diff --git a/build.js b/build.js
index b9ba69d..b768292 100644
--- a/build.js
+++ b/build.js
@@ -10,5 +10,5 @@ esbuild.buildSync({
   define: {
     global: "self",
   },
-  inject: ["process.js"],
+  inject: ["process.js", "polyfill.js"],
 });
diff --git a/package.json b/package.json
index 7057709..1f86f0d 100644
--- a/package.json
+++ b/package.json
@@ -15,6 +15,7 @@
     "dependencies": {
         "@lumeweb/hyperswarm-web": "git+https://git.lumeweb.com/LumeWeb/hyperswarm-web.git",
         "@noble/ed25519": "^1.7.3",
+        "@peculiar/webcrypto": "^1.4.3",
         "b4a": "^1.6.3",
         "eventemitter2": "^6.4.9",
         "hyperswarm": "^4.4.0",
diff --git a/polyfill.js b/polyfill.js
new file mode 100644
index 0000000..6767dc3
--- /dev/null
+++ b/polyfill.js
@@ -0,0 +1,11 @@
+import { Crypto } from "@peculiar/webcrypto";
+
+let globalCrypto = self.crypto;
+if (!globalCrypto.subtle) {
+  let subtleCrypto = new Crypto().subtle;
+  Object.defineProperty(globalCrypto, "subtle", {
+    get() {
+      return subtleCrypto;
+    },
+  });
+}