When voting over the internet, the voter needs to be able to verify that their vote was cast correctly. This avoids trusting their voting device fully. This project implements voter-side verification (also called individual verification) for POLYAS 3.0 (Version 1.3.2, 31 July 2023), following the second device spec (Version 1.2-SNAPSHOT, 22. September 2024). You can find the specification in the folder spec; this folder is excluded from the MIT license (the copyright remains at POLYAS). Note that the POLYAS system does only publish part of their specification (and notably no code and no formal proofs of the full system).

This project has been developed for the Gesellschaft für Informatik (German) and has been supported by the Université de Lorraine, CNRS, Inria, and LORIA (Nancy, France). In collaboration with other researchers, a scientific publication documents the experience of implementing this verifier (and others), and formulates recommendation for similar projects (paper).

After voting in the main voting system, the voter is presented with a QR code. Using this QR code, the voter is able to initialize a second device application (such as this project). The second device application then downloads the cast vote from the server, and shows it to the voter again. The voter can then verify their vote has been cast correctly.

Start	Enter password

Verify ballot voter id (to check indeed verifying own vote)	Verify ballot content (to check cast correctly)

After successful vote validation, there is an option to download the receipt or skip the step. An example of such a receipt is in assets/generated_receipt.pdf.

You can test this UI with the link as follows:

• Enter the following link: http://localhost:5173/verify?c=7bgIHYQotKLc8tgCbWp5yuc83xSbN-JV4Vwpnb50qyIzNUj2tYDYzPInG80WJ1mf2tB8BstZXWH_b0y4&vid=voter3&nonce=f299af96450db626754147aa132237bbf5603df2eea8215a0859288df8015c85
• Enter the password 123456

Then mock data client will kick in, which validates the vote.

The second device application outputs a receipt, which contains the fingerprint of the ballot, and a signature over said fingerprint. The receipt is typically sent to the auditors, which ensure then a ballot with this fingerprint is considered in the final voting result.

This project also allows to verify that signature; thereby proving that the voting server must know the referenced ballot.

Start	Valid receipt

Invalid receipt	Receipt help

You can test this UI with the receipt in assets/test_vote_receipt.pdf.

The backend is built using php (using the slim framework) and manages dependencies using composer. Quick start:

• composer install
• symfony server:start (see symfony CLI)

The frontend is built using JavaScript (using vue with TypeScript), manages dependencies using npm, and builds using vite. Quick start:

• npm install
• npm run dev

Then open localhost:5173 (pointing to the vite server started by npm run dev) to see the webpage. Note that only in this local environment, the vite server is running, in production php serves all files.

famoser/agnes is recommended to release and deploy.

You need access to the config repository specified in agnes.yml. Then:

• create a new release (here v1.0) of main branch with ./vendor/bin/agnes release v1.0 main
• deploy release to prod environment with ./vendor/bin/agnes deploy *:*:prod v1.0

The server needs to fulfil requirements specified in composer.json.

The following changes should be tackled:

• Describe clearly what IV is for, as users are likely not aware (see https://publikationen.bibliothek.kit.edu/1000175514/155244080)
• Use https://github.com/famoser/elliptic/ as a cryptography backend
• Ask POLYAS how to check that uploaded receipts are contained on the bulletin board of the POLYAS server