusion (1)

• We studied the technology of autonomous mobile
  agents and discussed the problems 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 found that security problems of malicious
  hosts in SIAS is a main concern.
• Therefore, we had developed a primitive approach
  to protect the agents such as data encryption and
  agent encryption.

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Conclusion (2)

• We analyzed the security of our approach, and
  believe it is strong enough for domestic purpose.
• We had measured the performance overhead of the
  security measures and we saw a trade-off between
  performance and security for SIAS. We learnt that
  it takes time for a malicious host to attack an
  agent.
• Therefore we can set a time limit for detecting
  the malicious host attacking the agent. If the
  agent returns back in a time longer than the time
  limit, it is probably that the agent was attacked
  by the malicious host.

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Conclusion (3)

• We analyzed the reliability of SIAS and implement
  a fault-tolerance design of SIAS.
• We believe that mobile agent technology will be a
  new trend in electronic commerce technology.

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Thank You!