diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index a6a88353..cbac6a02 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -56,14 +56,15 @@ jobs:
       - run: flutter test --platform chrome
       - run: flutter test integration_test/webcrypto_test.dart -d macos
         working-directory: ./example
-      - uses: nanasess/setup-chromedriver@v2
-      - name: Run integration_test with chromedriver
-        working-directory: ./example
-        run: |
-          ../tool/with-chromedriver.sh flutter drive \
-            --driver=test_driver/integration_test.dart \
-            --target=integration_test/webcrypto_test.dart \
-            -d chrome
+      # TODO: Enable chromdriver testing on MacOS when it works reliably
+      #- uses: nanasess/setup-chromedriver@v2
+      #- name: Run integration_test with chromedriver
+      #  working-directory: ./example
+      #  run: |
+      #    ../tool/with-chromedriver.sh flutter drive \
+      #      --driver=test_driver/integration_test.dart \
+      #      --target=integration_test/webcrypto_test.dart \
+      #      -d chrome
       - run: flutter pub run test -p vm,chrome # TODO: Enable firefox if it works
   windows:
     name: webcrypto on Windows desktop / Chrome / Firefox
diff --git a/darwin/webcrypto.podspec b/darwin/webcrypto.podspec
index 13c9d766..14a1d006 100644
--- a/darwin/webcrypto.podspec
+++ b/darwin/webcrypto.podspec
@@ -28,7 +28,6 @@ Pod::Spec.new do |s|
   s.compiler_flags      = [
     '-DOPENSSL_NO_ASM',
     '-DDOPENSSL_SMALL',
-    '-GCC_WARN_INHIBIT_ALL_WARNINGS',
     '-w',
   ]
 
diff --git a/example/android/app/build.gradle b/example/android/app/build.gradle
index 0a9de12b..818d3854 100644
--- a/example/android/app/build.gradle
+++ b/example/android/app/build.gradle
@@ -1,3 +1,9 @@
+plugins {
+    id "com.android.application"
+    id "kotlin-android"
+    id "dev.flutter.flutter-gradle-plugin"
+}
+
 def localProperties = new Properties()
 def localPropertiesFile = rootProject.file('local.properties')
 if (localPropertiesFile.exists()) {
@@ -6,11 +12,6 @@ if (localPropertiesFile.exists()) {
     }
 }
 
-def flutterRoot = localProperties.getProperty('flutter.sdk')
-if (flutterRoot == null) {
-    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
-}
-
 def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
 if (flutterVersionCode == null) {
     flutterVersionCode = '1'
@@ -21,10 +22,6 @@ if (flutterVersionName == null) {
     flutterVersionName = '1.0'
 }
 
-apply plugin: 'com.android.application'
-apply plugin: 'kotlin-android'
-apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
-
 android {
     compileSdkVersion flutter.compileSdkVersion
     ndkVersion flutter.ndkVersion
@@ -66,5 +63,4 @@ flutter {
 }
 
 dependencies {
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
 }
diff --git a/example/android/build.gradle b/example/android/build.gradle
index 882fae21..bc157bd1 100644
--- a/example/android/build.gradle
+++ b/example/android/build.gradle
@@ -1,16 +1,3 @@
-buildscript {
-    ext.kotlin_version = '1.6.21'
-    repositories {
-        google()
-        mavenCentral()
-    }
-
-    dependencies {
-        classpath 'com.android.tools.build:gradle:8.4.1'
-        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
-    }
-}
-
 allprojects {
     repositories {
         google()
diff --git a/example/android/settings.gradle b/example/android/settings.gradle
index 44e62bcf..82990c39 100644
--- a/example/android/settings.gradle
+++ b/example/android/settings.gradle
@@ -1,11 +1,25 @@
-include ':app'
+pluginManagement {
+    def flutterSdkPath = {
+        def properties = new Properties()
+        file("local.properties").withInputStream { properties.load(it) }
+        def flutterSdkPath = properties.getProperty("flutter.sdk")
+        assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
+        return flutterSdkPath
+    }()
 
