refactor(web): redo proof of work web worker logic (#941)

* chore(web/js): delete proof-of-work-slow.mjs This code has served its purpose and now needs to be retired to the great beyond. There is no replacement for this, the fast implementation will be used instead. Signed-off-by: Xe Iaso <me@xeiaso.net> * chore(web): handle building multiple JS entrypoints and web workers Signed-off-by: Xe Iaso <me@xeiaso.net> * feat(web): rewrite frontend worker handling This completely rewrites how the proof of work challenge works based on feedback from browser engine developers and starts the process of making the proof of work function easier to change out. - Import @aws-crypto/sha256-js to use in Firefox as its implementation of WebCrypto doesn't jump directly from highly optimized browser internals to JIT-ed JavaScript like Chrome's seems to. - Move the worker code to `web/js/worker/*` with each worker named after the hashing method and hash method implementation it uses. - Update bench.mjs to import algorithms the new way. - Delete video.mjs, it was part of a legacy experiment that I never had time to finish. - Update LibreJS comment to add info about the use of @aws-crypto/sha256-js. - Also update my email to my @techaro.lol address. Signed-off-by: Xe Iaso <me@xeiaso.net> * fix(web): don't hard dep webcrypto anymore Signed-off-by: Xe Iaso <me@xeiaso.net> * chore(lib/policy): start the deprecation process for slow This mostly adds a warning, but the "slow" method is in the process of being removed. Warn admins with slog.Warn. Signed-off-by: Xe Iaso <me@xeiaso.net> * docs: update CHANGELOG Signed-off-by: Xe Iaso <me@xeiaso.net> * feat(web/js): allow running Anubis in non-secure contexts Signed-off-by: Xe Iaso <me@xeiaso.net> * Update metadata check-spelling run (pull_request) for Xe/purge-slow Signed-off-by: check-spelling-bot <check-spelling-bot@users.noreply.github.com> on-behalf-of: @check-spelling <check-spelling-bot@check-spelling.dev> --------- Signed-off-by: Xe Iaso <me@xeiaso.net> Signed-off-by: check-spelling-bot <check-spelling-bot@users.noreply.github.com>
2025-08-03 09:48:08 -04:00 · 2025-08-02 11:27:26 -04:00 · 2025-08-02 11:27:26 -04:00 · 0dccf2e009
commit 0dccf2e009
parent 8d08de6d9c
15 changed files with 337 additions and 289 deletions
--- a/.github/actions/spelling/expect.txt
+++ b/.github/actions/spelling/expect.txt
@ -141,6 +141,7 @@ httpdebug
 Huawei
 hypertext
 iaskspider
+iaso
 iat
 ifm
 Imagesift
@ -232,6 +233,7 @@ promauto
 promhttp
 proofofwork
 publicsuffix
+purejs
 pwcmd
 pwuser
 qualys
@ -309,7 +311,6 @@ Varis
 Velen
 vendored
 vhosts
-videotest
 VKE
 Vultr
 waitloop
--- a/docs/docs/CHANGELOG.md
+++ b/docs/docs/CHANGELOG.md
@ -19,6 +19,17 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - The [`segments`](./admin/configuration/expressions.mdx#segments) function was added for splitting a path into its slash-separated segments.
 - When issuing a challenge, Anubis stores information about that challenge into the store. That stored information is later used to validate challenge responses. This works around nondeterminism in bot rules. ([#917](https://github.com/TecharoHQ/anubis/issues/917))
 - When parsing [Open Graph tags](./admin/configuration/open-graph.mdx), add any URLs found in the responses to a temporary "allow cache" so that social preview images work.
+- Proof of work solving has had a complete overhaul and rethink based on feedback from browser engine developers, frontend experts, and overall performance profiling.
+- One of the biggest sources of lag in Firefox has been eliminated: the use of WebCrypto. Now whenever Anubis detects the client is using Firefox (or Pale Moon), it will swap over to a pure-JS implementation of SHA-256 for speed.
+- Web Workers are stored as dedicated JavaScript files in `static/js/workers/*.mjs`.
+- Pave the way for non-SHA256 solver methods and eventually one that uses WebAssembly (or WebAssembly code compiled to JS for those that disable WebAssembly).
+- Legacy JavaScript code has been eliminated.
+- The contact email in the LibreJS header has been changed.
+- The hard dependency on WebCrypto has been removed, allowing a proof of work challenge to work over plain (unencrypted) HTTP.
+
+### Breaking changes
+
+- The "slow" frontend solver has been removed in order to reduce maintenance burden. Any existing uses of it will still work, but issue a warning upon startup asking administrators to upgrade to the "fast" frontend solver.

