Annual workshop february 5th 2014
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Annual Workshop February 5th, 2014. A Formal Approach to Analyze Privacy in Electronic Services. MSEC Koen Decroix. Outline. Introducing Privacy in Loyalty Services Conceptual model of inShopnito Framework for Formal Reasoning on Privacy Privacy Analysis of inShopnito Conclusions.

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Annual Workshop February 5th, 2014

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Annual Workshop

February 5th, 2014

A Formal Approach to Analyze Privacy in Electronic Services


Koen Decroix

[Koen Decroix – MSEC - KU Leuven]


  • Introducing Privacy in Loyalty Services

  • Conceptual model of inShopnito

  • Framework for Formal Reasoning on Privacy

  • Privacy Analysis of inShopnito

  • Conclusions

Introducing Privacy in Loyalty Systems

Ever wondered what companies know about you?

… Max Schrems, an Austrian student, did!

Now he sues Facebook for their data practices on the personal data they collected about him.

Once, there were small local family-run stores binding customers with …

… with the years, they were replaced by big chains also binding customers …

For the convenience of their customers, loyalty services evolved to electronic services integrated with other online (third-party) services. Is this the full story?

Share your shopping activities with friends on Facebook


Not transparent to users

When registering to such services, you agreed with their terms and policies and gave them your consentfor collecting, processing, and forwarding your personal data.

Your past online activities leave non-erasable, possibly harmful, traces behind and might get spread around.

Citizens must be protected for these data practices.

This is where the European data protection legislation comes into play.

… designers have to consider multiple types of requirements


Need for formal modeling, as a support during design of composite services.

Privacy analysis is based on user profiles built from the formal models. Its feedback must be useful for system designers and users as well.

Conceptual Model of inShopnito

Collecting loyalty points at first glance.

… but looking into more detail …

From specifications of service providers’ data practices (= service policies), we can derive that …

Conceptual model of inShopnito

Framework for Formal Reasoning on Privacy

System Independent Model





Inference Rules

User Model

System Model

Trust Perception



Logic Component


Initial State

Service Policies

Input Model




Access Control

Identifiability Model





Privacy Analysis of inShopnito

Privacy Analysis - Feedback






inShopnito modeled for two user types

Advertisers are not trusted

  • Trusts

  • Grocery Store

  • Loyalty Program Provider

  • inShopnito

No trust in organizations

Loyalty credential: Idemix what if X509 is used?

Linkabilities in inShopnito

Detect Violations in inShopnito

Advertisers not allowed to have the customer’s his:



eMail address

Violations of rules 1, 2, 3 are found only in case a X509 certificate is used in case of the user model


  • It is a formal approach to analyze privacy  power to prove properties

  • Approach is useful during service design

    • privacy by design is one of the principles in EU reform of data protection legislation.

    • analyzing linkabilities, collaborations, attributes in user profiles.

    • verify compliance with legislative and corporate level rules (detecting violations).

  • Approach is useful for education of people

    • EU reform of data protection  authorities get the task to educate people. E.g., model a user that participates to a survey about Facebook. Afterwards, perform a privacy analysis based on his assumptions and present him the difference between what he thinks and what can happen.


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