Computer Science 725 – Software Security Presentation “Decentralized Trust Management” Decentralized Trust ManagementDecentralized Trust Management M. Blaze, J. Feigenbaum, J. Lacy, IEEE Symposium on Security and Privacy, pp ,

Summary Identify Trust Management as a distinct and important component in network security Identify Trust Management as a distinct and important component in network security Review of 2 existing systems Review of 2 existing systems Present a new comprehensive approach to this problem Present a new comprehensive approach to this problem Describe a prototype (PolicyMaker) which implements this new approach Describe a prototype (PolicyMaker) which implements this new approach

What is Trust Management? Policy (a banking system requires at least k officers to approve a loan of $10,000) Policy (a banking system requires at least k officers to approve a loan of $10,000) Credentials (enable an employee to prove he can be counted as 1 out of k approvers) Credentials (enable an employee to prove he can be counted as 1 out of k approvers) Trust (enable the bank to specify who may issue such credentials) Trust (enable the bank to specify who may issue such credentials) Public Key

Principles of our approach Unified mechanism Unified mechanism A common language is provided for policies, credentials, and relationshipsA common language is provided for policies, credentials, and relationships Flexibility Flexibility The system is rich enough to support potentially complex relationships in large networksThe system is rich enough to support potentially complex relationships in large networks Locality of control Locality of control Each party in the network can independently decide whether to accept the credentials presentedEach party in the network can independently decide whether to accept the credentials presented Separation of mechanism from policy Separation of mechanism from policy The mechanisms for verification does not depend on the credentials themselvesThe mechanisms for verification does not depend on the credentials themselves

Review of Existing Systems What are some potential issues with this system? PGP framework uses “ key certificates” in which trusted third parties (C, D) signs copies of a public key to be distributed PGP framework uses “ key certificates” in which trusted third parties (C, D) signs copies of a public key to be distributed X.509 framework uses a similar system, but also postulates that public keys are only obtained from official “certifying authorities” (C, D) X.509 framework uses a similar system, but also postulates that public keys are only obtained from official “certifying authorities” (C, D) Specify trust Public Key signed by C Public Key signed by D Etc … B accepts Public Key if its trust value is high enough

PolicyMaker Approach 1 Obtain certificates, verify signatures on certificates and on application request, determine public key of original signer(s) 2 Verify that certificates are unrevoked 3 Find “trust path” from trusted certifier to certificate of public key in question 4 Extract names from certificates 5 Lookup names in database that maps names to the actions that they are trusted to perform 6 Determine whether requested action is legal, based on the names extracted from certificates and whether the certification authorities are permitted to authorize such actions according to local policy. 7 Proceed if everything appears valid PolicyMakerSubmit request, certificates, and description of local policy to local “trust management engine”

The PolicyMaker System What are some potential issues with this system? An independent trust management engine to be used either as a linked library (within systems) or daemon (background application) An independent trust management engine to be used either as a linked library (within systems) or daemon (background application) Called using action query strings Called using action query strings Extendable to allow for external verification of signatures Extendable to allow for external verification of signatures

Comments The idea behind this paper is good The idea behind this paper is good Encapsulation of trust managementEncapsulation of trust management Better security provided by consolidated systemBetter security provided by consolidated system The idea presented is more difficult to implement The idea presented is more difficult to implement Dedicated trust management engine and parser is more difficult to implement than certificate based systemDedicated trust management engine and parser is more difficult to implement than certificate based system Only applicable to large commercial applicationsOnly applicable to large commercial applications Protype is already made. Protype is already made.Questions?