what can a click really reveal? the utility and privacy ... · conclusion • we precisely measure...

What Can a Click Really Reveal? The Utility and Privacy Effects of a Click

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Rachid Guerraoui Anne-Marie Kermarrec

Mahsa Taziki

What happens when you access online services?

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Clicks

Recommendations

Utility

Privacy

Trade-off?Always

Outline• Quantifying the utility and privacy effects of a click

- How to measure utility? - How to measure privacy? - How utility and privacy are connected?

• The Click-advisor diagram

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Outline• Quantifying the utility and privacy effects of a click

- How to measure utility? - How to measure privacy? - How utility and privacy are connected?

• The Click-advisor diagram

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How to measure utility?

• A commonality-based utility measure (Commonality of a user profile)

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Utility of a click

Commonality

=

- +

Commonality - Example

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Commonality = 0

Commonality = 0.375

Commonality in Perspective

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Outline• Quantifying the utility and privacy effects of a click

- How to measure utility? - How to measure privacy? - How utility and privacy are connected?

• The Click-advisor diagram

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Disclosure risk of a click

How to measure privacy?

• An entropy-based privacy measure (Disclosure degree of a user profile)

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Disclosure Degree

=

- +

Disclosure Degree - Example

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Commonality = 0

Commonality = 0.375 = 0.9

= 1.2

Disclosure Degree in Perspective

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Outline• Quantifying the utility and privacy effects of a click

- How to measure utility? - How to measure privacy? - How utility and privacy are connected?

• The Click-advisor diagram

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• Clicks that induce a trade-off between utility and privacy: 78.40 %

• Clicks that improve both utility and privacy: 5.12 %

• Clicks that improves neither utility nor privacy: 16.48 %

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How utility and privacy are connected?

Example: Movielens 100K dataset

Different Effects of Clicks

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Outline• Quantifying the utility and privacy effects of a click

- How to measure utility? - How to measure privacy? - How utility and privacy are connected?

• The Click-advisor diagram

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Outline• Quantifying the utility and privacy effects of a click

- How to measure utility? - How to measure privacy? - How utility and privacy are connected?

• The Click-advisor diagram - The zone of a click

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The Zone of a Click

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Safe

Deleterious

Dangerous

Trade-off

Trade-off

Outline• Quantifying the utility and privacy effects of a click

- How to measure utility? - How to measure privacy? - How utility and privacy are connected?

• Click-advisor diagram - The zone of a click - The click-advisor diagram

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Recommendations

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Toy Story

Greenberg

The Switch

Pre-clicks

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Toy Story

Greenberg

The Switch

The Click-advisor Diagram

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TToy Story

Greenberg

The Switch

Outline• Quantifying the utility and privacy effects of a click

- How to measure utility? - How to measure privacy? - How utility and privacy are connected?

• Click-advisor diagram - The zone of a click - The click-advisor diagram - The user actions

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The User Actions

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TToy Story

Greenberg

The Switch

You like “Toy Story”. This click is in a safe zone. So, it improves both utility and privacy for you. Do you want to:

Outline• Quantifying the utility and privacy effects of a click

- How to measure utility? - How to measure privacy? - How utility and privacy are connected?

• Click-advisor diagram - The zone of a click - The click-advisor diagram - The user actions - The clicking game

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The Clicking Game

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The Clicking Game

• Reward function

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The Clicking Game

• Reward function

• Users actions

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Confirm / Change / Cancel

The Clicking Game

• Reward function

• User actions

• Clicking strategies

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Clicking Strategies

• Basic: confirms all the pre-clicks.

• Careful: confirms the safe and trade-off pre-clicks; otherwise, cancels.

• Smart: confirms the safe and trade-off pre-clicks;

cancels the deleterious pre-clicks;

changes the dangerous pre-clicks.

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Clicking Game (1)

All users playing smart is a Nash equilibrium, i.e., playing the smart strategy maximizes the reward function for a user u, if every user other than u plays smart.

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Clicking Game (2)

The overall average of the recommender utility for all users playing the smart strategy is the same as the case where users click on items based on their real preferences. However, with regard to privacy, the smart strategy provides better privacy compared to the basic strategy.

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Conclusion

• We precisely measure the utility and privacy effects of a click.

• We show that there is not always a trade-off between utility and privacy.

• The click-advisor diagram makes users aware of the utility and privacy effects of their clicks.

• Consulting the click-advisor, the users can adopt a clicking strategy to improve their privacy without decreasing the overall recommender utility.

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