-def localPropertiesFile = new File(rootProject.projectDir, "local.properties")
-def properties = new Properties()
+    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
 
-assert localPropertiesFile.exists()
-localPropertiesFile.withReader("UTF-8") { reader -> properties.load(reader) }
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
 
-def flutterSdkPath = properties.getProperty("flutter.sdk")
-assert flutterSdkPath != null, "flutter.sdk not set in local.properties"
-apply from: "$flutterSdkPath/packages/flutter_tools/gradle/app_plugin_loader.gradle"
+plugins {
+    id "dev.flutter.flutter-plugin-loader" version "1.0.0"
+    id "com.android.application" version "8.4.1" apply false
+    id "org.jetbrains.kotlin.android" version "1.7.10" apply false
+}
+
+include ":app"
diff --git a/lib/src/impl_ffi/impl_ffi.aescbc.dart b/lib/src/impl_ffi/impl_ffi.aescbc.dart
index 34d9ae48..55a5e5a1 100644
--- a/lib/src/impl_ffi/impl_ffi.aescbc.dart
+++ b/lib/src/impl_ffi/impl_ffi.aescbc.dart
@@ -114,7 +114,7 @@ final class _StaticAesCbcSecretKeyImpl implements StaticAesCbcSecretKeyImpl {
   }
 }
 
-final class _AesCbcSecretKeyImpl extends AesCbcSecretKeyImpl {
+final class _AesCbcSecretKeyImpl implements AesCbcSecretKeyImpl {
   final Uint8List _key;
   _AesCbcSecretKeyImpl(this._key);
 
diff --git a/lib/src/impl_ffi/impl_ffi.aesctr.dart b/lib/src/impl_ffi/impl_ffi.aesctr.dart
index cfd8599f..709b5fff 100644
--- a/lib/src/impl_ffi/impl_ffi.aesctr.dart
+++ b/lib/src/impl_ffi/impl_ffi.aesctr.dart
@@ -221,7 +221,7 @@ final class _StaticAesCtrSecretKeyImpl implements StaticAesCtrSecretKeyImpl {
   }
 }
 
-final class _AesCtrSecretKeyImpl extends AesCtrSecretKeyImpl {
+final class _AesCtrSecretKeyImpl implements AesCtrSecretKeyImpl {
   final Uint8List _key;
   _AesCtrSecretKeyImpl(this._key);
 
diff --git a/lib/src/impl_ffi/impl_ffi.aesgcm.dart b/lib/src/impl_ffi/impl_ffi.aesgcm.dart
index 5adc463d..7922dd1a 100644
--- a/lib/src/impl_ffi/impl_ffi.aesgcm.dart
+++ b/lib/src/impl_ffi/impl_ffi.aesgcm.dart
@@ -16,19 +16,19 @@
 
 part of 'impl_ffi.dart';
 
-Future<AesGcmSecretKey> aesGcm_importRawKey(List<int> keyData) async =>
-    _AesGcmSecretKey(_aesImportRawKey(keyData));
+Future<AesGcmSecretKeyImpl> aesGcm_importRawKey(List<int> keyData) async =>
+    _AesGcmSecretKeyImpl(_aesImportRawKey(keyData));
 
-Future<AesGcmSecretKey> aesGcm_importJsonWebKey(
+Future<AesGcmSecretKeyImpl> aesGcm_importJsonWebKey(
   Map<String, dynamic> jwk,
 ) async =>
-    _AesGcmSecretKey(_aesImportJwkKey(
+    _AesGcmSecretKeyImpl(_aesImportJwkKey(
       jwk,
       expectedJwkAlgSuffix: 'GCM',
     ));
 
-Future<AesGcmSecretKey> aesGcm_generateKey(int length) async =>
-    _AesGcmSecretKey(_aesGenerateKey(length));
+Future<AesGcmSecretKeyImpl> aesGcm_generateKey(int length) async =>
+    _AesGcmSecretKeyImpl(_aesGenerateKey(length));
 
