Mobile Agent Security

1
Mobile Agent Security

• John Russell
• Anthony Pringle

2
What is an Agent?

• An autonomous program that migrates across
  different execution environments
• A very, very bad man

3
Examples and Applications

• Searching and filtering
• Information Retrieval
• Flight schedules
• best prices
• automated shopping

4
Advantage of Mobile Agents

• They move the computations closer to the
  resources they need to access
• Reduces network communication, bandwidth and
  latency

5
Security Concerns

• Two broad categories
• Protecting the host from malicious agents
• Protecting the agent from malicious hosts
• Detection of agent tampering
• Prevention of agent tampering

6
Classification of Malicious Host Security Threats

• Integrity
• Information Modification
• Integrity Interference
• Availability
• Denial of service
• Delay of service
• Transmission Refusal
• Confidentiality Attacks
• Eavesdropping
• Theft
• Reverse Engineering

7
Privacy Concerns

• Agent carries the owners private key to
  authenticate transactions
• Possible problems?
• The Agent may need to use the secret in public
• Example to compute a signature on an order form
• A malicious host could steal the Agents key and
  sign unauthorized transactions
• Goal a mechanism for the Agent to produce
  digital signatures without disclosing its secret

8
Computing with Encrypted Functions

• Prohibits the host from learning details of the
  Agents secret.
• Basic Procedure
• Alice encrypts a function f
• Alice creates the program P(E(f))
• Alice sends P(E(f)) to Bob
• Bob executes P(E(f)) at x
• Bob replies to Alice with P(E(f))(x)
• Alice decrypts P(E(f))(x) to obtain f(x)

9
Undetachable Signatures

• Although hidden, the signing routine can still be
  abused to sign arbitrary documents
• We need a way to bind the signature routine to a
  specific transaction
• We call this an undetachable signature

10
A Secure Implementation of Undetachable Signatures

• In 2000, Burmester et. al. described a
  non-interactive CEF undetachable signature
  scheme.
• Uses exponential functions as encrypting function
• Based on RSA
• Provably secure

11
Preparing the Agent

• The customer gives to the agent the undetachable
  signature function pair
• f() h() mod n where h hash(C, req_C)
• fsigned k() mod n, where k hd mod n is the
  customers RSA signature of h.
• The agent migrates to the server with the pair
  (f(), fsigned) as part of its code, and (C,
  req_C) as part of its data

12
Undetachable Signatures
13
Undetachable Signatures

• A malicious host can produce a signature that
  includes a bogus bid from the server, but the
  signature will be invalid
• Efficient the RSA implementation takes only
  three exponentiations
• Authentication is preserved because the signature
  cannot be applied to an arbitrary message

14
Questions?

• Please direct all questions to Dr. Burmester

15
References

• Sander and C.F. Tschudin. Protecting mobile
  agents against malicious hosts. In G.
  Vigna,editor, Mobile agent security, number 1419
  in Lecture Notes in Computer Science, pages
  44-60.Springer-Verlag, Berlin, 1998
• P. Kotzanikolaou, M. Burmester, and V.
  Chrissikopoulos. Secure transactions with mobile
  agents in hostile environments, Information
  Security and Privacy Proceedings of the 5th
  Australasian Conference -- ACISP 2000, number
  1841 in Lecture Notes in Computer Science, pages
  289-297. Springer-Verlag, Berlin, 2000.
• E. Bierman and E. Cloete. Classification of
  Malicious Host Threats in Mobile Agent Computing.
  Proceedings of SAICSIT 2002, Pages 141-148