This code demonstrates a minimal example of how to use the RISC Zero zkVM to make ZK proofs about chess.
The demo uses the shakmaty crate to prove that a chess position has a checkmate without revealing what that checkmate is.
First, follow the examples guide to install dependencies and check out the correct version of the example.
Then, run the example with:
cargo run --releaseCongratulations! You just constructed a zero-knowledge proof that the position defined here includes a mate-in-one.
By using this demo as part of a Bonsai application, you could build an app where on-chain payment depends on off-chain activity. For example, you might issue an on-chain award for the first person who can find a mate-in-one.
To learn more about this use case, check out our Twitter thread about using Bonsai as a zk coprocessor.
zkVM applications are organized into a host program and a guest program.
The host program can be found in src/main.rs, and the guest program can be found in methods/guest/src/main.rs.
The host first executes the guest program and then proves the execution to construct a receipt. The receipt can be passed to a third party, who can examine the journal to check the program's outputs and can verify the receipt to ensure the integrity of the guest program's execution.
This is a simple zkVM application that demonstrates how to use a Rust crate inside the zkVM. Here, we use the shakmaty crate, which makes it possible to handle chess notation and chess logic. To learn more about using Rust crates inside the zkVM, check out our Rust Resources page.
The guest code generates the pos that results from a given move on a given board, and then checks that pos is checkmate.
The host code supplies the move and the board.
The host code supplies a move that the guest code keeps private and an initial board state that the guest code publishes to the journal. There are default values for these, but you can also pass in an alternative move and/or board state as command line arguments. The move is in SAN format and the board state is in FEN format.
The guest code checks that applying the move to the initial board state is legal and results in a checkmate. If not, the guest code asserts and no journal is produced.
- For a video walk-through of this example, check out this excerpt from our workshop at ZK HACK III.
- For more information about building, running, and testing zkVM applications, see our developer docs.