Poseidon in WGSL

This repository contains code which allows you to compute Poseidon hashes in your GPU. The code is written in WGSL, a shader programming language that works with WebGPU.

This implementation of the Poseidon hash targets the BN254 scalar field, with the following parameters:

• Number of inputs: 1
• t = 2
• n_rounds_f = 8
• n_rounds_p = 56

The results from this implementation should match those of the circomlibjs implementation on BN254.

Credits

Much of the big integer and finite field code was adapted from msm-webgpu by Sampriti Panda, Adhyyan Sekhsaria, and Nalin Bhardwaj.

The structure of the Poseidon WGSL code was inspired by poseidon-ark by arnaucube.

Getting started

Clone this repository, navigate to the project directory, and run:

cargo test test_poseidon -- --nocapture

You should see output like this:

Computing 16384 Poseidon hashes in Rust / WebGPU
CPU took 416ms
AdapterInfo { name: "Quadro P520", vendor: 4318, device: 7476, device_type: DiscreteGpu, driver: "NVIDIA", driver_info: "535.54.03", backend: Vulkan }
GPU took 88ms
test poseidon::test_poseidon ... ok

The time taken by the GPU to compute a hash the first time you run this command may be slower than the time it takes during subsequent runs. This may be due to the GPU caching the shader code.

This code has been successfully tested with an Nvidia Quadro P520 with 2GB memory on a Ubuntu Linux machine with version 535.54.03 of the Nvidia driver.

The code also runs on the same machine's Intel(R) UHD Graphics 620 (WHL GT2) integrated GPU with the Mesa v22.2.5 driver, but takes about 1100ms.

Poseidon hash using WebGPU in the browser

The following was tested with Firefox Nightly 117.0a1 (2023-07-15) (64-bit).

Enter about:config in the address bar and set the following to true:

• dom.webgpu.enabled
• gfx.webgpu.force-enabled

Next, in the command line, navigate to the web subdirectory:

cd web

Install dependencies:

npm i

Run the web server:

npx parcel index.html

Navigate to the URL that appears and viola! You should see something like the following:

Computing 16384 Poseidon hashes in the browser / WebGPU
CPU took 1267 ms
GPU took 103 ms