Participatory Sensing through Social Networks

The tension between Participation and Privacy

ITWDC6-8 September, 2010

I. Krontiris,

Chair of Mobile Business

Goethe University Frankfurt

ioannis.krontiris@m-chair.net

F.C. Freiling,

Lehrstuhl Praktische Informatik I

University of Mannheim

Paper outline

What are the benefits and drawbacks of connecting social network

with participatory sensing? 

We study this relation in 2 dimensions that conflict with each other:

 Social translucence (visibility) and Privacy

Goal: Identify and discuss research challenges that arise in this new

setting.

Available Sensors Today

Light sensor

Proximity sensor

Orientation sensor

Microphone

Camera

GPS

Available Sensors Tomorrow

3-axis accelerometer

Proximity sensor

Digital compass

Pollution/air quality sensor

GSR “emotion sensor”

RFID/NFC

Microphone

Camera

GPS

External Sensors

NoiseTube

Architecture Overview

Research Questions

Share – How will collected data be shared? What practices of

individual ownership will be appropriate and how will privacy be

addressed? How can data best be shared with non-experts, urban

planers, decision and policy makers, etc.?

Change – What tools or frameworks best invite and encourage active

participation? What tools and techniques will facilitate the most

productive debate and ultimate positive social benefit?

Utilizing Social Networks

Benefit 1: Recruitment (getting people to join)

identify and reach well-suited participants for data collections based on their geographic availability as well as their interests and habits.

allow existing participants to invite their friends to join a group, or see what their friends are doing (which group they joined, in which groups they are most active), etc.

Utilizing Social Networks

Benefit 2: Participation (getting people to participate)

No direct benefits for participants. Why should those who can produce the sensing data take the time to engage in such interactions? Why should they wish to?

Sense of Community

1. Sense of efficacy: a sense that they have had some effect on the group.

Utilizing Social Networks

2. Recognition Reputation Points

a user, after submitting a report from his mobile phone, is given a reputation point.

reputation points are public and appear on the public profile of that user.

Utilizing Social Networks

Benefit 3: Acting on the data Not all data are equally useful / important People could also intentionally submit fault data

Pre-evaluation by the users

Example: A system that allows users to submit images of potholes on the street

location privacy

Privacy vs. Visibility

Anonymity Social Translucence

Knowing when a particular person was at a particular point in time can be used to infer a lot of personal information

Allow users to make their contributions visible to the online community

Research question

System model: Users submitting data are anonymous, but at the same

time they maintain a public profile in the social network, where they

provide details about themselves (e.g. reputation, etc.)

Is it possible to offer anonymity to the user, who submits sensing data

from the physical environment, while at the same time we maintain

properties connected with his public profile, like

Reputation and

User revocation?

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Anonymity

Let’s assume we provide anonymity to protect user’s privacy

Data are anonymized

Hide network identifiers

Reputation

Giving reputation points to an anonymous user is not possible

Need two independent processes:

A pseudonymous user acquires reputation points (one-time pseudonym)

A known user updates its reputation in his public profile

Solution direction: Use e-cash systems

A pseudonymous user obtains e-coins from the bank for a report

submission, which corresponds to a reputation point

At a later point in time, the user logs-in using his public profile and

redeems the e-coin to increase his reputation.

Hard: Repetitions of this process should not be linkable!

User revocation

Before submit, user authenticates anonymously to the service provider

This encourages user misbehavior need for user revocation

Revocation depends on anonymous authentication mechanism: If use group signatures: A Trusted-Third-Party manages user accounts and has the

ability to revoke user’s anonymity at any time. No assurances that TTP is reliable!

If use e-cash: Anonymity is revoked if spent an e-coin twice

If use k-Times Anonymous Authentication: Anonymity is revoked if user authenticates

more than k times.

None of this appropriate. Need a d-strikes-out revocation system

When users are judged to have misbehaved d times, they are revoked by the system

Some protocols exist, but very expensive for power-limited mobile phones

Conclusions

Utilization of social networks could provide many benefits in urban sensing recruit more citizens in campaigns and boost their active

participation. Example: use of reputation systems

It is also important to preserve the anonymity of the users submitting data Anonymity makes it hard to revoke misbehaving users or compute

their accumulated reputation points

Acknowledgment: Thanks to Nicolas Maisonneuve for the inspiring conversations