 ## v1.21.3: Minfilia Warde - Echo 3

--- a/lib/policy/policy.go
+++ b/lib/policy/policy.go
@ -149,6 +149,10 @@ func ParseConfig(ctx context.Context, fin io.Reader, fname string, defaultDiffic
 			if parsedBot.Challenge.Algorithm == "" {
 				parsedBot.Challenge.Algorithm = config.DefaultAlgorithm
 			}
+
+			if parsedBot.Challenge.Algorithm == "slow" {
+				slog.Warn("use of deprecated algorithm \"slow\" detected, please update this to \"fast\" when possible", "name", parsedBot.Name)
+			}
 		}

 		if b.Weight != nil {
@ -163,6 +167,10 @@ func ParseConfig(ctx context.Context, fin io.Reader, fname string, defaultDiffic
 	}

 	for _, t := range c.Thresholds {
+		if t.Challenge != nil && t.Challenge.Algorithm == "slow" {
+			slog.Warn("use of deprecated algorithm \"slow\" detected, please update this to \"fast\" when possible", "name", t.Name)
+		}
+
 		if t.Name == "legacy-anubis-behaviour" && t.Expression.String() == "true" {
 			if !warnedAboutThresholds.Load() {
 				slog.Warn("configuration file does not contain thresholds, see docs for details on how to upgrade", "fname", fname, "docs_url", "https://anubis.techaro.lol/docs/admin/configuration/thresholds/")
--- a/package-lock.json
+++ b/package-lock.json
@ -8,6 +8,9 @@
      "name": "@techaro/anubis",
      "version": "1.21.3",
      "license": "ISC",
+      "dependencies": {
+        "@aws-crypto/sha256-js": "^5.2.0"
+      },
      "devDependencies": {
        "cssnano": "^7.1.0",
        "cssnano-preset-advanced": "^7.0.8",
@ -19,6 +22,44 @@
        "postcss-url": "^10.1.3"
      }
    },
+    "node_modules/@aws-crypto/sha256-js": {
+      "version": "5.2.0",
+      "resolved": "https://registry.npmjs.org/@aws-crypto/sha256-js/-/sha256-js-5.2.0.tgz",
+      "integrity": "sha512-FFQQyu7edu4ufvIZ+OadFpHHOt+eSTBaYaki44c+akjg7qZg9oOQeLlk77F6tSYqjDAFClrHJk9tMf0HdVyOvA==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@aws-crypto/util": "^5.2.0",
+        "@aws-sdk/types": "^3.222.0",
+        "tslib": "^2.6.2"
+      },
+      "engines": {
+        "node": ">=16.0.0"
+      }
+    },
+    "node_modules/@aws-crypto/util": {
+      "version": "5.2.0",
+      "resolved": "https://registry.npmjs.org/@aws-crypto/util/-/util-5.2.0.tgz",
+      "integrity": "sha512-4RkU9EsI6ZpBve5fseQlGNUWKMa1RLPQ1dnjnQoe07ldfIzcsGb5hC5W0Dm7u423KWzawlrpbjXBrXCEv9zazQ==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@aws-sdk/types": "^3.222.0",
+        "@smithy/util-utf8": "^2.0.0",
+        "tslib": "^2.6.2"
+      }
+    },
+    "node_modules/@aws-sdk/types": {
+      "version": "3.840.0",
+      "resolved": "https://registry.npmjs.org/@aws-sdk/types/-/types-3.840.0.tgz",
+      "integrity": "sha512-xliuHaUFZxEx1NSXeLLZ9Dyu6+EJVQKEoD+yM+zqUo3YDZ7medKJWY6fIOKiPX/N7XbLdBYwajb15Q7IL8KkeA==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@smithy/types": "^4.3.1",
+        "tslib": "^2.6.2"
+      },
+      "engines": {
+        "node": ">=18.0.0"
+      }
+    },
    "node_modules/@esbuild/aix-ppc64": {
      "version": "0.25.8",
      "resolved": "https://registry.npmjs.org/@esbuild/aix-ppc64/-/aix-ppc64-0.25.8.tgz",
