MPC Uniqueness Check

The MPC Uniqueness Check is a secure multi-party computation (SMPC) protocol that powers the matching engine behind Worldcoin's iris recognition inference system. SMPC is used to calculate a fractional hamming distance to determine uniqueness of a given iris code. A detailed specification of the iris code SMPC can be found here.

sequenceDiagram
    autonumber
    participant RequestQueue as Uniqueness Check Queue
    participant Coord as Coordinator
    participant Participants as Participants
    participant ResultsQueue as Results Queue

    RequestQueue ->> Coord: New uniquness check request
    Coord ->> Participants: Send code to all participants
    Coord ->> Coord: Sync latest masks from the database
    Coord ->> Coord: Calculate mask portion of FHD
    Participants ->> Participants: Sync latest shares from the database
    Participants ->> Participants: Calculate iris code portion of FHD
    Participants ->> Coord: Send partial results
    Coord ->> Coord: Calculate final result
    Coord ->> ResultsQueue: Enqueue final result

Loading

The MPC setup consists of a coordinator and n participants, where each participant stores an encrypted portion of each iris code and the coordinator stores the corresponding masks. When a new uniqueness check request is enqueued, the coordinator will send the code to each of the participants, which will compute a fractional hamming distance against their encrypted partial iris codes. The participant results will be sent back to the coordinator and the partial results will be combined to arrive at the final result.

Installing

To install mpc uniqueness check and all utilities, you can run the following command.

cargo install --path .

Usage

Coordinator

To start the coordinator, you can run mpc-node --config <path_to_config> or specify the following configuration via environment variables.

[coordinator]
# Socket addresses for each participant
participants = '["127.0.0.1:8000", "127.0.0.1:8001", "127.0.0.1:8002"]'
# Hamming distance threshold to determine if a given iris code is unique 
hamming_distance_threshold = 0.375
# Max duration allotted when connecting to participants
participant_connection_timeout = "1s"

# Database where the masks will be stored
[coordinator.db]
url = "postgres://localhost:5432/mpc"
migrate = true
create = false

# AWS configuration for the coordinator
[coordinator.aws]
endpoint = ""
region = ""

[coordinator.queues]
# Uniqueness check requests queue
queries_queue_url = "https://sqs.us-east-1.amazonaws.com/1234567890/mpc-query-queue"
# Uniqueness check results queue
distances_queue_url = "https://sqs.us-east-1.amazonaws.com/1234567890/mpc-distance-results-queue"
# Queue specifying masks to add to the database
db_sync_queue_url = "https://sqs.us-east-1.amazonaws.com/1234567890/mpc-query-queue"

Participant

To start the participant, you can run mpc-node --config <path_to_config>. Note that the command to run the participant is the same as the coordinator, however you will need to specify the following configuration variables instead.

[participant]
# Socket address for the participant
socket_addr = "127.0.0.1:8000"
# Batch size when calculating fractional hamming distance
batch_size = 20000

# Database where the shares will be stored
[participant.db]
url = "postgres://localhost:5432/participant_db"
migrate = true
create = false

# AWS configuration for the participant
[participant.aws]
endpoint = ""
region = ""

[participant.queues]
# Queue specifying shares to add to the database
db_sync_queue_url = "https://sqs.us-east-1.amazonaws.com/1234567890/participant-db-sync-queue"

Running Locally

To run a local version of the MPC uniqueness check with two participants, you can execute the following command. Note that you do not need to specify the configuration above as this is already included in the compose file.

docker compose up -d

Once all of the services are running, you can seed the coordinator and participant databases with random iris codes/masks.

utils seed-db -c postgres://postgres:[email protected]:5432/db -p postgres://postgres:[email protected]:5433/db --num 10000 --batch-size 1000

After seeding the databases, you can enqueue a random template to the coordinator queue which will orchestrate the MPC uniqueness check.

utils sqs-query -e http://localhost:4566 -q http://sqs.us-east-1.localhost.localstack.cloud:4566/000000000000/coordinator-uniqueness-check

License

Unless otherwise specified, all code in this repository is dual-licensed under either:

• MIT License (LICENSE-MIT)
• Apache License, Version 2.0, with LLVM Exceptions (LICENSE-APACHE)

at your option. This means you may select the license you prefer to use.

Any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.