initial draft

Makefile

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+
+release:
+	zip -r build.zip extension

README.md

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+# AudioContext Scrambler
+
+Protects you against AudioContext fingerprinting by adding random noise.
+
+## What is AudioContext Fingerprinting
+
+
+## Installation
+
+### From the store
+
+As any addons, navigate to its [store page](https://example.com) and click
+`Install`.
+
+### From releases
+
+1. Download the XPI file from Github Releases
+2. Navigate to about:addons
+3. Install Add-on from file
+4. Select the XPI file
+
+#### Build it myself
+
+Use `make release` to create the same XPI file as releases
+
+## Difference with the existing AudioContext Fingerprint Defender
+
+While the prupose is the same, this extension fixes several problems I had with
+AFD :
+- AFD inject code in the page as a script element
+- AFD then inject code in iframes if the document doesn't contain the attribute
+  `data-acxscriptallow`
+
+This extension uses `exportFunction`. This means that the DOM is not modified.
+Unlike AFD, this extension cannot be blocked by setting CSP to `unsafe-inline`
+or presetting `data-acxscriptallow` and using iframes.
+
+Finally, this extension has a Github repository so that everyone can participate
+and improve it.
+
+## Support
+
+This extension currently only support Firefox and Firefox for Android.
+
+## What's next?
+
+- Notify you when a page is trying to fingerprint you
+- Support Chromium
+- Configurable noise amplitude

extension/manifest.json

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+{
+
+  "manifest_version": 2,
+  "name": "AudioContext Scrambler",
+  "version": "1.0",
+
+  "description": "Scramble channel data to avoid AudioContext fingerprinting",
+
+  "content_scripts": [
+    {
+      "matches": ["*://*/*"],
+      "run_at": "document_start",
+      "js": ["scrambler.js"]
+    }
+  ]
+
+}

extension/scrambler.js

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+function createCustomChannelData(target) {
+  const original = target.prototype.getChannelData;
+  let buffer = null;
+  let getChannelData = function () {
+    const originalResult = original.apply(this, arguments);
+    if (buffer !== originalResult) {
+      buffer = originalResult;
+      for (var i = 0; i < originalResult.length; i += 100) {
+        let index = Math.floor(Math.random() * i);
+        originalResult[index] = originalResult[index] + Math.random() * 0.0000001;
+      }
+    }
+    return originalResult;
+  };
+  exportFunction(getChannelData, target.prototype, {defineAs:'getChannelData'});
+}
+
+function createCustomAnalyserNode(target) {
+  const original = target.prototype.getFloatFrequencyData;
+  let getFloatFrequencyData = function () {
+    const originalResult = original.apply(this, arguments);
+    for (var i = 0; i < arguments[0].length; i += 100) {
+      let index = Math.floor(Math.random() * i);
+      arguments[0][index] = arguments[0][index] + Math.random() * 0.1;
+    }
+    return originalResult;
+  };
+  exportFunction(getFloatFrequencyData, target.prototype, {defineAs:'getFloatFrequencyData'});
+}
+
+createCustomChannelData(window.AudioBuffer);
+createCustomChannelData(window.OfflineAudioContext);
+createCustomAnalyserNode(window.AnalyserNode);