Do dummies pay off? Limits of dummy traffic protection in anonymous - - PowerPoint PPT Presentation

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Do dummies pay off? Limits of dummy traffic protection in anonymous - - PowerPoint PPT Presentation

Sep 19, 2023 206 likes •404 views

Do dummies pay off? Limits of dummy traffic protection in anonymous communication systems Simon Oya , Carmela Troncoso and Fernando Prez-Gonzlez Introduction Anonymous channels hide correspondences (input/output). Dummies are a common

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Do dummies pay off?

Limits of dummy traffic protection in anonymous communication systems

Simon Oya, Carmela Troncoso and Fernando Pérez-González

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Introduction

  • Anonymous channels hide correspondences (input/output).
  • Dummies are a common protection mechanism.

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Motivation

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System Model

  • Basic pool-mix scenario
  • Firing condition: triggers the flushing of messages.
  • Batching strategy: how messages are chosen from the pool.
  • Sender-based dummies: die at the mix.
  • Mix-based dummies: generated by the mix.
  • (This was one communication round)

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System Model. Adversary.

  • Goal: infer
  • She cannot see the content of the messages…
  • … but she can see the number of

messages sent/received.

  • She is aware of the system parameters:
  • Mix behavior
  • Dummy policy
  • bserves ρ

communication rounds

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Least-Squares Estimator

  • Goal: infer all
  • Information:
  • Idea: minimize output error:
  • Expanding
  • Rem. Constraints

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Pool + Dummies :probabilities ρ rounds ρ rounds

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Performance Analysis. MSE.

  • Derive an expression for:
  • Assumptions:
  • MSE formula:

Observations Pool Sender Receiver

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Performance Analysis. Interpretation (I).

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Performance analysis. Interpretation (II).

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Performance analysis. Interpretation (II).

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Performance analysis. Interpretation (II).

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Designing dummy traffic strategies.

  • We understand the effect of the dummies in the

MSE.

  • Privacy objective
  • As an example: we pick two objectives.
  • Assumptions:
  • Budget of dummies

Dummy Strategy!

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PICK YOUR FAVOURITE PRIVACY OBJECTIVE!!

  • Return channel
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Dummy Strategy 1.

  • Objective: increase the protection of all the relations by a

constant factor.

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Dummy Strategy 1.

  • Solution: assign dummies proportionally to message rates.
  • Experimental results:

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Design Strategy 2.

  • Objective: provide a minimum protection as large as

possible.

Sender-based dummies Both kinds

  • f dummies

Receiver-based dummies Unaffected

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Dummy Strategy 2.

  • Solution: waterfilling-like algorithm.
  • Experimental Results

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  • Conclusions. Methodology.

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Thanks!

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simonoya@gts.uvigo.es