Social Networks For Dummies

1

Social Networks For Dummies

Or some clues about Distributed Knowledge Base with Privacy

Serge Abiteboul,
Alban Galland
and a bunch of different people

Webdam, INRIA Saclay
-
Ile
-
de
-
France

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


Signed Instructions

Results

Ownership

10

Indexed
-
DHT implementation

Signed Instructions

Encrypted Results

Ownership

1

1

2

Access

Access

Index

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, t
apply

, T, C for q) where :

•
q : principal id

•
doc : document id

•
t
apply

: 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 t
apply
,(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

Signed Instructions

Encrypted Results

Ownership

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