@ -461,6 +502,56 @@
        "node": ">=18"
      }
    },
+    "node_modules/@smithy/is-array-buffer": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/@smithy/is-array-buffer/-/is-array-buffer-2.2.0.tgz",
+      "integrity": "sha512-GGP3O9QFD24uGeAXYUjwSTXARoqpZykHadOmA8G5vfJPK0/DC67qa//0qvqrJzL1xc8WQWX7/yc7fwudjPHPhA==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "tslib": "^2.6.2"
+      },
+      "engines": {
+        "node": ">=14.0.0"
+      }
+    },
+    "node_modules/@smithy/types": {
+      "version": "4.3.1",
+      "resolved": "https://registry.npmjs.org/@smithy/types/-/types-4.3.1.tgz",
+      "integrity": "sha512-UqKOQBL2x6+HWl3P+3QqFD4ncKq0I8Nuz9QItGv5WuKuMHuuwlhvqcZCoXGfc+P1QmfJE7VieykoYYmrOoFJxA==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "tslib": "^2.6.2"
+      },
+      "engines": {
+        "node": ">=18.0.0"
+      }
+    },
+    "node_modules/@smithy/util-buffer-from": {
+      "version": "2.2.0",
+      "resolved": "https://registry.npmjs.org/@smithy/util-buffer-from/-/util-buffer-from-2.2.0.tgz",
+      "integrity": "sha512-IJdWBbTcMQ6DA0gdNhh/BwrLkDR+ADW5Kr1aZmd4k3DIF6ezMV4R2NIAmT08wQJ3yUK82thHWmC/TnK/wpMMIA==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@smithy/is-array-buffer": "^2.2.0",
+        "tslib": "^2.6.2"
+      },
+      "engines": {
+        "node": ">=14.0.0"
+      }
+    },
+    "node_modules/@smithy/util-utf8": {
+      "version": "2.3.0",
+      "resolved": "https://registry.npmjs.org/@smithy/util-utf8/-/util-utf8-2.3.0.tgz",
+      "integrity": "sha512-R8Rdn8Hy72KKcebgLiv8jQcQkXoLMOGGv5uI1/k0l+snqkOzQ1R0ChUBCxWMlBsFMekWjq0wRudIweFs7sKT5A==",
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@smithy/util-buffer-from": "^2.2.0",
+        "tslib": "^2.6.2"
+      },
+      "engines": {
+        "node": ">=14.0.0"
+      }
+    },
    "node_modules/ansi-regex": {
      "version": "5.0.1",
      "resolved": "https://registry.npmjs.org/ansi-regex/-/ansi-regex-5.0.1.tgz",
@ -2515,6 +2606,12 @@
        "node": ">=8.0"
      }
    },
+    "node_modules/tslib": {
+      "version": "2.8.1",
+      "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.8.1.tgz",
+      "integrity": "sha512-oJFu94HQb+KVduSUQL7wnpmqnfmLsOA/nAh6b6EH0wCEoK0/mPeXU6c3wKDV83MkOuHPRHtSXKKU99IBazS/2w==",
+      "license": "0BSD"
+    },
    "node_modules/universalify": {
      "version": "2.0.1",
      "resolved": "https://registry.npmjs.org/universalify/-/universalify-2.0.1.tgz",
--- a/package.json
+++ b/package.json
@ -26,5 +26,8 @@
    "postcss-import": "^16.1.1",
    "postcss-import-url": "^7.2.0",
    "postcss-url": "^10.1.3"
+  },
+  "dependencies": {
+    "@aws-crypto/sha256-js": "^5.2.0"
  }
-}
+}
--- a/web/build.sh
+++ b/web/build.sh
@ -8,7 +8,7 @@ LICENSE='/*
@licstart  The following is the entire license notice for the
 JavaScript code in this page.

-Copyright (c) 2025 Xe Iaso <me@xeiaso.net>
+Copyright (c) 2025 Xe Iaso <xe.iaso@techaro.lol>

 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal
@ -28,6 +28,9 @@ LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.

