Confidentiality, Privacy and Trust - II

Dr. Bhavani Thuraisingham

The University of Texas at Dallas

Lecture #13

October 8, 2008

Outline of the Unit

Need to Know to Need to Share RBAC, UCON, RBUC Dissemination Rick based access control Trust Management/Credential/Disclosure Semantic Web and Trust Directions Major conferences for Policy and Access Control:

- IEEE Policy Workshop

- ACM SACMAT

Need to Know to Need to Share

Need to know policies during the cold war; even if the user has access, does the user have a need to know?

Pose 9/11 the emphasis is on need to share

- User may not have access, but needs the data Do we give the data to the user and then analyze the

consequences Do we analyze the consequences and then determine the

actions to take Do we simply not give the data to the user What are risks involved?

RBAC Access to information sources including structured and

unstructured data both within the organization and external to the organization

Access based on roles Hierarchy of roles: handling conflicts Controlled dissemination and sharing of the data

RBAC (Sandhu)

UCON RBAC model is incorporated into UCON and useful for

various applications

- Authorization component Obligations

- Obligations are actions required to be performed before an access is permitted

- Obligations can be used to determine whether an expensive knowledge search is required

Attribute Mutability

- Used to control the scope of the knowledge search Condition

- Can be used for resource usage policies to be relaxed or tightened

UCON (Sandhu)

Role-based Usage Control (RBUC)

RBAC with UCON extension

Operations(OP)

Authorizations

(A)

●●

Sessions(S)●

Object Attributes (OA)

Obligations(B)

Conditions(C)

Usage Decisions

Roles(R)

Users(U)

Objects(O)

Session Attributes (SA)

User-Role Assignment (URA)

Pemission-Role Assignment(PRA)

Pemissions(P)

Role Hierachy(RH)

User Attributes (UA)

RBUC in Coalition Environment

professor

professor

professorprofessor

A

B(trustworthy)

C(semi-trustworthy)

D(untrustworthy)

Student record

•The coalition partners maybe trustworthy), semi-trustworthy) or untrustworthy), so we can assign different roles on the users (professor) from different infospheres, e.g.•professor role, •trustworthy professor role, •semi-trustworthy professor role,•untrustworthy professor role.

•We can enforce usage control on data by set up object attributes to different roles during permission-role-assignment, •e.g. professor role: 4 times a day,trustworthy role: 3 times a daysemi-trustworthy professor role: 2 times a day,untrustworthy professor role: 1 time a day

Dissemination Policies

Release policies will determine to whom to release the data

- What is the connection to access control

- Is access control sufficient

- Once the data is retrieved from the information source (e.g., database) should it be released to the user

Once the data is released, dissemination policies will determine who the data can be given to

- Electronic music, etc.

Risk Based Data Sharing/Access Control/Trust

What are the risks involved in releasing/disseminating the data Risk modeling should be integrated with the access control model Simple method: assign risk values Higher the risk, lower the sharing What is the cost of releasing the data? Cost/Risk/Security closely related

Trust Management Trust Services

- Identify services, authorization services, reputation services

Trust negotiation (TN)

- Digital credentials, Disclosure policies TN Requirements

- Language requirements Semantics, constraints, policies

- System requirements Credential ownership, validity, alternative negotiation

strategies, privacy Example TN systems

- KeyNote and Trust-X (U of Milan), TrustBuilder (UIUC)

Trust Management

The problem: establishing trust in open systems

Mutual authentication

- Assumption on the counterpart honesty no longer holds- Both participants need to authenticate each other

Interactions between strangers

- In conventional systems user identity is known in advance and can be used for performing access control- In open systems partecipants may have no pre-existing relationship and may not share a common security domain

Trust Negotiationmodel

A promising approach for open systems where most of the interactions occur between strangers

The goal: establish trust between parties in order to exchange sensitive information and services

The approach: establish trust by verifying properties of the other party

Trust negotiation: the approach

Interactions between strangers in open systems are different from traditional access control models

Policies and mechanisms developed in conventional systems need to be revised

USER ID’s

VS.

SUBJECT PROPERTIES

ACCESS CONTROL POLICIES

VS.

DISCLOSURE POLICIES

Subject properties: digital credentials

Assertion about the credential owner issued and certified by a Certification Authority.

CA

CA

CA

CA

Each entity has an associated set of credentials, describing properties and attributes of the owner.

