Towards Accountable Management of Identity and Privacy: Sticky Policies and Enforceable Tracing Services Marco Casassa Mont Siani Pearson Pete Bramhall

Towards Accountable Management of

Identity and Privacy: Sticky Policies and Enforceable Tracing

ServicesMarco Casassa Mont Siani PearsonPete Bramhall

Trusted Systems LaboratoryHewlett-Packard Labs, Bristol, UK

TrustBus 2003, 2-4 September 2003

Prague, Czech Republic

page 210/06/06 Trusted Systems Laboratory – Hewlett-Packard Labs, Bristol - UK يح

Presentation Outline

• Setting the Context• Scenario• Addressed Problems• Related Work• Our Approach• Discussion• Conclusions


Setting the Context

• Digital Identities and Profiles are relevant to enable transactions and interactions on the web, in many contexts: personal, social, business, government, etc.

• Privacy Management is a major issue: involves people, organisations, governments, etc.

• Different reactions by people: ranging from “completely ignoring the privacy issues” to “being so concerned to prevent any web interaction”


Scenario: Multiparty Interactions [1]

User

Enterprise Enterprise

Negotiation ofPrivacy Policy

Provision ofIdentity & Profile

Data

Identity/Profile

Disclosure

Multiparty Transaction / Interaction

Policies Enterprise

Data

Services

Services

Services

Similar issues in the e-Commerce, Enterprise, Financial and Government Areas


Scenario: Multiparty Interactions [2]

• Little has been done so far to directly involve people (or third parties acting on their behalf) in the management of their privacy

• Users lack control over their personal information after their initial disclosures

• Organisations, as well, lack control over the confidential information they manage on behalf of their customers, once they disclose it to third parties

• It is hard to make organisations accountable


Addressed Problems

• Privacy Enforcement

• Accountability of Organizations

• Involvement of People in the Management of their Personal Data


Related Work [1]

• Lot of work done to provide Legislative Frameworks for Privacy

• Different legislative approaches: example US vs. EU

• Privacy and Data Protection laws are hard to enforce when personal information spreads across boundaries

• In general users have little understanding or knowledge of privacy laws and their implications


Related Work [2]

• W3C approach on Platform for Privacy Preferences (P3P): simple policies, point-to-point interactions. Little control on the fulfilment of these policies (at least, in the current implementations)

• Liberty Alliance and Microsoft Passport: Identity and Privacy Management based on closed web of trust and predefined policies


Related Work [3]

• IBM’s work on Enterprise Privacy Authorization Language (EPAL) and related Privacy Framework

• Association of fine-grained Privacy Policies (Sticky Policies) to personal data. Enforcement of Privacy Polices by the Enterprise • Current Open Issues:

- Policy “Stickiness” is not enforceable; - Too much trust in the enterprise; - Leakages of personal data can still happen; - Little user’s involvement.

• The above issues are very hard to address!

page 10

10/06/06 Trusted Systems Laboratory – Hewlett-Packard Labs, Bristol - UK يح

Our Approach

About a Privacy and Accountability Model encompassing:

• “Sticky” Privacy Policies strongly associated to Identity Information

• Mechanisms for strong (but not impregnable) enforcement of privacy policies

• Mechanisms to increase the Accountability of the involved parties

• Mechanisms to allow people to be more involved in the management of their data (if they want to …)

page 11


Privacy and Accountability Model

Key aspects: • Confidentiality of Data: obfuscation of confidential data

• Strong Association of Privacy Policies to Confidential Data: - “tamper resistant” policies associated to data.

- “Stickiness” guaranteed at least till the first disclosure.

• Policy Compliance Check and Enforcement: by trusted Tracing & Auditing Authorities (TAAs) and Trusted Platforms + OSs

• Accountability Management: auditing and tracing of disclosures by TAA (used as evidence)

• User Involvement: policy authoring, notification, authorization

page 12


Privacy and Accountability Model [1]

Tracing and Auditing Authorities (TAAs)

? ?