+Includes code from https://github.com/aws/aws-sdk-js-crypto-helpers which is
+used under the terms of the Apache 2 license.
+
@licend  The above is the entire license notice
 for the JavaScript code in this page.
 */'
@ -36,9 +39,9 @@ for the JavaScript code in this page.
 mkdir -p static/locales
 cp ../lib/localization/locales/*.json static/locales/

-esbuild js/main.mjs --sourcemap --bundle --minify --outfile=static/js/main.mjs "--banner:js=${LICENSE}"
-gzip -f -k -n static/js/main.mjs
-zstd -f -k --ultra -22 static/js/main.mjs
-brotli -fZk static/js/main.mjs
-
-esbuild js/bench.mjs --sourcemap --bundle --minify --outfile=static/js/bench.mjs
+for file in js/*.mjs js/worker/*.mjs; do
+  esbuild "${file}" --sourcemap --bundle --minify --outfile=static/"${file}" --banner:js="${LICENSE}"
+  gzip -f -k -n static/${file}
+  zstd -f -k --ultra -22 static/${file}
+  brotli -fZk static/${file}
+done
--- a/web/js/algorithms/fast.mjs
+++ b/web/js/algorithms/fast.mjs
@ -0,0 +1,77 @@
+export default function process(
+  { basePrefix, version },
+  data,
+  difficulty = 5,
+  signal = null,
+  progressCallback = null,
+  threads = Math.max(navigator.hardwareConcurrency / 2, 1),
+) {
+  console.debug("fast algo");
+
+  let workerMethod = window.crypto !== undefined ? "webcrypto" : "purejs";
+
+  if (navigator.userAgent.includes("Firefox") || navigator.userAgent.includes("Goanna")) {
+    console.log("Firefox detected, using pure-JS fallback");
+    workerMethod = "purejs";
+  }
+
+  return new Promise((resolve, reject) => {
+    let webWorkerURL = `${basePrefix}/.within.website/x/cmd/anubis/static/js/worker/sha256-${workerMethod}.mjs?cacheBuster=${version}`;
+
+    console.log(webWorkerURL);
+
+    const workers = [];
+    let settled = false;
+
+    const cleanup = () => {
+      if (settled) {
+        return;
+      }
+      settled = true;
+      workers.forEach((w) => w.terminate());
+      if (signal != null) {
+        signal.removeEventListener("abort", onAbort);
+      }
+    };
+
+    const onAbort = () => {
+      console.log("PoW aborted");
+      cleanup();
+      reject(new DOMException("Aborted", "AbortError"));
+    };
+
+    if (signal != null) {
+      if (signal.aborted) {
+        return onAbort();
+      }
+      signal.addEventListener("abort", onAbort, { once: true });
+    }
+
+    for (let i = 0; i < threads; i++) {
+      let worker = new Worker(webWorkerURL);
+
+      worker.onmessage = (event) => {
+        if (typeof event.data === "number") {
+          progressCallback?.(event.data);
+        } else {
+          cleanup();
+          resolve(event.data);
+        }
+      };
+
+      worker.onerror = (event) => {
+        cleanup();
+        reject(event);
+      };
+
+      worker.postMessage({
+        data,
+        difficulty,
+        nonce: i,
+        threads,
+      });
+
+      workers.push(worker);
+    }
+  });
+}
--- a/web/js/algorithms/index.mjs
+++ b/web/js/algorithms/index.mjs
@ -0,0 +1,6 @@
+import fast from "./fast.mjs";
+
+export default {
+  fast: fast,
+  slow: fast, // XXX(Xe): slow is deprecated, but keep this around in case anything goes bad
+}
--- a/web/js/bench.mjs
+++ b/web/js/bench.mjs
@ -1,11 +1,6 @@
-import processFast from "./proof-of-work.mjs";
-import processSlow from "./proof-of-work-slow.mjs";
+import algorithms from "./algorithms/index.mjs";

 const defaultDifficulty = 4;
-const algorithms = {
-  fast: processFast,
-  slow: processSlow,
-};

 const status = document.getElementById("status");
 const difficultyInput = document.getElementById("difficulty-input");
@ -42,7 +37,7 @@ const benchmarkTrial = async (stats, difficulty, algorithm, signal) => {
    .join("");

  const t0 = performance.now();
-  const { hash, nonce } = await process(challenge, Number(difficulty), signal);
+  const { hash, nonce } = await process({ basePrefix: "/", version: "devel" }, challenge, Number(difficulty), signal);
  const t1 = performance.now();
  console.log({ hash, nonce });