Use of Credentials

Credential

Issuer

Digital Credentials

-Julie

-3 kids

-Married

-American

Company A

Company B

Want to know citizenship

Want to know marital status

-Julie

- American

-Julie

- Married

Alice

Check Check

Referenced from http://www.credentica.com/technology/overview.pdf

Credentials

Credentials can be expressed through the Security Assertion Mark-up Language (SAML)

SAML allows a party to express security statements about a given subject

- Authentication statements

- Attribute statements

- Authorization decision statements

Disclosure policies Disclosure policies govern:

Access to protected resources

Access to sensitive information

Disclosure of sensitive credentials

Disclosure policies express trust requirements by means of credential combinations that must be disclosed to obtain authorization

Disclosure policies

Disclosure policies - Example

Suppose NBG Bank offers loans to students To check the eligibility of the requester, the Bank asks the

student to present the following credentials

- The student card

- The ID card

- Social Security Card

- Financial information – either a copy of the Federal Income Tax Return or a bank statement

Disclosure policies - Example

p1= ({}, Student_Loan Student_Card());

p2= ({p1}), Student_Loan Social_Security_Card());

p3= ({p2}, Student_Loan Federal_Income_Tax_Return());

p4= ({p2}, Student_Loan Bank_Statement());

P5=({p3,p4}, Student_Loan DELIV);

These policies result in two distinct “policy chains” that lead to disclosure

[p1, p2, p3, p5] [p1, p2, p4, p5]

Trust Negotiation - definition

The gradual disclosure of credentials and requests for credentials between two strangers, with the goal of establishing sufficient trust so that the parties can exchange sensitive information and/or resources

Trust-X system: Joint Research with University of Milan

A comprehensive XML based framework for trust negotiations:

Trust negotiation language (X-TNL)

System architecture

Algorithms and strategies to carry out the negotiation process

Trust-X language: X-TNL

Able to handle mutliple and heterogeneus certificate specifications:

Credentials Declarations

Able to help the user in customizing the management of his/her own certificates

X-Profile Data Set

Able to define a wide range of protection requirements by means of disclosure policies

X-TNL: Credential type system

X-TNL simplifies the task of credential specification by using a set of templates called credential types

Uniqueness is ensured by use of XML Namespaces

Credential types are defined by using Document Type Definition

<!DOCTYPE library_badge[ <!ELEMENT library_badge (name, address, phone_number*, email?, release_date, profession,Issuer)><!ELEMENT name (fname, lname)><!ELEMENT address (#PCDATA)><!ELEMENT phone_number (#PCDATA)><!ELEMENT email (#PCDATA)><!ELEMENT release_date (#PCDATA)><!ELEMENT profession (#PCDATA)><!ELEMENT fname (#PCDATA)><!ELEMENT lname (#PCDATA)><!ELEMENT Issuer ANY><!ATTLIST Issuer XML:LINK CDATA #FIXED “SIMPLE” HREF CDATA #REQUIRED TITLE CDATA #IMPLIED><!ATTLIST library_badge CredID ID #REQUIRED><!ATTLIST library_badge SENS CDATA #REQUIRED>]>

Trust-X negotiation phases- basic model

1. Introduction

Send a request for a resource/service Introductory policy exchanges

2. Policy evaluation phase

Disclosure policy exchange Evaluation of the exchanged policies in order to determine

secure solutions for both the parties.

3. Certificate exchange phase

Exchange of the sequence of certificates determined at step n. 2.

Trust-X Architecture

C O N T R O L L E RR E Q U E S T E R

X -P R O FILE

C O M P L I AN C E C HE C KE R

PO L I C YB A SE

X -P R O FILE

C O M P L I AN C E C HE C KE R

T R E EM A N A G E R

T R E EM A N A G E R

P O L I C Y E X C H A N G E

PO L I C YB A SE

Trust-X has been specifically designed for a peer-to-peer environment in that each party is equipped with the same functional modules and thus it can alternatively act as a requester or resource controller during different negotiations.

Upon receiving a disclosure policy the compliance checker determines if it can be satisfied by any certificate of the local X-profile.

How a policy is processed

COMPLIANCE CHECKER

TREEMANAGER

Policy Base Policy ReplyX-Profile

Disclosure Policies

Then, the module checks in the policy base the protection needs associated with the certificates, if any. The state of the negotiation is anyway updated by the tree manager, which records whether new policies and credentials have been involved or not.

Semantic Web

http://www.cs.washington.edu/homes/pedrod/papers/iswc03.pdf

http://www4.wiwiss.fu-berlin.de/bizer/SWTSGuide/

- Web page on some of the papers related to semantic web, security and trust

- W3C recommendations for privacy, security, trust. Brian Matthews, W3C UK Office at RAL, March 2002. - Short presentation about current W3C activities.

Directions

Policies are of much interest to many organizations and applications

- Financial, Medical, Retail, Manufacturing etc Roles and responsibilities Flexible policies RBAC, UCON, RBUC, Trust Negotiation, Dissemination

Policies Need to Know to Need to Share Semantic Web plays a major role