6

User Enterprise

Multiparty Transaction / Interaction

Policies

Enterprise

Data

Services

Services

Services

Enterprise

Negotiation ofPrivacy Policy1

Obfuscated Data+

Sticky PrivacyPolicies

StickyPolicies

2

Request for Disclosure of Data+

Sticky Privacy Policies+

Credentials

3Checking forIntegrity and

Trustworthiness ofRemote Environment

4

Request for Authorizationor

Notification

5

Decryption Key(if Authorised)

6

7

Obfuscated Data+

Sticky PrivacyPolicies

8

page 13


Privacy and Accountability Model [2]

• Once confidential data is disclosed it can still be misused …• Risks Mitigation via:

• Audit trail: Audit logs managed by TAAs can be used as Evidence and for Forensic Analysis (logging at least the first disclosure …)

• Trusted Platforms and OSs: - checking for the Integrity of the Receivers’ environment - enforcing part of the Privacy Policies directly at the OS level. Research and Work in Progress …

page 14


Privacy and Accountability Model: Technical Aspects [1]

• Identifier-based Encryption (IBE)

• Trusted Platforms (TCG was TCPA, etc.)

• Tagged Operating Systems (OSs)

A technical implementation of our Privacy and Accountability Model leverages three key technologies:

page 15


What is Identifier-based Encryption (IBE)?

• It is an Emerging Cryptography Technology

• Based on a Three-Player Model: Sender, Receiver, Trust Authority (Trusted Third Party)

• Same Strength of RSA

• Different Approaches: Quadratic Residuosity, Weil Pairing, Tate Pairing …

• SW Library and Technology available at HP Laboratories

page 16


IBE Core Properties

• 1st Property: any kind of “string” (or Sequence of Bytes) can be used as an IBE Encryption Key: for example a Role, an e-Mail Address, a Picture, a Disclosure Time, Terms and Conditions,

a Privacy Policy …

• 2nd Property: the generation of IBE Decryption Keys can be postponed in time, even long time after the generation of the correspondent IBE Encryption Key

• 3rd Property: reliance on at least a Trust Authority (Trusted Third Party) for the generation of IBE Decryption Key

page 17


IBE Three-Player Model

AliceAlice

Trust Authority

Trust Authority

BobBob

3. Alice chooses an appropriate Encryption

Key. She encrypts the message:

Encrypted message

= {E(msg, N, encryption key)}

32. Alice knows the Trust Authority's published value of Public Detail N It is well known or available from reliable source

2

1. Trust Authority - Generates and protects a Secret - Publishes a Public Detail N

1

4. Alice Sends the encrypted Message to Bob, along with the Encryption Key

4

5. Bob requests the Decryption Key associated to the Encryption Key to the relevant Trust Authority.

5

6. The Trust Authority issues an IBE Decryption Key corresponding to the supplied Encryption Key only if it is happy with Bob’s entitlement to the Decryption Key. It needs the Secret to perform the computation.

6

page 18



A technical implementation of our Privacy and Accountability Model leverages three key Technologies:




page 19


Trusted Platforms

• A trusted platform provides hardware mechanisms (TPM) and tools to check for the integrity of computer platforms and their installed software (locally and remotely)

• TCG (was TCPA) and Microsoft NGSCB initiatives: http://www.trustedcomputing.org

http://www.microsoft.com/ngscb • HP and HP Laboratories are directly involved in the TCG

initiative

TPM

http://www.trustedcomputing.org/



http://www.microsoft.com/ngscb




page 20



A technical implementation of our Privacy and Accountability Model leverages three key Technologies:




page 21


Policy Creation and Translation System

policies created in dflow

compiler

Policy evaluati

on engine

Tagged Data

Flow causing

operationyes, no, more checks

Decision

Control Enforcement

Policy

File in

Internal

Format

• A tagged Operating System (OS) provides mechanisms and tools to associate low level labels to data and directly enforce and manage them at the OS level.

• The “stickiness” of a label to the content, not to the content holder (such as a file), ensures that even when the data is copied around the label follows it as well.

