Anonymous GitHub GPG Voting Protocol built with Risc0

Cypher-poll is an anonymous voting protocol which anyone with a GitHub identity and at least one associated GPG key can use. The service can be modified to enforce further restrictions on who is eligible to vote, by default any GitHub account with a GPG key can vote once (not once per GPG key!).

Registration process

The registration process consists of the user submitting their Identity, which is a Hash of their unique Nullifier concatenated by their Public Key. If the user successfully generates a Signature for a Public Key that is associated with their GitHub account, the Hash of the Nullifier and Public Key is inserted in a fixed size Merkle Tree. A Snapshot of the Merkle Tree at that point in time is returned to the user.

Voting process

To issue a vote, the user must submit a zero knowledge proof that the Nullifier that is being redeemed was included in the Merkle Tree for a given Snapshot. The Snapshot that was returned by the server at the end of the registration process is sufficent as long as the corresponding Merkle Root is included in the set of valid Merkle Roots in service (or Blockchain) state.

If the proof is accepted, the vote is counted and the Nullifier is added to a list to ensure that it cannot be used again.

Generate and Export a GPG key

gpg --full-generate-key
gpg --armor --export-secret-keys keyID_or_email > private_key.sec.asc
gpg --armor --export keyID_or_email > public_key.asc

Specify Github API Token

Example .bashrc:

export GITHUB_TOKEN="YOUR_API_TOKEN_WITH_PGP_READ_PERMISSION"

Click here to generate an access token.

Run the Server

cargo run -p service

Client Documentation

cargo run -p client

This will print all the available commands (register, vote)

Example commands can be found in scripts, review them to make sure to change the user-specific inputs (username, public-key-path, private-key-path, random-seed, data).

The Client will write the Nullifier and Snapshot for the vote are to files, therefore environment variables must be present:

export NULLIFIER_PATH="/Users/chef/Desktop/cypher-poll/artifacts/nullifier"
export SNAPSHOT_PATH="/Users/chef/Desktop/cypher-poll/artifacts/snapshot"

Complete .bashrc:

export GITHUB_TOKEN="YOUR_API_TOKEN_WITH_PGP_READ_PERMISSION"
export NULLIFIER_PATH="/Users/chef/Desktop/cypher-poll/artifacts/nullifier"
export SNAPSHOT_PATH="/Users/chef/Desktop/cypher-poll/artifacts/snapshot"

Client Arguments Meaning

data	*-key-path	random-seed	username
challenge to be signed with the gpg key	path to a gpg key encoded in .asc (ASCII)	seed used to generate a unique nullifier, must be random and kept secret	github username

The vote Argument

The vote must be the same for both register and vote. With vote a leaf in the Tree is redeemed that was inserted during register. Trying to redeem an invalid vote will result in an error => an incorrect leaf.