whatsup: a p2p instant news item recommender · • classical notification systems do not filter...
TRANSCRIPT
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WhatsUp: a P2P instant news item recommender Anne-Marie Kermarrec INRIA Rennes
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The new deal
User centric: Web content is generated by you, me, your
friends and millions of others
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Social networking in a 2 billion user world
1 billion accounts (Oct 2010)
20M unique/month
200M registered
10M (Oct 2011)
50M registered (Oct 2011)
6M unique/month
900M (Spring 2012)
15M registered 140,000 contributors on 30 days
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The new deal
A user-centric Web
A small world: everybody sits close to everybody else
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The new deal
User-centric
Small world
Navigation shift: Notification is taking over
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Notification is taking over
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The new deal
User-centric
Small world
Navigation shift
Personalization around the corner:
recommendation, RSS feeds, social
networks, … Communications of the ACM June 2011
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A personalized environment
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We are not there yet
Amazon recommends me a fryer
Some of my Facebook friends write in Italian
LeMonde.fr informs me on the Champion’s ligue
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Why is it so difficult?
• Dynamic interests
• Small portion of the available information is of interest
• Interesting stuff does not come always from friends
• Classical notification systems do not filter enough
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What’s wrong with centralized versions?
Privacy: Big Brother is watching you
Scaling issues
If you only knew the power of the Dark Side. – Darth Vader
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ACHIEVING PERSONALIZED NOTIFICATION IN A DECENTRALIZED WAY
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A call for decentralization
User-centric world
Small world
Navigation shift
Personalization
Privacy-aware
Scalable
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WhatsUp: a decentralized recommender
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WhatsUp: a decentralized news item recommender
Simple interface: I like it or I don’t
Create a dynamic implicit social network
Disseminate news along this topology
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WhatsUp in a nutshell
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WhatsUp challenges
Who are my social acquaintances
How to discover them?
How to disseminate news items?
How to preserve users’privacy
Similarity metric
Sampling
Biased epidemic protocol
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Which nodes for the social network?
Model
U(sers) × I(tems) (news items)
Profile(u) = vector of liked news items
Cosine similarity metric
Minimal information: no tag, no user’s input
!"#"$%&"'(! !!! ! ! !!!! ! !
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WhatsUp challenges
Who are my social acquaintances?
How to discover them?
How to disseminate news items ?
How to preserve users’privacy
Through sampling
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Gossip Protocols
Probabilistic approach
Goal: system to converge to a desirable outcome
Trade determinism for scalability & robustness
F. Taiani 22
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Each node maintains a set of neighbors (k entries)
P Q
Data exchange
Data processing
Peer selection
Parameter Space
Gossip-based computing
Random Peer sampling [ACM TOCS 2007] achieves
random topologies
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Random dynamic graph
N I
B
C D E
F
G B C D E
A
F G
C
D
E A
F G
C
N I
(1) peer list exchange (2) merge and truncation
one gossip round
shuf
fle Result ➙ random graph
Highly resilient against churn, partition
Small diameter
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Sampling the network with gossip
Similarity computation
exchange of neighbors lists
neighborhood optimization 1 2
Alice Bob
Carl
Dave Ellie
Frank
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The WhatsUp social network
RPS layer providing random sampling
clustering layer gossip-based topology clustering
Social link Random link
Alice Bob
Carl
Dave
Ellie
Alice Bob
Carl
Dave
Ellie
node
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Data structures
@IP: port 102.14.18.1:2110
Bloom Filter 100100000110
Update time 30
@IP:port 132.154.8.5:2020
Bloom Filter
010111011001
Profile I like it: : N1, N2, … I don’t : N10
, N13, …
Update time
5
Social Network of the c
closest entries
Uniform (dynamic) sample of k
random entries
@IP:port 132.154.8.5:2020
Bloom Filter
010111011001
Profile I like it: : N1, N2, … I don’t : N10
, N13, …
Update time
5
@IP:port 132.154.8.5:2020
Bloom Filter
010111011001
Profile I like it: : N1, N2, … I don’t : N10
, N13, …
Update time
5
@IP:port 132.154.8.5:2020
Bloom Filter
010111011001
Profile I like it: : N1, N2, … I don’t : N10
, N13, …
Update time
5
@IP:port 132.154.8.5:2020
Bloom Filter
010111011001
Profile I like it: : N1, N2, … I don’t : N10
, N13, …
Update time
5
@IP: port 102.14.18.1:2110
Bloom Filter 100100000110
Update time 30
@IP: port 102.14.18.1:2110
Bloom Filter 100100000110
Update time 30
@IP: port 102.14.18.1:2110
Bloom Filter 100100000110
Update time 30
@IP: port 102.14.18.1:2110
Bloom Filter 100100000110
Update time 30
@IP: port 102.14.18.1:2110
Bloom Filter 100100000110
Update time 30
@IP: port 102.14.18.1:2110
Bloom Filter 100100000110
Update time 30
Exchange of Bloom filters
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Convergence
Cycles
c current neighbors versus the c closest
Biased sampling
Random sampling
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WhatsUp challenges
Who are my social acquaintances
How to discover them?