• Labels can be associated (at the OS level) to low level Privacy Policies (rules), directly enforced by the OS. Rules dictate constraints on: copies of data, data transmissions, etc.

• A working prototype is available at HP Laboratories, Bristol.

Tagged Operating Systems

page 22



- (High level) Stickiness of Privacy Policies - User Involvement- Accountability Management- Enforcement of Aspects of Privacy Policy

Addressed Problems

- (Low level) Source of Trust and HW/SW integrity checking

- (Low level) Stickiness of Privacy Policies - Enforcement of Aspects of Privacy Policy

Technologies

Trusted Platforms (TCG …)

Tagged OSs

Our Privacy and Accountability Framework

(IBE, TAAs, etc.)

GAP

GAP

page 23


High-level System Architecture

LocalIdentity and ProfileInformation

Browser

Plug-in

Comm.Module

Policy Engine

IBE CryptoModule

CredentialDatabase

IBECryptoModule

Tamper Resistant Storage

Tracing Auditing Module

User siteReceiver Site(s)

Trust Authority(s)[Tracing and Auditing Authorities]

Obfuscated Data Package +

Sticky Privacy Policies

IBE DecryptionKey

Request for IBE Decryption Key:<Disclosure Policies (Sticky Privacy Policies) and credentials>

Notifications andAuthorizations

1

24 3

Disclosure Monitoring/Control

Disclosure Monitoring/Control

Disclosure Monitoring/Control Customers

Database

service

Comm. Module

Policy Engine

Tagged OS + TPM

Tagged OS + TPM

PolicyDeployment

PolicyDeployment

• Based on the IBE Model

• Privacy Policies are represented as “IBE Encryption Keys”

• Confidential data is encrypted with IBE encryption keys

• IBE encryption keys “stick” with the encrypted data (at least till the first de-obfuscation of the data …)

• The “Tracing and Auditing Authority” is an (IBE based) Trust Authority.

• Leveraging Trusted Platforms and Tagged OS for enforcing aspects of Privacy Policies (Work in Progress…)

page 24


Sticky Privacy Policies

Example of high-level Sticky Policy (XML format):<sticky policy> // disclosure policy – IBE encryption key <attribute> name of the identity or profile attribute </attribute> <Trust Authority> address and location of the Trust Authority </Trust Authority> <owner> //reference name – IBE encryption key <reference name> pseudonym1 </reference name> //encrypted call back address by using user’s reference name <owner’s details> encrypted call back address <owner’s details> </owner> <validity> expiration date </validity> <constraint> X.509_authentication_required </constraint> <constraint> allow_sharing_of_data </constraint> <constraint> // Simple constraint on remote platform required_remote_TCG_trusted_platform </constraint> <action> notify_owner </action> </sticky policy>

Reference to TA(s)

Constraints/Obligations

Platform Constraint

Actions(User Involvement)

IBE encryption keys can define any kind of privacy constraints or terms and conditions tobe deployed and enforced at different levels of abstractions (application/service, OS, platform)

page 25


Enforcement of Sticky Privacy Policies

TCGTagged OS

TCG

Trust Authority (TA)

TCGTagged OS

TCG

TCGTagged OS

TCG

Enterprise 1

Enterprise 2

Policy Engine

Enforcement viaTrust Authority

Enforcement By Trusted Platforms andTagged OS(Work in Progress)

Personal Data

Sticky

Privacy Policies

Policy Engine

Policy Engine+

page 26


Policy Enforcement by Trust Authority

• “Soft” policy enforcement: TA still relies on the receiver to take care of the data privacy, once data is disclosed …

• The TA interprets Privacy Policies via a Policy Engine

• The TA makes sure that the Privacy Policies are satisfied before issuing the IBE decryption key

• Multiple TAs can be used, each of them specialised in doing specific checks (easy with IBE-based approach …)

• Users can be notified or asked for authorization, if the Privacy Policies require it (User Involvement)

• Audit of disclosures, at least the first time …

•The TA can leverage TCG and Tagged-OS to make sure that part of the policy enforcement is done upfront …

Enterprise 2

Enterprise 1

Trust Authority (TA)

