delegation of authority

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

2. 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) Copyright 2006 University of Kent

3. 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? Copyright 2006 University of Kent

4. 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 Copyright 2006 University of Kent

5. 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 Copyright 2006 University of Kent

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

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

8. 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 Copyright 2006 University of Kent

9. 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 Copyright 2006 University of Kent

10. 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 Copyright 2006 University of Kent

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

12. 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? Copyright 2006 University of Kent

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

14. 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) Copyright 2006 University of Kent

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

16. 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 Copyright 2006 University of Kent

17. 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 Copyright 2006 University of Kent

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