1. 21 June 2006Copyright 2006 University of Kent1 Delegation of Authority (DyVOSE project) David Chadwick University of Kent

2. 21 June 2006Copyright 2006 University of Kent2 What is Delegation of Authority? Allowing someone to act on your behalf to perform tasks (consume resources) that are available to you Delegator should be empowered to delegate to anyone he needs to, subject to certain organisation controls (i.e. the organisation’s Delegation Policy)

3. 21 June 2006Copyright 2006 University of Kent3 How do you delegate to others today? To enter your house and fetch something –If your house if locked? To use your PC –If it is protected by a username and password? To withdraw money from your bank account –Using an ATM?

4. 21 June 2006Copyright 2006 University of Kent4 What is the problem with these existing delegation mechanisms? The other person usually masquerades as you, or impersonates you There is no control on what they can do –Anything you can do, they can do

5. 21 June 2006Copyright 2006 University of Kent5 What is a better solution? The delegate should act in his own name, not in yours –Then a full audit trail can be kept of who did what The delegate should have limited authority –So that you can delegate a fraction of your powers

6. 21 June 2006Copyright 2006 University of Kent6 Resource Owner “I authorise this Privilege Holder to use this resource in the following ways” signed The Resource Owner Privilege Holder “I delegate authority to this End User to use this resource in this limited way” signed The Privilege Holder End User (Privilege Holder) Assigns privilege to Delegates privilege to “Can I use the Resource” Assigning and Delegating Privileges in Organisations

7. 21 June 2006Copyright 2006 University of Kent7 Privilege Checking in Organisations “Please purchase this product from company X” signed the End User End User (Privilege Holder) Privilege Verifier Q. “Is this user authorised to purchase these goods?” Issues a command (Asserts Privilege)

8. 21 June 2006Copyright 2006 University of Kent8 Access Control Usually based on access control lists –This list of users can do these things Examples Ed and Jake can read the exam results file on the Kent University website Jo and Zoe get 10% discount when electronically shopping at Tescos PROBLEMS You need to know the names of all the users Very difficult to scale to Internet proportions where there are millions of users

9. 21 June 2006Copyright 2006 University of Kent9 Role Based Access Control Users are given roles (or attributes) Holders of attributes are given access permissions Examples Ed and Jake are Students at Kent University Students at Kent University can read the exam results file on the website Jo and Zoe are Tesco Clubcard holders Tesco Clubcard holders get 10% discount when shopping electronically at Tescos

10. 21 June 2006Copyright 2006 University of Kent10 Delegation of Authority with Role Based Access Controls Users who have attributes (or roles) can delegate these to other users Users can also delegate subordinate roles E.g. professor is superior to academic staff is superior to PG student is superior to UG student A professor can delegate the academic staff role, or the PG student role or the UG student role so as to delegate partial privileges

11. 21 June 2006Copyright 2006 University of Kent11 Assigning Privileges Electronically - using X.509 Attribute Certificates Bill Alice Bob SOA AA Issues AC to Issues AC to End Entity AC Points to issuer Points to holder SOA = Source of Authority AA = Attribute Authority An Attribute Certificate is a digitally signed electronic document that says that this holder has been given these attributes by this issuer

12. 21 June 2006Copyright 2006 University of Kent12 Main points of this system Every delegated attribute (or role) is digitally signed so that it cannot be tampered with or altered Each attribute certificate says who the delegator and delegatee are (issuer and holder) Very secure way of delegating authority BUT – each user needs a digital signing key and digital certificate How many of you have digital certificates and signing keys?

13. 21 June 2006Copyright 2006 University of Kent13 Bill Alice Bob SOA AA End Entity Issues AC to Issues AC to Delegation Issuing Service (DIS) Issues AC to AC Points to issuer Points to holder Points to Issued On Behalf Of The Delegation Issuing Service

14. 21 June 2006Copyright 2006 University of Kent14 Advantages of the Delegation Issuing Service Users don’t need to have signing keys since the DIS signs the Attribute Certificates on their behalf The DIS keeps a central record (audit trail) of who has delegated what to whom The DIS has a Delegation Policy to control who can delegate what to whom The process of privilege checking is very efficient since all ACs are issued by the DIS (and not by lots of different users)

15. 21 June 2006Copyright 2006 University of Kent15 LDAP server Authenticate the User DIS IssueAC Web service interface publishAC PERMIS Decision Engine Sign AC Request Authorisation Delegation Policy Our DIS System

16. 21 June 2006Copyright 2006 University of Kent16 The Delegation of Authority Demo Public web page Secure web page only available to users with Researcher role Role Hierarchy Anyone with Admin or Researcher role can delegate Researcher role to anyone else in Staff domain

17. 21 June 2006Copyright 2006 University of Kent17 Delegation Demo (cont) Simon is already a researcher Simon would like to delegate to Sarah to access his resource Simon accesses the Delegation Issuing Service and assigns the Researcher role to Sarah Sarah can now access the resource Simon then revokes the researcher role Sarah no longer has access

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