 Future<Uint8List> _aesGcmEncryptDecrypt(
   List<int> key,
@@ -111,9 +111,28 @@ Future<Uint8List> _aesGcmEncryptDecrypt(
   });
 }
 
-class _AesGcmSecretKey implements AesGcmSecretKey {
+final class _StaticAesGcmSecretKeyImpl implements StaticAesGcmSecretKeyImpl {
+  const _StaticAesGcmSecretKeyImpl();
+
+  @override
+  Future<AesGcmSecretKeyImpl> importRawKey(List<int> keyData) async {
+    return await aesGcm_importRawKey(keyData);
+  }
+
+  @override
+  Future<AesGcmSecretKeyImpl> importJsonWebKey(Map<String, dynamic> jwk) async {
+    return await aesGcm_importJsonWebKey(jwk);
+  }
+
+  @override
+  Future<AesGcmSecretKeyImpl> generateKey(int length) async {
+    return await aesGcm_generateKey(length);
+  }
+}
+
+final class _AesGcmSecretKeyImpl implements AesGcmSecretKeyImpl {
   final Uint8List _key;
-  _AesGcmSecretKey(this._key);
+  _AesGcmSecretKeyImpl(this._key);
 
   @override
   String toString() {
diff --git a/lib/src/impl_ffi/impl_ffi.dart b/lib/src/impl_ffi/impl_ffi.dart
index 85fd6ccf..591412a8 100644
--- a/lib/src/impl_ffi/impl_ffi.dart
+++ b/lib/src/impl_ffi/impl_ffi.dart
@@ -86,4 +86,13 @@ final class _WebCryptoImpl implements WebCryptoImpl {
 
   @override
   final ecdhPublicKey = const _StaticEcdhPublicKeyImpl();
+
+  @override
+  final aesGcmSecretKey = const _StaticAesGcmSecretKeyImpl();
+
+  @override
+  final hmacSecretKey = const _StaticHmacSecretKeyImpl();
+
+  @override
+  final pbkdf2SecretKey = const _StaticPbkdf2SecretKeyImpl();
 }
diff --git a/lib/src/impl_ffi/impl_ffi.hmac.dart b/lib/src/impl_ffi/impl_ffi.hmac.dart
index 72dfdbed..cb2d22f1 100644
--- a/lib/src/impl_ffi/impl_ffi.hmac.dart
+++ b/lib/src/impl_ffi/impl_ffi.hmac.dart
@@ -49,18 +49,18 @@ String _hmacJwkAlgFromHash(_Hash hash) {
   throw UnsupportedError('hash is not supported');
 }
 
-Future<HmacSecretKey> hmacSecretKey_importRawKey(
+Future<HmacSecretKeyImpl> hmacSecretKey_importRawKey(
   List<int> keyData,
   Hash hash, {
   int? length,
 }) async {
-  return _HmacSecretKey(
+  return _HmacSecretKeyImpl(
     _asUint8ListZeroedToBitLength(keyData, length),
     _Hash.fromHash(hash),
   );
 }
 
-Future<HmacSecretKey> hmacSecretKey_importJsonWebKey(
+Future<HmacSecretKeyImpl> hmacSecretKey_importJsonWebKey(
   Map<String, dynamic> jwk,
   Hash hash, {
   int? length,
@@ -86,7 +86,7 @@ Future<HmacSecretKey> hmacSecretKey_importJsonWebKey(
   return hmacSecretKey_importRawKey(keyData, hash, length: length);
 }
 
-Future<HmacSecretKey> hmacSecretKey_generateKey(
+Future<HmacSecretKeyImpl> hmacSecretKey_generateKey(
   Hash hash, {
   int? length,
 }) async {
@@ -95,25 +95,44 @@ Future<HmacSecretKey> hmacSecretKey_generateKey(
   final keyData = Uint8List((length / 8).ceil());
   fillRandomBytes(keyData);
 
-  return _HmacSecretKey(
+  return _HmacSecretKeyImpl(
     _asUint8ListZeroedToBitLength(keyData, length),
     h,
   );
 }
 