Privacy

Policies Privacy

Policies

page 27


Policy Enforcement by Trusted Platforms

• Stronger Enforcement of part of the privacy policies (low level policies)

• TCG integrity checking mechanisms checks for platform trustworthiness along with its SW and HW integrity. Cross boundaries integrity checking on the platforms of the involved parties

• To be effective, a widespread usage of trusted platforms is required. At least all the platforms involved in the task of processing confidential data should be checked. Some of them might not be exposed externally. Too strong requirements for the time being … Limits on the kinds of HW and SW checks …

• Joint usage of Tagged-OS and TCG to create Trust Domains. TCG to check upfront the integrity of the “combined” system. Tagged-OS to enforce privacy policies directly at the OS level: disallow copies data, sending data only to specific IP addresses, etc.

Enterprise 2

Tagged OS

TCGTagged OS

TCG

Enterprise 1

Trust Authority (TAA)

Tagged OS

TCGTagged OS

TCG

Tagged OS

TCGTagged OS

TCG

Privacy

Policies

Research and Work in Progress …

Trust Domain

page 28


Accountability Management

• Confidential data is encrypted: at least the first time the requestors need to interact with the Tracing and Auditing Authorities (TAAs)

• Auditing and Logging of data disclosures carried on by TAAs (at least the first time)

• Multiple TAAs can be used to mitigate trust issues. Users can run their own TAAs

• Usage of Audit Logs as Evidence and for Forensic Analysis

• Research in progress at HP Labs on tamper-resistant audit systems

Enterprise 2

Enterprise 1

Trust Authorities (TAAs)

Privacy

Policies

Privacy

Policies

page 29


Discussion

• The usage of “trusted third parties” to mediate interactions and encryption for confidentiality are not new

• The potential added value of our approach consists of: The mechanisms to associate “Sticky” Privacy Policies to confidential data via IBE (lightweight cryptography mechanism); The “active” interaction model we introduced The combined usage of TCG, Tagged OS and Trust Authorities for integrity checking and policy enforcement

• Other cryptography mechanisms could be used but the IBE model fits

very well at the client and server sites

• Open issues: Our policy enforcement is strong, but not impregnable (risks vs. costs?) Adequacy of Trusted Platforms/Tagged OS to be verified Potential complexity of our solution. To be fully prototyped and tested

• Research in progress …

page 30


Current and Future Work

• IBE technology is available. HP Labs have implemented a fast and optimised version of the IBE cryptography libraries

• We have simple implementations of: - a TA service - add-ins for authoring and management of privacy policies - a policy-based engine

• TPM chips and TCG-based PCs are available on the market

• We have a working prototype of the Tagged OS • We have a working prototype of a non-repudiable, tamper resistant Auditing and Logging System.

• Next steps: testing the suitability of our approach in real contexts …

page 31


Conclusions

• It is important to protect people’s privacy on the Internet, increase accountability and allow people to be more involved (if they care)

• Despite laws, legislations and technical attempts to solve this problem, at moment there are no solutions to address the whole set of involved issues

• We described our approach to provide a strong but not impregnable enforcement of privacy policies, more accountability and more user involvement

• We presented a technical solution that leverages IBE (sticky policies and auditing services), Tagged-OS (low level sticky policy) and TCG (trust and integrity checking)

• There are open issues: our research is in progress …

page 32


Backup Slides

RSA and IBE

Cryptography Models

page 33


RSA Model

Secrets p&q

Compute d&eKeep d secret

Compute N = p*q

encrypt

decryptN and d

e and Npublished

page 34


IBE Model [1]

Publicdetails

E D

Encrypt Decrypt

Secrets s

Compute publicdetails Compute

Key pairs

page 35


IBE Model [2]

Publicdetails

Encrypt Decrypt

Secrets s

Compute publicdetails Generate

Decryption Key

Choose eGet decrypt

Key,e

Documents

Towards Accountable Management of Identity and Privacy: Sticky Policies and Enforceable Tracing Services Marco Casassa Mont Siani Pearson Pete Bramhall