1. DECENT: A Decentralized Architecture for Enforcing Privacy in Online Social Networks Sonia Jahid 1, Shirin Nilizadeh 2, Prateek Mittal 1, Nikita Borisov 1, Apu Kapadia 2 1 University of Illinois at Urbana-Champaign 2 Indiana University Bloomington Presented by: Sonia Jahid SESOC, 2012

2. Privacy Issues 2

3. Decentralization - Challenges Availability Access control by others Confidentiality/Integrity Malicious activities 3 Provider Trusted Party Myself Hybrid Untrusted Party Existing Research – Diaspora* [ http://joindiaspora.com ] – LotusNet [Aiello et al. ’12] – SafeBook [Cutillo et al. ’09 ] – PeerSoN [Buchegger et al. ’09] – Persona [Baden et al. ’09] DHT Cryptography

4. 4 Wall Status Comment Video Link OSN Data is complicated

5. Our Contribution Address the challenges – Decentralization of the OSN architecture – Advanced cryptography – Other design philosophes 5

6. Design – Data Structure 6 ObjectDataPolicyReferenceList Status Message Friend or Family Alice|Friend & Family Object Like! Friend or Colleague|Bob|Friend CommentReference Alice’s Status Bob’s Comment Read Write/Delete Append ID, Read-Policy, Write-Policy

7. Design – Privacy Policy Restrictive Policy on comments 7 Status DECENT rocks!Friend and FamilyCommentReference Alice Comment Like! Colleague or Neighbor BobAlice StatusReference 1

8. Design - DHT Provides – Storage/Lookup Operation – Availability – Append Operation Verifies – Write policy – Append policy Can not – Relate data to its owner – Figure out data owner’s social graph 8

9. Design – Confidentiality and Integrity Attribute-based Encryption – User-defined attribute-based policy – Frequent revocation 9 Bob CarolDiana 1 AND Colleague Neighbor OR Friend friend, neighbor colleague friend, colleague Alice S.Jahid, P.Mittal, N.Borisov, EASiER: Encryption-based Access Control in Social Networks with Efficient Revocation

10. Data Design – Confidentiality and Integrity Integrity Write Policy – set to the owner – Request signed with Write-Secret-Key – Verified by readers Append Policy – attribute-based – Comment-reference signed with Append-Secret-Key – Verified by readers Confidentiality ABE 10 Write-Public-Key Append-Public-Key E Alice (Write-Secret-Key) Alice’s Object ABE(Append-Secret-Key) Sign ABE Sign(CommentRef 1 ) Sign (CommentRef 2 )

11. Implementation and Evaluation Prototype in Java Simulation - FreePastry Simulator Experiments on PlanetLab – Kademlia 11 Simulation (60 Statuses) Experiment on PlanetLab (12 Statuses) Cryptography Progressive Lookup

12. Conclusion Contribution – Design and prototype of a decentralized OSN – Preliminary performance results Ongoing Work – Optimizations in cryptography and DHT Lookup 12 Shirin Nilizadeh Prateek MittalApu Kapadia Nikita Borisov

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