intelligent agents - security

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Intelligent Agents - Security

Katia Sycara

The Robotics Institute

email: [email protected]

www.cs.cmu.edu/~softagents

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Security for Electronic Commerce

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Insecure Internet

• The original Internet was designed for research, not as a commercial environment.

• The TCP/IP protocol suite used by all computers connected to the Internet is fundamentally lacking in security services.

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Internet Security Weaknesses - 1

• Confidentiality:

– Most lower layer protocols, including Ethernet, are “broadcast” in nature: machines connected to a LAN can eavesdrop on each other;

– Nodes lying on the path between two communicating parties can “eavesdrop” on traffic as it passes;

– Theft of account information, credit card numbers; theft of information-based products;

– Other info on “who talked to whom” (even without knowing the content involved) leads to loss of privacy;

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• Authentication:

– Virtually impossible to accurately determine whether the addresses in data packets are genuine or not;

– Hosts and users can spoof (impersonate) each other;

• Integrity:

– Packet contents: no service provided to authenticate the content of packets;

– Ex: modification of payee of a check; the value of a check.

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• Repudiation:

– parties may deny having participated in transaction, sent messages, given authorization, etc.;

• Hosts need to be protected as well; attacks targeted to retrieve cleartext information from poorly protected systems;

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Security Requirements for Commercial Transactions

• Confidentiality;

• Authentication;

• Data Integrity;

• Non-repudiation;

Security mechanisms based on cryptography

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Some Existing Solutions

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Cryptographic Building Blocks - 1

• Symmetric key cryptography:– Two parties share a common secret or key;– Keys are used to encrypt and decrypt messages;

Can be used for authentication with the help of a third party.

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Cryptographic Building Blocks - 2

• Public-key cryptographic:

– Matching private and public keys:

– Can be used to sign and verify signatures:

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Public Key Infrastructure• Ability to match specific keys with their owners:

– Public key certificates (Bind public keys to specific entities and allow for a third party to validate the binding);

– Ex: x509 certificate.

Can be used for encryption and decryption alone

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The Risks of Electronic Commerce - 1• The customers’ perspective:

– Stolen payment credentials + passwords;

– Dishonest merchants;

– Disputes over service qualities;

– Dishonest financial service providers;

– Inappropriate use of transaction details.

• The merchants’ perspective:– Forged or copied instruments;

– Disputed charges;

– Insufficient funds in customer accounts;

– Unauthorized redistribution of purchase items;

– Dishonest financial service providers;

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Not Everything has a Technical Solution

• There are problems where solutions can’t be enforced in advance, but where accepted practices solve the problem if followed:

– privacy protection;

– intellectual property rights;

– quality of service.

• These practices will usually be followed if:

– They are easy to follow;

– Social and legal enforcements.

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Other Weak Points

• Hardware;

• Operating systems;

• System configuration;

• System management;

• Compilers;

• Poorly written software;

• Application-level access control;

• User neglect

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Adding Security to Retsina

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Why do we need to worry about security?

• We want to deploy our system in open networks;

– Agents come and go => agents interact with strangers;

– Can agents be trusted? Can their deployers be trusted?

• Agents are expected to do more serious things. Ex:

– Getting info on your banking account;

– Carry out sales transactions.

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Assumptions we make

• Neither agents nor their deployers are trustworthy (They can misbehave):

– Agents may eavesdrop on communication between two other agents;

– An agent may masquerade as some other agent;

– Agents may not behave as expected (e.g., an agent may not want to pay for goods received).

• There must be a few, selected entities that can be trusted.

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Adding Security to Retsina (MAS in general)

• Prevent misbehaviors from happening + have recovery mechanisms if they happen:

– Identify different security issues that MAS face;

– Propose solutions for these problems;

– Design and implement a security infra-structure for Retsina.

• Focus: application-independent issues:

– Communication security: yes;

– Fair exchange in electronic sales: no.

• Approach: Standard security techniques used in distributed systems

– Authentication;

– Access control;

– etc.

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Security Threats in MAS

• System-level threats: Those that subvert inter-agent interactions, independently of the application a system is running.

– Untrustworthy ANSs and matchmakers;

– Untrustworthy application agents;

– Insecure communication channels.

• Application-level threats: Those that subvert the security of applications. They may exist even if the underlying system of agents is secure.

– Service providers that do not implement appropriate access control policies;

– Untrustworthy application agents.

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Our Solution (1)

• To guarantee the integrity of naming and matchmaking services:

– Include access control:

– <use> trusted ANSs and matchmakers!

• Make agents uniquely identifiable, and give them unforgeable proofs of identity:

– Prevents spoofing;

• Make deployers of agents liable for the actions of their agents:

– Agents are given proofs of identity only when deployers allow their own identities to be linked with those of their agents.

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Our Solution (2)

• Protect communication channels;

• Add access control mechanisms (which usually rely on the delegators’ Ids);

• Make agents prove that they are delegates of whom they claim to be.

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A Design of a Security Infra-structure for Retsina

Assumptions:

• Deployers have public key certificates binding their physical identities (SSN, company names, etc.) to their public keys;

• DCAs are assumed to exist (lie outside our security infra-structure);

• ANSs and matchmakers

– are trusted entities;

– their public keys are publicly known.

• The addresses of ANSs are publicly known.

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Public Key Cryptography

• Key pairs:

– Private keys: a ;

– Public keys: A ; pub(a)

• Digital signatures: (m)a

• Signature verification:

– Use A to verify (m)a

• Public key certificates:

– (Name, Public key)ca

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Giving Identities to Agents + Establishing Liability (1)

1. Choose an Agent ID AID

2. Generate a public key pair {a, pub(a)}

3. m1=(certify AID,pub(a),t)d

4. Verify the validity of the request

5. Generate m2=ACA-signed certificate binding pub(a) to AID

6. Creates an entry [D’s public key certificate, m1] in the certification DB

8. Verify the signature in m2 with ACA’s public key.

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Giving Identities to Agents + Establishing Liability (2)

• Agents are given:

– a public key certificate, and

– a matching private key.

• The certification process:

– certification can be requested only by deployers who can prove their own identities => make the deployer aware of his or her liabilities.

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Revoking an Agent’s Public Key

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Registering at an ANS

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Unregistering at an ANS

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The Lookup Protocol

Agents are identified by their keys, and not their names!!

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Matchmaker Protocols

• Very similar to ANS protocols;

• Differences:– Physical addr may not be shared by more than one agent; capabilities

may;

– Agents use ANSname.Agentname to register with the matchmaker;

– The lookup protocol:

1. CAP

2. [CAP, {[ANS-x1.AID1,CERT1],… [ANS-xn.AIDn, CERTn]}, T]mm

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Secure Communication Channels

• SSL (Netscape’s Secure Socket Layer protocol);

• Why?

– Keep communication security transparent from the application;

– Off-the-shelf trustworthy technology (extensible too).

• Implementation:

– Local effort: at the Communicator.

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Secure Delegation + Access Control

• Knowing who is the delegator may be necessary or desirable;

• Original design: Have the agent know the secret key of its deployers;

• Weaknesses:

– Agents should not know such important secrets;

– Sometimes they do not even have to know (ex: PIN);

– Should have a “weaker,” “temporary” solution.

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Some Interesting Pages

• http://microsoft.com/security/tech/certificates/formats.asp

– Some introductory material on standards for cryptographic object;

• http://security.dstc.edu.au/projects/java/release3.html

– Info on a real-world security package (can download the code and play);

• Communications of the ACM - June 1996, volume 39, Number 6

– An issue dedicated to EC; from which the article is extracted.

intelligent agents - security

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