Privacy-Enabling Social Networking Over Untrusted Networks Jonathan - - PowerPoint PPT Presentation

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Privacy-Enabling Social Networking Over Untrusted Networks Jonathan Anderson, Claudia Diaz * , Joseph Bonneau and Frank Stajano {jonathan.anderson,joseph.bonneau,frank.stajano}@cl.cam.ac.uk claudia.diaz@esat.kuleuven.be Computer Laboratory *

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SLIDE 1

Privacy-Enabling Social Networking Over Untrusted Networks

Jonathan Anderson, Claudia Diaz*, Joseph Bonneau and Frank Stajano {jonathan.anderson,joseph.bonneau,frank.stajano}@cl.cam.ac.uk claudia.diaz@esat.kuleuven.be Computer Laboratory

* K.U. Leuven ESAT/COSIC 1 Monday, August 17, 2009

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SLIDE 2

Outline

  • Social networks require absolute trust
  • Operators don’t protect their users
  • Smart clients can protect themselves
  • Protocols
  • Privacy
  • Performance

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SLIDE 3

Social Networks Require Absolute Trust

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SLIDE 4

Social Networks Require Absolute Trust

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SLIDE 5

Social Networks Require Absolute Trust

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SLIDE 6

Social Networks Require Absolute Trust

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SLIDE 7

Social Networks Require Absolute Trust

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SLIDE 8

Social Networks Require Absolute Trust

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SLIDE 9

Network Operators Don’t Protect Their Users

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SLIDE 10

Network Operators Don’t Protect Their Users

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SLIDE 11

Smart Clients Can Protect Themselves

  • Stop trusting the network!
  • Smart clients, dumb servers

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SLIDE 12

How Do You Facebook?

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SLIDE 13

How Do You Facebook?

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SLIDE 14

Decentralised Architecture

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SLIDE 15

Decentralised Architecture

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SLIDE 16

Decentralised Architecture

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SLIDE 17

Privacy Requirements

  • Protect content and links
  • Adversaries:
  • Other users
  • Application developers
  • Network operator
  • Reduce to social contract

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SLIDE 18

Software Architecture

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SLIDE 19

Software Architecture

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SLIDE 20

Software Architecture

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SLIDE 21

Application Layer

  • Sandboxed applications
  • Security API
  • Restrictive default policies
  • User policy specification

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SLIDE 22

Software Architecture

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SLIDE 23

Data Structures Layer

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SLIDE 24

Data Structures Layer

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SLIDE 25

Data Structures Layer

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SLIDE 26

Data Structures Layer

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SLIDE 27

Data Structures Layer

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SLIDE 28

Data Structures Layer

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SLIDE 29

Data Structures Layer

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SLIDE 30

Data Structures Layer

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SLIDE 31

Software Architecture

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SLIDE 32

Cryptography Layer

  • Encryption, digital signatures, etc.
  • Key Management
  • Identity Verification
  • Link Hiding

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SLIDE 33

Encrypted Blocks

  • Unique symmetric key per block per ACL revision
  • This sounds familiar...
  • No revocation guarantees

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SLIDE 34

Key Management

  • Direct distribution via PK
  • Key hierarchy
  • “Group key” blocks
  • Hidden links

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SLIDE 35

Link Hiding

03 00 4d 0b 59 7a e5 b0 7a bf 89 c8 f6 b0 2d 74 76 2d 30 64 67 9a 42 f6 34 15 bc 66 71 91 2a 34 0e e6 45 c4 ff 8f d7 90 95 4a e3 a8 2e

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SLIDE 36

Link Hiding

03 00 4d 0b 59 7a e5 b0 7a bf 89 c8 f6 b0 2d 74 76 2d 30 64 67 9a 42 f6 34 15 bc 66 71 91 2a 34 0e e6 45 c4 ff 8f d7 90 95 4a e3 a8 2e

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E

+

K1 E

+

K2

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SLIDE 37

Link Hiding

03 00 4d 0b 59 7a e5 b0 7a bf 89 c8 f6 b0 2d 74 76 2d 30 64 67 9a 42 f6 34 15 bc 66 71 91 2a 34 0e e6 45 c4 ff 8f d7 90 95 4a e3 a8 2e

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E

+

K1 E

+

K2

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SLIDE 38

Link Hiding

03 00 4d 0b 59 7a e5 b0 7a bf 89 c8 f6 b0 2d 74 76 2d 30 64 67 9a 42 f6 34 15 bc 66 71 91 2a 34 0e e6 45 c4 ff 8f d7 90 95 4a e3 a8 2e

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ad e6 e1 69 fd 4e 70 3c da ce f8 c6 94 0f e7 3c 6b 66 c5 39 6c 1c 74 c1 14 ef 53 L I N K : d e f .. .. 70 32 22 12 37 9d 92 e4 1e fb L I N K : a b c .. .. 92 71 44 99 1c ff bf d9 5a e1 03 08 8e 7d 9b c2 45 56 aa dd 0e 64 fc 7f a3 c4 77 77 e6 a0 81 c4 5a

E

+

K1 E

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K2

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SLIDE 39

Messaging

  • Asynchronous
  • Encryption
  • Signing
  • Synchronous
  • OTR

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SLIDE 40

Identity Verification

  • PKI
  • Web of Trust
  • Fingerprint Exchange
  • Multi-Channel Protocol

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SLIDE 41

Fingerprint Exchange

  • CryptoIDs
  • “a little longer than most email addresses, a little shorter than most

postal addresses, and about the same size as a credit card plus its 4- digit expiration date”

  • f3v4g.ifcen.r3rj5.embx8
  • small enough for a business card

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Mutual Identity Verification

  • Wong-Stajano protocol
  • Exchange of small nonces
  • Nonces can be cryptographically weak
  • Relies on data origin authenticity

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SLIDE 43

Joint Content

  • Digital signature convention
  • Sign content and context

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SLIDE 44

Software Architecture

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SLIDE 45

Network Layer

  • GET, POST
  • Access control
  • Not for confidentiality
  • Ok for integrity
  • Extra: mailboxes?

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SLIDE 46

Implementation

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SLIDE 47

Implementation

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SLIDE 48

Implementation

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SLIDE 49

Performance

  • Server
  • Storage scales (roughly) linearly with users
  • Computation scales linearly with storage
  • I/O-bound clients (branching factor)

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SLIDE 50

Open Problems

  • Usability of policy specification
  • End user development
  • Security API

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SLIDE 51

Discussion

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SLIDE 52

Appendix

  • Wong-Stajano protocol
  • Crypto performance

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SLIDE 53

Wong-Stajano Protocol

A → B : KA B → A : KB A → B : H(A | KA | KB | Ra | Ka) B → A : H(B | KA | KB | Rb | Kb) A ⇒ B : Ra B ⇒ A : Rb A → B : Ka B → A : Kb A ⇒ B : outcome B ⇒ A : outcome

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SLIDE 54

Crypto Performance

  • SunJCE v1.7 on Intel Core2 Quad CPU Q6600 @ 2.4 GHz
  • RSA
  • 1024b en/decryption @ 600 kB/s, 30 kB/s
  • 2048b RSA en/decryption @ 200 kB/s, 7 kB/s
  • AES: 128b @ 35 MB/s

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