Privilege Management Infrastructure PMI

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Privilege Management Infrastructure (PMI)

• Joe Oldford
• EE 579
• 02 Mar 06

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Mary Queen of Scots
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Overview

• PKI vs PMI
• Attribute Certificates
• Delegation
• Types of Attribute Certificates
• Extending X.509 Role Models
• Summary

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PKI Review

• With a high degree of assurance (warm fuzzy
  feelings) PKI offers
• Identification
• Authentication
• Confidentiality
• Non-repudiation
• But what about managing approval or privilege to
  perform a task

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What is a Privilege Management Infrastructure

• A privilege management infrastructure is a
  mechanism that can be used to support business
  authority structures (Role Based)
• PMI is an aspect of PKI and requires underlying
  services for the management of public key
  certificates
• A PMI should support an organization's authority
  structure

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When to use a PMI

• X.509 PKCs have some support for Privilege
  management through subject attributes but this
  support breaks down when
• The CA is not responsible for assigning
  privileges
• There are a number of privileges to be assigned
  by different CAs
• PKC and privilege validity periods differ

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PKI vs PMI
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Attribute Certificates

• ACs are digital certificates that serve
  primarily to enable verifiers to establish
  attributes other than identity
• ACs do not provide authentication, so they must
  be used in conjunction with an existing PKI
• ACs are presented to a privilege verifier who
  acts like a reference monitor before access to
  the object is granted

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Types of Attribute Certificates

• Role Specification Certificates (RSC)
• Specific privileges that are associated with a
  particular role
• Role Assignment Certificates (RAC)
• Entities are assigned to the role specified in
  the RSC through the use of RACs

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Delegation

• Delegation is the conveyance of a privilege from
  a subject who holds a privilege to a subject who
  doesnt

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How this all works.
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Extending the X.509 Roles Model

• X.509 offers no support for complex roles,
  however, recent research proposes a way to
  accomplish such roles.
• Allow super roles by having role attributes
  within a role specification certificate pointing
  to another role specification certificate

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What??..
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Advantages

• Convenience super roles can be easily built by
  combining elementary roles
• Allows businesses to tailor their PMI to their
  authority structure
• Reuse elementary roles can reused by several
  super roles
• Automatic updating any changes made to
  elementary roles would automatically percolate
  upwards

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Disadvantages

• Roles have to be defined with care to ensure the
  super role does not inherit a privilege that role
  is not entitled to

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Conclusion

• A PMI is to authorization what a PKI is to
  authentication
• PMI and PKI together form a system that offers a
  high degree of assurance for both IA and access
  control
• The roles model in the current X.509 standard is
  compatible with the concept of Role Based Access
  control
• The extended interpretation allows for greater
  flexibility and hence usability of the X.509
  standard

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References

• Knight and Grandy, Scalability Issues in PMI
  Delegation., 1st annual PKI Research Workshop
  Proceedings, Apr 2002
• D. Chadwick, The X.509 Privilege Management
  System., The European Journal for the
  Informatics Professional, Vol IV Issue 4, Aug 2005

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Questions?