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 owner’s 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 Agent’s 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 Agent’s 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 customer’s 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