Social Networks For Dummies Or some clues about Distributed Knowledge Base with Privacy

1. Serge Abiteboul, Alban Galland and a bunch of different people Webdam, INRIA Saclay-Ile-de-France Social Networks For DummiesOr some clues about Distributed Knowledge Base with Privacy

2. Summary • Introduction • Definitions • Goal • Related works • Distributed Knowledge Base with Privacy • Ask-owner implementation • Indexed-DHT implementation • Friendly-Gossip Implementation • Declarative Expression of Privacy • Social Knowledge Mining • Demonstration • Conclusion

3. My definition of Social Network • Social Network: a (web) application where users store and consult data and interact with data of other users following explicit relationships • Some important notions • Users : people • Data : graph of XML documents, AXML • Data-management : storage, replication, query • Relationship

4. My definition of Privacy • Privacy: the fact that a user keeps control over her data and activity • Some important notions • Read and write permissions • Delegation of permissions • (Anonymity of activity) • (Anonymity of aggregated data)

5. Goal • Define and implement the basis for a distributed social network that guarantees access control • More precisely • Distributed knowledge base with access control • Declarative high level access control specification • Also • Social network application • Social knowledge mining

6. Related works • Social network • Some typically centralized SN systems with limited access control management • Some SN-specific applications • Some works on knowledge mining in SN • Distribution • Distributed Hash Table and indexing (KadoP) • Friend based P2P • Privacy • Access control and logic • Cryptography

7. Distributed Knowledge Base with Privacy • Access control lists at the principal level • A principal corresponds to a set of access rights and documents – e.g., a user or a group • Rights : read (query), append, write (delete), own (grant, revoke) • Some languages (logics) to speak about cryptography and communications • Signature, encryption • Time • Messages

8. Distributed Knowledge Base with Privacy • One can consider different architectures/ implementations • We focus on (1+) 3 • (Centralized system) • Ask-owner implementation • Indexed-DHT implementation • Friendly-Gossip implementation

9. Ask-owner implementation • Basic semantic Ownership Signed Instructions Results

10. Indexed-DHT implementation 2 1 Index Ownership 1 Signed Instructions Encrypted Results Access Access

11. Indexed-DHT implementation • Principals are no more physically hosted by one machine but data are distributed as posts on a P2P system with a DHT • Each post is signed and encrypted. Hosts : • Understand some meta-data • Do not understand the content they store • Three key kinds of posts : update (write or append), access and index

12. Indexed-DHT implementation • Update posts • q says (doc@q, tapply , T, C for q) where : • q : principal id • doc : document id • tapply : update timestamp • T : write or append • C for q : content encrypted by a reader public key • Write/Append right = signature private key • A host can easily check it get a valid post 1 1

13. Indexed-DHT implementation • Update posts • Read right = reader private key • A reader can check she gets a valid version, or otherwise ask another host • In the general case, hosts exchange signatures on list of posts • If you forget about append, replication can be replaced by time of validity and refresh 1 1

14. Indexed-DHT implementation • Access posts • q says tapply,(key for u), (u,R for q) where : • q : principal id • u : another principal • key : cryptographic key (explicit delegation) • R : access right (read, write, append, own) • Revocation : add time to post + full (or lazy) regeneration of dirty keys Access

15. Indexed-DHT implementation • Index posts • Balance between leak of information and efficiency of queries • May need more meta-data, like an encryption schema • Could be managed as regular update Index

16. Indexed-DHT implementation • Other versions depending of • Hierarchy of rights • Who can access the list of access controls of a principal • Some reasons to use a logic language for access control • Need a clear way to express the exchange of knowledge • Need to make some proof

17. Friendly-Gossip Implementation Ownership Signed Instructions Encrypted Results

18. Declarative Expression of Privacy • Example • People who are tagged on one of my photos can see this photo • People who are friends of two of my friends can read my Wall • People who are best friends of mine can write on my Wall • Problems • Uncontrolled deduction • Fix-point semantic

19. Social Knowledge Mining • Previous works • Recommendation: previous works at Yahoo! Research with Sihem Amer-Yahia • Corroboration (with Serge, Amelie and Pierre S.) • What remains in a distributed system with access control? • Introducing higher level of semantic (belief…)

20. Demonstration • Some functionalities already implemented during Marilena Oita internship • A user interface and global logic • Some part of Distributed Knowledge Base with Privacy • Declarative Privacy is missing

21. Conclusion • This is work in progress • We are currently focusing on distributed knowledge base with access control, wondering if there is any link with knowledge management • Hidden behind trendy Social Networks, we believe there are real topics of research, in particular in distributed systems