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>

.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

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
 

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/")

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",

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"
   }
-}
+}

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=${LICENSE}"
+for file in js/*.mjs js/worker/*.mjs; do
-gzip -f -k -n static/js/main.mjs
+  esbuild "${file}" --sourcemap --bundle --minify --outfile=static/"${file}" --banner:js="${LICENSE}"
-zstd -f -k --ultra -22 static/js/main.mjs
+  gzip -f -k -n static/${file}
-brotli -fZk static/js/main.mjs
+  zstd -f -k --ultra -22 static/${file}
-
+  brotli -fZk static/${file}
-esbuild js/bench.mjs --sourcemap --bundle --minify --outfile=static/js/bench.mjs
+done

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);
+    }
+  });
+}

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
+}

web/js/bench.mjs

@@ -1,11 +1,6 @@
-import processFast from "./proof-of-work.mjs";
+import algorithms from "./algorithms/index.mjs";
-import processSlow from "./proof-of-work-slow.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 });
 

web/js/main.mjs

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

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();
-}

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();
-}

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);
-    };
-  });
-};

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);
+    }
+  }
+});

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);
+    }
+  }
+});