--- a/web/js/main.mjs
+++ b/web/js/main.mjs
@ -1,10 +1,4 @@
-import processFast from "./proof-of-work.mjs";
-import processSlow from "./proof-of-work-slow.mjs";
-
-const algorithms = {
-  fast: processFast,
-  slow: processSlow,
-};
+import algorithms from "./algorithms/index.mjs";

 // from Xeact
 const u = (url = "", params = {}) => {
@ -75,11 +69,6 @@ const t = (key) => translations[`js_${key}`] || translations[key] || key;
  await initTranslations();

  const dependencies = [
-    {
-      name: "WebCrypto",
-      msg: t('web_crypto_error'),
-      value: window.crypto,
-    },
    {
      name: "Web Workers",
      msg: t('web_workers_error'),
@ -119,15 +108,6 @@ const t = (key) => translations[`js_${key}`] || translations[key] || key;
    progress.style.display = "none";
  };

-  if (!window.isSecureContext) {
-    ohNoes({
-      titleMsg: t('context_not_secure'),
-      statusMsg: t('context_not_secure_msg'),
-      imageSrc: imageURL("reject", anubisVersion, basePrefix),
-    });
-    return;
-  }
-
  status.innerHTML = t('calculating');

  for (const { value, name, msg } of dependencies) {
@ -171,6 +151,7 @@ const t = (key) => translations[`js_${key}`] || translations[key] || key;
  try {
    const t0 = Date.now();
    const { hash, nonce } = await process(
+      { basePrefix, version: anubisVersion },
      challenge,
      rules.difficulty,
      null,
--- a/web/js/proof-of-work-slow.mjs
+++ b/web/js/proof-of-work-slow.mjs
@ -1,99 +0,0 @@
-// https://dev.to/ratmd/simple-proof-of-work-in-javascript-3kgm
-
-export default function process(
-  data,
-  difficulty = 5,
-  signal = null,
-  progressCallback = null,
-  _threads = 1,
-) {
-  console.debug("slow algo");
-  return new Promise((resolve, reject) => {
-    let webWorkerURL = URL.createObjectURL(
-      new Blob(["(", processTask(), ")()"], { type: "application/javascript" }),
-    );
-
-    let worker = new Worker(webWorkerURL);
-    let settled = false;
-
-    const cleanup = () => {
-      if (settled) return;
-      settled = true;
-      worker.terminate();
-      if (signal != null) {
-        signal.removeEventListener("abort", onAbort);
-      }
-      URL.revokeObjectURL(webWorkerURL);
-    };
-
-    const onAbort = () => {
-      console.log("PoW aborted");
-      cleanup();
-      reject(new DOMException("Aborted", "AbortError"));
-    };
-
-    if (signal != null) {
-      if (signal.aborted) {
-        return onAbort();
-      }
-      signal.addEventListener("abort", onAbort, { once: true });
-    }
-
-    worker.onmessage = (event) => {
-      if (typeof event.data === "number") {
-        progressCallback?.(event.data);
-      } else {
-        cleanup();
-        resolve(event.data);
-      }
-    };
-
-    worker.onerror = (event) => {
-      cleanup();
-      reject(event);
-    };
-
-    worker.postMessage({
-      data,
-      difficulty,
-    });
-  });
-}
-
-function processTask() {
-  return function () {
-    const sha256 = (text) => {
-      const encoded = new TextEncoder().encode(text);
-      return crypto.subtle.digest("SHA-256", encoded.buffer).then((result) =>
-        Array.from(new Uint8Array(result))
-          .map((c) => c.toString(16).padStart(2, "0"))
-          .join(""),
-      );
-    };
-
-    addEventListener("message", async (event) => {
-      let data = event.data.data;
-      let difficulty = event.data.difficulty;
-
-      let hash;
-      let nonce = 0;
-      do {
-        if ((nonce & 1023) === 0) {
-          postMessage(nonce);
-        }
-        hash = await sha256(data + nonce++);
-      } while (
-        hash.substring(0, difficulty) !== Array(difficulty + 1).join("0")
-      );
-
-      nonce -= 1; // last nonce was post-incremented
-
-      postMessage({