-class _HmacSecretKey implements HmacSecretKey {
+final class _StaticHmacSecretKeyImpl implements StaticHmacSecretKeyImpl {
+  const _StaticHmacSecretKeyImpl();
+
+  @override
+  Future<HmacSecretKeyImpl> importRawKey(List<int> keyData, Hash hash, {int? length}) {
+    return hmacSecretKey_importRawKey(keyData, hash, length: length);
+  }
+
+  @override
+  Future<HmacSecretKeyImpl> importJsonWebKey(Map<String, dynamic> jwk, Hash hash, {int? length}) {
+    return hmacSecretKey_importJsonWebKey(jwk, hash, length: length);
+  }
+
+  @override
+  Future<HmacSecretKeyImpl> generateKey(Hash hash, {int? length = 32}) {
+    return hmacSecretKey_generateKey(hash, length: length);
+  }
+}
+
+final class _HmacSecretKeyImpl implements HmacSecretKeyImpl {
   final _Hash _hash;
   final Uint8List _keyData;
 
-  _HmacSecretKey(this._keyData, this._hash);
+  _HmacSecretKeyImpl(this._keyData, this._hash);
 
   @override
   String toString() {
-    return 'Instance of \'HmacSecretKey\'';
+    return 'Instance of \'HmacSecretKeyImpl\'';
   }
 
   @override
-  Future<Uint8List> signBytes(List<int> data) => signStream(Stream.value(data));
+  Future<Uint8List>  signBytes(List<int> data) => signStream(Stream.value(data));
 
   @override
   Future<Uint8List> signStream(Stream<List<int>> data) {
diff --git a/lib/src/impl_ffi/impl_ffi.pbkdf2.dart b/lib/src/impl_ffi/impl_ffi.pbkdf2.dart
index 153eaa26..c9d4b16f 100644
--- a/lib/src/impl_ffi/impl_ffi.pbkdf2.dart
+++ b/lib/src/impl_ffi/impl_ffi.pbkdf2.dart
@@ -16,14 +16,23 @@
 
 part of 'impl_ffi.dart';
 
-Future<Pbkdf2SecretKey> pbkdf2SecretKey_importRawKey(List<int> keyData) async {
-  return _Pbkdf2SecretKey(Uint8List.fromList(keyData));
+Future<Pbkdf2SecretKeyImpl> pbkdf2SecretKey_importRawKey(List<int> keyData) async {
+  return _Pbkdf2SecretKeyImpl(Uint8List.fromList(keyData));
 }
 
-class _Pbkdf2SecretKey implements Pbkdf2SecretKey {
+final class _StaticPbkdf2SecretKeyImpl implements StaticPbkdf2SecretKeyImpl {
+  const _StaticPbkdf2SecretKeyImpl();
+
+  @override
+  Future<Pbkdf2SecretKeyImpl> importRawKey(List<int> keyData) {
+    return pbkdf2SecretKey_importRawKey(keyData);
+  }
+}
+
+final class _Pbkdf2SecretKeyImpl implements Pbkdf2SecretKeyImpl {
   final Uint8List _key;
 
-  _Pbkdf2SecretKey(this._key);
+  _Pbkdf2SecretKeyImpl(this._key);
 
   @override
   String toString() {
diff --git a/lib/src/impl_interface/impl_interface.aescbc.dart b/lib/src/impl_interface/impl_interface.aescbc.dart
index 47e5a382..543dc87d 100644
--- a/lib/src/impl_interface/impl_interface.aescbc.dart
+++ b/lib/src/impl_interface/impl_interface.aescbc.dart
@@ -20,7 +20,7 @@ abstract interface class StaticAesCbcSecretKeyImpl {
   Future<AesCbcSecretKeyImpl> generateKey(int length);
 }
 
