2. 17/11/2011
The case of privacy in social CARTES & IDentification
networks Antoine Fressancourt
▶ Rising concern around privacy in
social networks
– Use of private information for
advertising purposes
– Applications gaining access to
more and more personal
information
– Usage tracking using referral
buttons
– Access to information directly
using URL, content not ciphered
▶ More and more complex to
manage
– Groups
– Possibility to specify target groups
on social network updates Adapted from The History Of Facebook’s
Default Privacy Settings by Matt McKeon
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3. 17/11/2011
A recent case: CARTES & IDentification
Europe vs. Facebook
vs Antoine Fressancourt
▶ Case raised by Max
Schrems, a 24 years old
law student against
Facebook
▶ Discovered that
Facebook keeps track of
every digital trace of a
user, even when they
are “deleted”
deleted
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4. 17/11/2011
Highlighted issues CARTES & IDentification
Antoine Fressancourt
Those examples tend to highlight two issues
Privacy
inside the social network itself
Data privacy from
outside the social network
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5. 17/11/2011
Anatomy of a social network CARTES & IDentification
Functional building blocks Antoine Fressancourt
Management of user
Identity credentials and attributes
d i l d ib
Privacy policy
Role management for users i.e.
Profile(s) how they want to appear
Management of a user’s
Social graph
g p relationships
Synchronous and asynchronous
Messaging
g g messages for a user
g
P
Storage of documents
Repository associated to a user
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6. 17/11/2011
Potential solutions CARTES & IDentification
Antoine Fressancourt
Cypher information
Privacy
P i inside the network itself
inside the social to protect from the SNS
network it lf
t k itself provider
Use identity
Data privacy from management concepts
and zero knowledge
outside the
approaches to secure
social network exchanges with external
sites
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7. 17/11/2011
Privacy inside the social network CARTES & IDentification
Review of academic solutions Antoine Fressancourt
Mainly two families of approaches:
▶ « add-in » applications
– FlyByNight: Re-Encryption proxy, El Gamal encryption, AES
– NOYB: Replace each attribute of a given user by an attribute of another
member of its social network
– FaceCloak: Dictionnary, MAC
▶ « Privacy by Design » social networks
– Persona: Attribute-Based Encryption
– EASiER: Attribute-Based Encryption
– A Collaborative Framework for Privacy Protection in Online Social
Network: El Gamal
– Cryptographic Treatment of Private User Profiles: Broadcast Encryption
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8. 17/11/2011
Our proposal CARTES & IDentification
Solving the « inside » privacy issue Antoine Fressancourt
Using a Cypher text Policy Attribute
Based Encryption (CP-ABE) scheme to
(CP ABE)
cypher the data inside the social network
▶ Advantages
– Allows us to d f
ll define privacy policies b
l based
d
on fine grained predicates
– Englobate both Identity-based encryption
and Identity based broadcast encryptions
– Ease of deployment given our objectives
▶ Drawback
– Keys and cypher texts are longer than in
simpler, IBE schemes
– Heavy management of cryptographic keys
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9. 17/11/2011
What is IBE? CARTES & IDentification
Identity based encryption Antoine Fressancourt
▶ Identity based encryption:
▶ Proposed by Shamir in 1984
▶ Encrypt a message using any
arbitrary string as the key. (Message)bob@mail.com
▶ The string can be a
representation of the user’s
identity
▶ Principle:
▶ Alice encrypt a message with
Bob’s e-mail address
▶ Bob asks a PKG (Private Key Private Key h
Authentication
Generator) to provide a private
key associated to his e-mail
address. PKG
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10. 17/11/2011
What is ABE? CARTES & IDentification
Attribute based encryption Antoine Fressancourt
▶ Attribute based encryption is a
generalisation of identity AND
based encryption
▶ Encryption according
attributes:
▶ Personal: age, town, name… OR +18 y.o
▶ Relational: colleague, family,
friends, …
▶ Ciphertext-policy ABE:
▶ Cipher text possesses access
structure Colleague France
▶ Saving structures
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11. 17/11/2011
Privacy outside the social network CARTES & IDentification
What is needed Antoine Fressancourt
Possibility to register on
websites with credentials Use case of identity
provided to the social management systems
network
Social network External sites
Need to conform to
Recovery of user data in regulation, risk
various ways ( logs, related to user
cookies, …) acceptance
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12. 17/11/2011
What is Identity Management? CARTES & IDentification
Antoine Fressancourt
▶ Technologies, policies and
p
practices used to control
access to a resource by a
third party. User
▶ Three entities:
▶ Identity Provider (IdP):
maintains and gives access to
a user’s credentials
▶ S
Service P
i Provider (SP)
id (SP):
Consumes attributes provided
by an IdP
▶ User: Controls the distribution IdP SP
of its credentials by the IdP
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13. 17/11/2011
Use of identity management in a CARTES & IDentification
social network context Antoine Fressancourt
Use of concepts popularized by
Idemix and Uprove
▶ Anonymous credentials
▶ Zero-knowledge protocol Random value
– P otocol in which a p o e sho s to a
Protocol hich prover shows
verifier that he possesses an
erifier
rover
information without revealing it. Challenge
– Introduced by Goldwasser Micali and
Goldwasser,
Ve
Pr
Rackoff in 1984.
▶ Minimal Disclosure Response
Generation on the fly
How to perform the
using a zero
proof calculation?
knowledge compiler
k l d il
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14. 17/11/2011
CACE: A zero knowledge compiler CARTES & IDentification
Antoine Fressancourt
Computer Aided Cryptography
Engineering:
▶ European Project
▶ ∑-protocols
▶ Composition techniques
▶ Certificates
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15. 17/11/2011
Our proposal CARTES & IDentification
Solving the « outside » privacy issue Antoine Fressancourt
Use of Identity Management
platform and protocols
▶ Ensure minimal disclosure of private
information
▶ Framework to manage the disclosure of
user credentials
Integration of a zero knowledge
g g
compiler
▶ Computing zero knowledge proofs on the
y
fly
▶ Enhance the protection of private
information through minimal disclosure.
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16. 17/11/2011
To conclude CARTES & IDentification
Antoine Fressancourt
▶ Social networks raise a number of issues related to data security and
privacy
▶ Two kinds of privacy issues
– From inside the social network itself
– From external sites outside the social network
▶ Inside privacy isssues can be solved by using ABE to protect data and
give it access only to authorized contacts
▶ Outside privacy issues can be solved by using identity management
protocols and systems
▶ Overall, better management of data privacy in future social network
services deployed using emerging standards
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