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Community Meeting 2: Online voting with Decidim

Avatar: Official meeting
Official meeting

This summer we will release a new module that will allow online voting with Decidim. We wanted to share the different complexities we have encountered and open the debate on the challenges posed by these voting systems.

Watch the session here (in Spanish)

The team behind this development presented the new module:

  • Eva Solà and Oriol Gual from Codegram
  • Andrés Pereira de Lucena (Technological advisor of Decidim).

We invited the following experts to contribute to the conversation from the technological, cryptographic and academic fields. 

  1. Ferran Reyes, Communication and Community Lead at Vocdoni, a platform that builds governance solutions and a universally verifiable, anonymous and scalable digital voting system.
  2. David Dueñas, Assistant Professor at MINDS (Management in Networked and Digital Societies) department of Kozminski University and the NeRDS (New Research on Digital Societies) group.
  3. Vanesa Daza, Senior Lecturer at Pompeu Fabra University. Researcher in cryptology, crypto-security and blockchain.
  4. Xavier Puig, CIO of the Department of External Action, Institutional Relations and Transparency of the Generalitat de Catalunya.
  5. Paz Morillo, mathematician. Associate Professor at the Universitat Politècnica de Catalunya. Member of the MAK research group (Mathematics Applied to Cryptography).

📂 Technical documentation


The activity was held in Spanish, but here are some notes in English written by Oliver Azevedo:

Presentación: Por qué voto electrónico con Decidim (Andrés)
Introducción al voto electrónico (definiciones, propiedades, etc.) y por qué voto electrónico con Decidim
Download file

Structure of the meeting

1. Welcome, intro, demo and development's presentation [11:00 - 11:35]

2. A dialogue with the experts [11:35 - 12:35]

3. Q&A [12:35 - 12:55]

4. Wrap-up [12:55 - 13:00]

Meeting Minutes

/ How it works

  • The new functionality developed integrates two levels:
  • Component "elections": It can be enabled within any participation space in Decidim. Open census and online voting.
  • Voting space: Voting can be online, in person or hybrid. Configurable home page and management of voting points in person. Management of the census in Decidim, it will not be necessary to be registered to decide.
  • The participant will be able to check if they are in the census and can vote: They will have to enter their data to check if they have the right to vote, and they will have to do a two-step authentication process.
  • An access code will be generated for each participant.
  • Once voted, each voter will be able to audit the ballot by generating a unique code.

/ Demo and Architecture

  • An agnostic solution has been made: The Bulletin Board is the center of everything, validates the vote count and sends it to decide for publication.
  • This allows everyone to decide which cryptographic scheme to use.
  • The trustees manage the encryption keys for the final sum, guaranteeing voting secrecy thanks to the homomorphic sum.
  • Voters are able to verify their own votes, and election officials are able to audit the voting results through key fragments that they hold.
  • E-voting functionality is split between an elections module and a bulletin-board API, which together enable encrypted and verifiable voting, and auditable results, on Decidim. 
  • The bulletin-board API wraps around Microsoft's open source ElectionGuard, which applies homomorphic encryption to votes, and calculates tallies.
  • From Decidim we can follow all the steps that take place in the Bulletin Board.
  • Steps to configure a vote:
  • Election Setup: Configuration of questions and answers, census, etc. Once this is done, the key ceremony must be configured with the trustees that have been defined.
  • Voting: Voting time.
  • Tally: Vote count. The BulletinBoard calculates the results through homomorphic sums and sends the encrypted results to decidim for publication.

/ Dialogue with experts

  • Paz and Vanessa (Cryptographers): They consider that the security scheme is correct. Doubts are raised about the fragmentation of the keys (partial keys) to do the decryption. From a theoretical point of view, this fragmentation does not provide more security, it is unnecessary.
  • Eva (Codegram): Compensation is what allows threshold decryption.
  • Arnau (decidim): It is an element that gives us peace of mind in case the keys are lost.
  • Ferran (VocDoni) and Xavi Puig (GenCat): They pose the challenge of communicating and explaining to the public how these electronic voting systems work. In order to build trust in electronic voting.
  • Andrés and Arnau (Decidim): The fact that the code is open and auditable is one of the trusted sources. There is a more psychological legitimacy, which is gained by putting the electronic voting system into practice at smaller scales, such as universities, neighborhood associations, etc.
  • David Dueñas: It is important that the vote count is observable. Decidim will play a central role in the normalization of electronic voting, thanks to the processes where it is already being used.
  • VocDoni anonymizes the census, Decim anonymizes the vote. These two projects are in contact to explore ways of collaboration.

Based on the notes written by Oliver Azevedo:


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