-abstract class AesCbcSecretKeyImpl {
+abstract interface class AesCbcSecretKeyImpl {
   Future<Uint8List> encryptBytes(List<int> data, List<int> iv);
   Future<Uint8List> decryptBytes(List<int> data, List<int> iv);
   Stream<Uint8List> encryptStream(Stream<List<int>> data, List<int> iv);
diff --git a/lib/src/impl_interface/impl_interface.aesctr.dart b/lib/src/impl_interface/impl_interface.aesctr.dart
index 9714eecc..65db9dce 100644
--- a/lib/src/impl_interface/impl_interface.aesctr.dart
+++ b/lib/src/impl_interface/impl_interface.aesctr.dart
@@ -20,7 +20,7 @@ abstract interface class StaticAesCtrSecretKeyImpl {
   Future<AesCtrSecretKeyImpl> generateKey(int length);
 }
 
-abstract class AesCtrSecretKeyImpl {
+abstract interface class AesCtrSecretKeyImpl {
   Future<Uint8List> encryptBytes(List<int> data, List<int> counter, int length);
   Future<Uint8List> decryptBytes(List<int> data, List<int> counter, int length);
   Stream<Uint8List> encryptStream(Stream<List<int>> data, List<int> counter, int length);
diff --git a/lib/src/impl_interface/impl_interface.aesgcm.dart b/lib/src/impl_interface/impl_interface.aesgcm.dart
new file mode 100644
index 00000000..fa0afb88
--- /dev/null
+++ b/lib/src/impl_interface/impl_interface.aesgcm.dart
@@ -0,0 +1,28 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+part of 'impl_interface.dart';
+
+abstract interface class StaticAesGcmSecretKeyImpl {
+  Future<AesGcmSecretKeyImpl> importRawKey(List<int> keyData);
+  Future<AesGcmSecretKeyImpl> importJsonWebKey(Map<String, dynamic> jwk);
+  Future<AesGcmSecretKeyImpl> generateKey(int length);
+}
+
+abstract interface class AesGcmSecretKeyImpl {
+  Future<Uint8List> encryptBytes(List<int> data, List<int> iv, {List<int>? additionalData, int? tagLength});
+  Future<Uint8List> decryptBytes(List<int> data, List<int> iv, {List<int>? additionalData, int? tagLength});
+  Future<Uint8List> exportRawKey();
+  Future<Map<String, dynamic>> exportJsonWebKey();
+}
diff --git a/lib/src/impl_interface/impl_interface.dart b/lib/src/impl_interface/impl_interface.dart
index 51eeac51..d9e9f129 100644
--- a/lib/src/impl_interface/impl_interface.dart
+++ b/lib/src/impl_interface/impl_interface.dart
@@ -23,6 +23,14 @@ part 'impl_interface.aescbc.dart';
 part 'impl_interface.aesctr.dart';
 part 'impl_interface.ecdh.dart';
 
+import 'package:webcrypto/webcrypto.dart';
+
+
+part 'impl_interface.aescbc.dart';
+part 'impl_interface.aesctr.dart';
+part 'impl_interface.hmac.dart';
+part 'impl_interface.pbkdf2.dart';
+part 'impl_interface.aesgcm.dart';
 
