SQIsign-webGPU

Browser-only SQIsign loaders that run the same Emscripten WASM as loadSqisignLvl*(), inside a dedicated Worker when the page is cross-origin isolated. This is not GPU-accelerated signing today.

:::important What this path actually does

• Crypto: identical SQIsign WASM (L1 / L3 / L5).
• Worker: keeps signing off the main thread when COOP/COEP + SharedArrayBuffer + WebGPU are available.
• WebGPU: device warmup only (compute shader smoke test) — no field arithmetic on GPU yet. Warmup buffers hold dummy constants, then are overwritten and destroyed; they never receive keys. See the threat model.
• SharedArrayBuffer: required for feature gating; not used for crypto buffers in the current code. :::

For reviewer detail (RNG, tests, provenance), see SQIsign WASM toolchain.

Level	Standard	Browser worker path
L5	loadSqisignLvl5()	loadSqisignLvl5WebGpu() → label SQISign-L5-webGPU
L3	loadSqisignLvl3()	loadSqisignLvl3WebGpu() → label SQISign-L3-webGPU
L1	loadSqisignLvl1()	loadSqisignLvl1WebGpu() → label SQISign-L1-webGPU

Labels: SQISIGN_WEBGPU_VARIANT_LABELS.

Requirements (COOP / COEP)

Needs a cross-origin isolated context:

1. crossOriginIsolated === true
2. SharedArrayBuffer available
3. navigator.gpu (WebGPU)

Cross-Origin-Opener-Policy: same-origin
Cross-Origin-Embedder-Policy: require-corp

:::danger Production caution require-corp breaks third-party scripts, analytics, iframes, and cross-origin images unless they send Cross-Origin-Resource-Policy. Prefer standard WASM loaders on the backend unless you need the worker isolation model. :::

:::warning Security unknowns A future GPU field path would not inherit upstream constant-time proofs. Today’s WebGPU step does not perform signing math. :::

Next.js headers example

// next.config.mjs
async headers() {
  return [
    {
      source: "/your-pqc-page/:path*",
      headers: [
        { key: "Cross-Origin-Opener-Policy", value: "same-origin" },
        { key: "Cross-Origin-Embedder-Policy", value: "require-corp" },
      ],
    },
  ];
}

Worker script

Bundlers cannot load sqisign-accel-worker.js from node_modules as a worker URL. Copy it to a public path:

cp node_modules/quantum-resistant-rustykey/dist/sqisign-accel-worker.js public/pqc/

Default URL: /pqc/sqisign-accel-worker.js. Override with:

import { setSqisignAccelWorkerUrl } from "quantum-resistant-rustykey";
setSqisignAccelWorkerUrl("/your/path/sqisign-accel-worker.js");

If the worker fails to load, the library falls back to main-thread WASM (still not GPU). Check getSqisignWebGpuSupport() first.

Usage

loadSqisignLvl*WebGpu().keypair() / .sign() throw in the page (same gate as the other signature loaders). Browser keygen/sign use the OPFS encrypted-sk wallet with algorithm ids sqisign-lvl*-webgpu (still WASM; no keys on the GPU). verify() and getSqisignWebGpuSupport() stay available. benchSqisignWebGpu() is gated the same way.

import {
  getSqisignWebGpuSupport,
  loadOpfsSkWallet,
  loadSqisignLvl5,
  opfsSkTriggerWebAuthn,
  setOpfsSkWorkerUrl,
  OPFS_SK_SLOT_SD_BUNDLE,
} from "quantum-resistant-rustykey";

const support = getSqisignWebGpuSupport();
if (!support.available) {
  console.warn(support.reason);
}

setOpfsSkWorkerUrl("/pqc/opfs-sk-worker.js");
const { prf } = await opfsSkTriggerWebAuthn({
  mode: "get",
  publicKey: authenticationOptions, // RP options used prf: {}
  salt,
});
const wallet = await loadOpfsSkWallet();
const msg = new TextEncoder().encode("hello");
const { public_key } = await wallet.keygen("sqisign-lvl5-webgpu", prf, {
  slot: OPFS_SK_SLOT_SD_BUNDLE,
});
const sig = await wallet.sign("sqisign-lvl5-webgpu", msg, prf, {
  slot: OPFS_SK_SLOT_SD_BUNDLE,
});
const sq = await loadSqisignLvl5();
const ok = await sq.verify(sig, msg, public_key);

Live side-by-side timings: pqc.rustykey.me.