-        hash,
-        data,
-        difficulty,
-        nonce,
-      });
-    });
-  }.toString();
-}
--- a/web/js/proof-of-work.mjs
+++ b/web/js/proof-of-work.mjs
@ -1,137 +0,0 @@
-export default function process(
-  data,
-  difficulty = 5,
-  signal = null,
-  progressCallback = null,
-  threads = Math.max(navigator.hardwareConcurrency / 2, 1),
-) {
-  console.debug("fast algo");
-  return new Promise((resolve, reject) => {
-    let webWorkerURL = URL.createObjectURL(
-      new Blob(["(", processTask(), ")()"], { type: "application/javascript" }),
-    );
-
-    const workers = [];
-    let settled = false;
-
-    const cleanup = () => {
-      if (settled) {
-        return;
-      }
-      settled = true;
-      workers.forEach((w) => w.terminate());
-      if (signal != null) {
-        signal.removeEventListener("abort", onAbort);
-      }
-      URL.revokeObjectURL(webWorkerURL);
-    };
-
-    const onAbort = () => {
-      console.log("PoW aborted");
-      cleanup();
-      reject(new DOMException("Aborted", "AbortError"));
-    };
-
-    if (signal != null) {
-      if (signal.aborted) {
-        return onAbort();
-      }
-      signal.addEventListener("abort", onAbort, { once: true });
-    }
-
-    for (let i = 0; i < threads; i++) {
-      let worker = new Worker(webWorkerURL);
-
-      worker.onmessage = (event) => {
-        if (typeof event.data === "number") {
-          progressCallback?.(event.data);
-        } else {
-          cleanup();
-          resolve(event.data);
-        }
-      };
-
-      worker.onerror = (event) => {
-        cleanup();
-        reject(event);
-      };
-
-      worker.postMessage({
-        data,
-        difficulty,
-        nonce: i,
-        threads,
-      });
-
-      workers.push(worker);
-    }
-  });
-}
-
-function processTask() {
-  return function () {
-    const sha256 = (text) => {
-      const encoded = new TextEncoder().encode(text);
-      return crypto.subtle.digest("SHA-256", encoded.buffer);
-    };
-
-    function uint8ArrayToHexString(arr) {
-      return Array.from(arr)
-        .map((c) => c.toString(16).padStart(2, "0"))
-        .join("");
-    }
-
-    addEventListener("message", async (event) => {
-      let data = event.data.data;
-      let difficulty = event.data.difficulty;
-      let hash;
-      let nonce = event.data.nonce;
-      let threads = event.data.threads;
-
-      const threadId = nonce;
-      let localIterationCount = 0;
-
-      while (true) {
-        const currentHash = await sha256(data + nonce);
-        const thisHash = new Uint8Array(currentHash);
-        let valid = true;
-
-        for (let j = 0; j < difficulty; j++) {
-          const byteIndex = Math.floor(j / 2); // which byte we are looking at
-          const nibbleIndex = j % 2; // which nibble in the byte we are looking at (0 is high, 1 is low)
-
-          let nibble =
-            (thisHash[byteIndex] >> (nibbleIndex === 0 ? 4 : 0)) & 0x0f; // Get the nibble
-
-          if (nibble !== 0) {
-            valid = false;
-            break;
-          }
-        }
-
-        if (valid) {
-          hash = uint8ArrayToHexString(thisHash);
-          console.log(hash);
-          break;
-        }
-
-        nonce += threads;
-
-        // send a progress update every 1024 iterations so that the user can be informed of
-        // the state of the challenge.
-        if (threadId == 0 && localIterationCount === 1024) {
-          postMessage(nonce);
-          localIterationCount = 0;
-        }
-        localIterationCount++;
-      }
-
-      postMessage({
-        hash,
-        data,
-        difficulty,
-        nonce,
-      });
-    });
-  }.toString();
-}
--- a/web/js/video.mjs
+++ b/web/js/video.mjs