How to disseminate news items ? Biased epidemic protocol (BEEP)
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Epidemic dissemination
The log(n) magic Each node forwards the message to f nodes chosen uniformly at random If f=O(log(n)), “atomic” broadcast whp Result is valid if the fanout for each peer is on average
Fanout: log(n) + c
Random is connected : -c-e e p(connect) =
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BEEP: orientation and amplification
Orientation: to whom?
Forward to friends
Forward to random users
Amplification: to how many?
Increase fanout
Decrease fanout
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I like it: Exploit
Large fanout
F≈ log(N) friends in the social network
Forward to friends
Amplification: to how many?
Orientation: to whom?
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I don’t like it: Explore
Orientation: to whom?
Small fanout
Forward to random users
F= 1 node from the RPS, the closest to the news items profile
Amplification: to how many?
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Beep
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Evaluation
User Metrics: Recall-Precision
System metrics: Number of messages-Redundancy
Traces
• Real trace from a 480 user survey on 1000 news items
• Delicious and Digg crawls
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WhatsUp in action on the survey
Precision Recall Redundancy Messages Gossip
0.34 0.99 0.85 2.3 M
Cosine-CF
0.64 0.12 0.27 30k
Whatsup
0.53 0.78 0.28 280k
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WhatsUp in action
Fanout
0
0.2
0.4
0.6
0.8
1
3 4 5 6 7 8 9 10 11 12
F1
-Sco
re
Fanout
WhatsUpGossip
Cosine based CF
WhatsUp
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WhatsUp challenges
Who are my social acquaintances?
How to discover them?
How to disseminate news items ?
How to preserve users’privacy?
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A wide range
Blurring the profile
Anonymity: Onion-like solutions
Traditional privacy: threshold protocol
Differential privacy: distributed noise
STRONGER GARANTEES
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Blurring the profile
Aggregation of profiles of users who liked
the news item
News item profile
Private User profile
User Profile exchanged
during gossip
Public User profile
User Profile used locally for
similarity computation
I like it
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Impact of profile bluring
Fanout
0
0.2
0.4
0.6
0.8
1
2 4 6 8 10 12 14
F1-S
core
Fanout
Privacy-unaware-WupPrivacy-aware-Wup
Privacy-unaware WhatsUp WhatsUp
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Resilience to attacks
0
0.2
0.4
0.6
0.8
1
0 16 32 48 64 80 96 112 128
Rec
all
Number of Attackers
WhatsUpPrivacy-unaware WhatsUp
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Anonymity (sender and receiver)
Dissociates the profile from the user’s identifier
Additional Private RPS
Relay nodes from the RPS
Three types of keys
• Chain keys (RPS)
• Profile keys (Private RPS)
• Symmetric keys for path anonymity A B
PA PB
Private RPS provides profile keys and proxys
Onion routing: chain of random nodes, keys provided by the RPS
Chain created of random nodes, keys assigned by the nodes
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P
Anonymous Profile exchange
A ProfileA
PA
RA
B
PB
RB
PB PA
RB
B
ProfileA
A encrypts its profile with Profilekey of B (Private RPS) Then with Chainkeys of RA and PA (RPS)
ProfileA
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Profile hiding: threshold protocol
The profile might be enough to identify a user
Threshold
Nothing in common All in common
0.3 0.6 Alice
Bob
Homomorphic encryption
[Golreich 2003] operations performed
(multiplication, scalaring) directly
on cipher-texts.
Only one bit of information revealed
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Differential Privacy
Ç√√ ?
? ƒ ε
• Auxiliary knowledge • Laplacian noise generation
[Dwork et al 2006] • Independent noise generation:
Can be applied to cosine-similarity based measures
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To take away
Personalization is needed
Decentralization is healthy
Gossip-based computing is one (the) way to go
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Thank you
www.gossple.fr Joint work with M. Alaggan, A. Boutet, D. Frey, S.
Gambs, A. Jégou (INRIA), R. Guerraoui (EPFL)