A Decentralized and Distributed E-voting Scheme Based on - - PowerPoint PPT Presentation

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A Decentralized and Distributed E-voting Scheme Based on - - PowerPoint PPT Presentation

Nov 03, 2023 230 likes •448 views

A Decentralized and Distributed E-voting Scheme Based on Cryptographic Shuffles Decentralized and Distributed Systems Laboratory Andy Caforio Responsible: Prof. Bryan Ford Supervision: Linus Gasser, Philipp Jovanovic 1 Way back when

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A Decentralized and Distributed E-voting Scheme Based on Cryptographic Shuffles

Decentralized and Distributed Systems Laboratory Andy Caforio Responsible: Prof. Bryan Ford Supervision: Linus Gasser, Philipp Jovanovic

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Way back when…

2 [https://heliosvoting.org/]

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Helios

  • Started in 2008
  • First web-based, verifiable e-voting scheme
  • Leverages cryptographic shuffles

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Helios - Features

  • Auditable elections

○ Encryption proof ○ Shuffle proof (Sako-Kilian) ○ Decryption proof

  • User authentication
  • Front- and back-end implementation

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Helios - Verifiability

  • Users can verify that their vote was counted
  • Shuffle weeds out malicious servers
  • Honest servers will perform decryption

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Helios - Protocol

1. Cast 2. Publish 3. Shuffle 4. Audit 5. Decrypt 6. Tally

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Helios - Disclaimer

  • Helios does not enforce anonymity
  • Voters may be subject to coercion

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Helios - Downsides

  • Centralized
  • Conventional database storage
  • Very slow shuffles

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Helios - Improvements

  • Centralized Cothority
  • Conventional database storage Skipchains
  • Very slow shuffles Neff

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Back to the future

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Protocols - DKG

  • Distributed Key Generation
  • Create public/private key pair
  • Split private key
  • Part of kyber library

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Protocols - Neff Shuffle

  • Novel verifiable shuffle concept by Andrew Neff
  • Orders of magnitude faster than Sako-Kilian scheme

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Protocols - Decryption

  • After election termination and audit
  • Reconstruct plaintext ballots with shared secret keys
  • Cannot be done by a single node

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Storage

  • Master

○ System configurations ○ List of admins, roster etc.

  • Link

○ Reference to election skipchain

  • Election

○ Settings ○ DKG public key, list of voters etc.

  • Ballot

○ Casted vote (one per block)

  • Shuffle

○ Permuted and re-encrypted ballots

  • Decrypt

○ Ballot plaintexts

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Practical

  • Go implementation
  • Built on top of cothority and kyber
  • Protobuf API

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Benchmarks - Helios

  • Shuffle of 500 ballots ~130s
  • 2.2 GHz dual core machine

16 [Ben Adida. Helios: Web-based open-audit voting]

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Benchmarks

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  • Shuffle
  • 1.4 GHz dual core
  • Real world context?
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Overview

  • Distributed e-voting scheme
  • Improves on Helios

○ Distributed ○ Faster

  • Built on top of DEDIS infrastructure

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Gory details

  • Cryptographic background

○ Framework (elliptic curve etc.) ○ Shuffles ○ Verifiability

  • Protocols

○ Networking

  • Usage

○ Authentication ○ Front-end

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References

  • Repository: https://github.com/dedis/student_17_evoting
  • Report: https://github.com/dedis/student_17_evoting/blob/master/report.pdf

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