Hash Miner

A browser-based SHA-256 Proof-of-Work (PoW) demo implemented with WebGPU and WebAssembly SIMD.

Demo

https://etherdream.github.io/hash-miner/

Usage

Challenge is the puzzle input. It can be specified manually or generated randomly. For simplicity, its length is fixed at 16 bytes.

Nonce is the solution. Click Start to begin searching for a nonce such that the first Difficulty bits of SHA256(Challenge || Nonce) are all zero. The UI displays values in hexadecimal.

In Config, you can configure the GPU and CPU utilization. Since the GPU is typically an order of magnitude faster than the CPU, running the CPU at 100% usually doesn’t help and can make the system sluggish.

In Debug, you can choose legacy APIs. The GPU backend supports WebGL2, and the CPU backend supports non-SIMD Wasm as well as asm.js.

History

In 2017, I wrote a WebGL2-based demo (link). That program was put together in a rush, so it had a few issues:

• An unreasonable canvas size prevented the GPU from being fully utilized.

• The SHA-256 message schedule W only needs 16 elements, not 64.

• Readbacks on every frame are unnecessary; instead, use an ANY_SAMPLES_PASSED query to count discards, and only read back pixels once a match is found.

This version fixes those issues, allowing the WebGL2 backend to reach WebGPU-level performance. (On macOS the performance is similar, but on Windows WebGPU is much faster than WebGL2.)

Project Layout

src/assets contains the Wasm binaries and shader files.

• webgl2.glsl

• webgpu.wgsl

The Wasm source code is located in sha256.cpp. The SIMD version utilizes wasm-vec4.h, which encapsulates vector operations in WGSL-style.

To recompile the Wasm files, execute the following command:

./build-wasm.sh

Since Emscripten no longer supports asm.js, this script currently cannot generate the asm.js build automatically. You need to extract it manually from asmjs-tmp.js.

The core modules are written in TypeScript and live in the src directory. Run npm run dev or npm run build to generate index.js in the dist directory.

Known Issues

On Chrome, non-SIMD Wasm performance is very poor — sometimes even slower than asm.js.