Acropolis - a ZKVM enabled voting mechanism

Authorized Anonymous Voting

Acropolis enables anonymous voting through Signatures over Public Keys. The cryptographic identity of each user is treated as a secret input and never revealed to the public. Only the Signature issued by an authority for a "KYC-ed" user, alongside with the corresponding Public Key (one Public Key per election that is owned by the authority) are published for each election. An election is defined as a cycle with a fixed set of options to choose from and authorized identities (=Signatures over Public Keys).

The primary identifier of an election is an authorized Public Key, that is unique for each election. The payload that is signed by the authority is the Public Key of the authorized voter concatenated with the election Public Key (which acts as salt).

Each authorized user may only vote once per election.

An eligible user may submit a vote for an election by generating a zero-knowledge proof where the public inputs are:

• The authority's Public Key associated with the election
• The salted signature of the user's public key produced by the authority
• The user's vote selection (a string)

The private inputs to the zero-knowledge proof are:

• The user's Public Key
• A signature of the user's vote selection

How It Works Exactly

We utilize a risc0 guest program (circuit) to construct the proof.

The risc0 guest program performs the following:

1. Validates, using the authority's Public Key, the signature of the user's public key concatenated with the authority's Public Key
2. Validates, using the user's Public Key, the signature of the user's vote selection

The Client

The Client can be used to issue identities, generate keypairs and submit votes.

cargo run -p acropolis

Usage: acropolis <COMMAND>

Commands:
  vote               
  generate-key-pair  
  issue-identity     
  help               Print this message or the help of the given subcommand(s)

Options:
  -h, --help  Print help

The Client crate has a groth16 feature that indicates whether to submit a proof to the api and ethereum, or just the api. Risc0-groth16 currently only supports x86 architecture and therefore this feature may not be enabled when running unsupported architecture.

Auditing the API

Our API serves all Elections and their Votes. An external entity can utilize the functionality exposed by our audit-utils crate to verify all ZKPs (=votes) independently. The client exposes an audit endpoint that can be used to verify a set of votes. We scrape the votes the Smart Contract and dump them to a file that is fully auditable. The audit will evaluate all votes, verify all Zero Knowledge Proofs, flag malicious voters and output legitimate election results.

Simple CLI Voting

First run the API and initialize Elections alongside with Accounts:

cargo run -p api

Open another terminal (or split tmux) and submit a vote:

cargo run -p acropolis -- --user-id-path ./election-1/user-1 --vote "dogs_and_cats"

Proving will take some time, once finished the API will serve the current state of the election. To query elections:

http://127.0.0.1:8080/fetch_elections

To query all votes (+ ZK proofs) of an election that have been verified by the API:

http://127.0.0.1:8080/fetch_votes/<election_hex>

Get an overview (TUI)

Again, make sure the API is running first:

cargo run -p api

Then run (in another shell):

cargo run -p tui

You'll get a window with a title that will show any errors (there won't be any if the API is running), a list of ongoing elections you can scroll through with arrow keys, and a bar graph showing the current results on teh right.

Additional Contributions

We hopefully improved the developer experience by submitting a PR that packages kurtosis with Nix: kurtosis-tech/kurtosis#2461