@ -1,16 +0,0 @@
-const videoElement = `<video id="videotest" width="0" height="0" src="/.within.website/x/cmd/anubis/static/testdata/black.mp4"></video>`;
-
-export const testVideo = async (testarea) => {
-  testarea.innerHTML = videoElement;
-  return await new Promise((resolve) => {
-    const video = document.getElementById("videotest");
-    video.oncanplay = () => {
-      testarea.style.display = "none";
-      resolve(true);
-    };
-    video.onerror = () => {
-      testarea.style.display = "none";
-      resolve(false);
-    };
-  });
-};
--- a/web/js/worker/sha256-purejs.mjs
+++ b/web/js/worker/sha256-purejs.mjs
@ -0,0 +1,61 @@
+import { Sha256 } from '@aws-crypto/sha256-js';
+
+const calculateSHA256 = (text) => {
+  const hash = new Sha256();
+  hash.update(text);
+  return hash.digest();
+};
+
+function uint8ArrayToHexString(arr) {
+  return Array.from(arr)
+    .map((c) => c.toString(16).padStart(2, "0"))
+    .join("");
+}
+
+addEventListener('message', async ({ data: eventData }) => {
+  const { data, difficulty, threads } = eventData;
+  let nonce = eventData.nonce;
+  const isMainThread = nonce === 0;
+  let iterations = 0;
+
+  const requiredZeroBytes = Math.floor(difficulty / 2);
+  const isDifficultyOdd = difficulty % 2 !== 0;
+
+  for (; ;) {
+    const hashBuffer = await calculateSHA256(data + nonce);
+    const hashArray = new Uint8Array(hashBuffer);
+
+    let isValid = true;
+    for (let i = 0; i < requiredZeroBytes; i++) {
+      if (hashArray[i] !== 0) {
+        isValid = false;
+        break;
+      }
+    }
+
+    if (isValid && isDifficultyOdd) {
+      if ((hashArray[requiredZeroBytes] >> 4) !== 0) {
+        isValid = false;
+      }
+    }
+
+    if (isValid) {
+      const finalHash = toHexString(hashArray);
+      postMessage({
+        hash: finalHash,
+        data,
+        difficulty,
+        nonce,
+      });
+      return; // Exit worker
+    }
+
+    nonce += threads;
+    iterations++;
+
+    // Send a progress update from the main thread every 1024 iterations.
+    if (isMainThread && (iterations & 1023) === 0) {
+      postMessage(nonce);
+    }
+  }
+});
--- a/web/js/worker/sha256-webcrypto.mjs
+++ b/web/js/worker/sha256-webcrypto.mjs
@ -0,0 +1,57 @@
+const encoder = new TextEncoder();
+const calculateSHA256 = async (input) => {
+  const data = encoder.encode(input);
+  return await crypto.subtle.digest("SHA-256", data);
+};
+
+const toHexString = (byteArray) => {
+  return byteArray.reduce((str, byte) => str + byte.toString(16).padStart(2, "0"), "");
+};
+
+addEventListener("message", async ({ data: eventData }) => {
+  const { data, difficulty, threads } = eventData;
+  let nonce = eventData.nonce;
+  const isMainThread = nonce === 0;
+  let iterations = 0;
+
+  const requiredZeroBytes = Math.floor(difficulty / 2);
+  const isDifficultyOdd = difficulty % 2 !== 0;
+
+  for (; ;) {
+    const hashBuffer = await calculateSHA256(data + nonce);
+    const hashArray = new Uint8Array(hashBuffer);
+
+    let isValid = true;
+    for (let i = 0; i < requiredZeroBytes; i++) {
+      if (hashArray[i] !== 0) {
+        isValid = false;
+        break;
+      }
+    }
+
+    if (isValid && isDifficultyOdd) {
+      if ((hashArray[requiredZeroBytes] >> 4) !== 0) {
+        isValid = false;
+      }
+    }
+
+    if (isValid) {
+      const finalHash = toHexString(hashArray);
+      postMessage({
+        hash: finalHash,
+        data,
+        difficulty,
+        nonce,
+      });
+      return; // Exit worker
+    }
+
+    nonce += threads;
+    iterations++;
+
+    // Send a progress update from the main thread every 1024 iterations.
+    if (isMainThread && (iterations & 1023) === 0) {
+      postMessage(nonce);
+    }
+  }
+});