 /// Interface to be provided by platform implementations.
 ///
@@ -45,4 +53,7 @@ abstract interface class WebCryptoImpl {
   StaticAesCtrSecretKeyImpl get aesCtrSecretKey;
   StaticEcdhPrivateKeyImpl get ecdhPrivateKey;
   StaticEcdhPublicKeyImpl get ecdhPublicKey;
+  StaticAesGcmSecretKeyImpl get aesGcmSecretKey;
+  StaticHmacSecretKeyImpl get hmacSecretKey;
+  StaticPbkdf2SecretKeyImpl get pbkdf2SecretKey;
 }
diff --git a/lib/src/impl_interface/impl_interface.hmac.dart b/lib/src/impl_interface/impl_interface.hmac.dart
new file mode 100644
index 00000000..ca12715c
--- /dev/null
+++ b/lib/src/impl_interface/impl_interface.hmac.dart
@@ -0,0 +1,30 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+part of 'impl_interface.dart';
+
+abstract interface class StaticHmacSecretKeyImpl {
+  Future<HmacSecretKeyImpl> importRawKey(List<int> keyData, Hash hash, {int? length});
+  Future<HmacSecretKeyImpl> importJsonWebKey(Map<String, dynamic> jwk, Hash hash, {int? length});
+  Future<HmacSecretKeyImpl> generateKey(Hash hash, {int? length});
+}
+
+abstract interface class HmacSecretKeyImpl {
+  Future<Uint8List> signBytes(List<int> data);
+  Future<bool> verifyBytes(List<int> signature, List<int> data);
+  Future<Uint8List> signStream(Stream<List<int>> data);
+  Future<bool> verifyStream(List<int> signature, Stream<List<int>> data);
+  Future<Uint8List> exportRawKey();
+  Future<Map<String, dynamic>> exportJsonWebKey();
+}
diff --git a/lib/src/impl_interface/impl_interface.pbkdf2.dart b/lib/src/impl_interface/impl_interface.pbkdf2.dart
new file mode 100644
index 00000000..26f1d1ea
--- /dev/null
+++ b/lib/src/impl_interface/impl_interface.pbkdf2.dart
@@ -0,0 +1,23 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+part of 'impl_interface.dart';
+
+abstract interface class StaticPbkdf2SecretKeyImpl {
+  Future<Pbkdf2SecretKeyImpl> importRawKey(List<int> keyData);
+}
+
+abstract interface class Pbkdf2SecretKeyImpl {
+  Future<Uint8List> deriveBits(int length, Hash hash, List<int> salt, int iterations);
+}
diff --git a/lib/src/impl_js/impl_js.aesctr.dart b/lib/src/impl_js/impl_js.aesctr.dart
index 895701f5..3a97ff80 100644
--- a/lib/src/impl_js/impl_js.aesctr.dart
+++ b/lib/src/impl_js/impl_js.aesctr.dart
@@ -66,7 +66,7 @@ final class _StaticAesCtrSecretKeyImpl implements StaticAesCtrSecretKeyImpl {
   }
 }
 
-final class _AesCtrSecretKeyImpl extends AesCtrSecretKeyImpl {
+final class _AesCtrSecretKeyImpl implements AesCtrSecretKeyImpl {
   final subtle.JSCryptoKey _key;
   _AesCtrSecretKeyImpl(this._key);
 
diff --git a/lib/src/impl_js/impl_js.aesgcm.dart b/lib/src/impl_js/impl_js.aesgcm.dart
index d1dae77b..d630e15a 100644
--- a/lib/src/impl_js/impl_js.aesgcm.dart
+++ b/lib/src/impl_js/impl_js.aesgcm.dart
@@ -18,8 +18,8 @@ part of 'impl_js.dart';
 
 const _aesGcmAlgorithm = subtle.Algorithm(name: 'AES-GCM');
 
-Future<AesGcmSecretKey> aesGcm_importRawKey(List<int> keyData) async {
-  return _AesGcmSecretKey(await _importKey(
+Future<AesGcmSecretKeyImpl> aesGcm_importRawKey(List<int> keyData) async {
+  return _AesGcmSecretKeyImpl(await _importKey(
     'raw',
     keyData,
     _aesGcmAlgorithm,
@@ -28,10 +28,10 @@ Future<AesGcmSecretKey> aesGcm_importRawKey(List<int> keyData) async {
   ));
 }
 
-Future<AesGcmSecretKey> aesGcm_importJsonWebKey(
+Future<AesGcmSecretKeyImpl> aesGcm_importJsonWebKey(
   Map<String, dynamic> jwk,
 ) async {
-  return _AesGcmSecretKey(await _importJsonWebKey(
+  return _AesGcmSecretKeyImpl(await _importJsonWebKey(
     jwk,
     _aesGcmAlgorithm,
     _usagesEncryptDecrypt,
@@ -39,17 +39,36 @@ Future<AesGcmSecretKey> aesGcm_importJsonWebKey(
   ));
 }
 
-Future<AesGcmSecretKey> aesGcm_generateKey(int length) async {
-  return _AesGcmSecretKey(await _generateKey(
+Future<AesGcmSecretKeyImpl> aesGcm_generateKey(int length) async {
+  return _AesGcmSecretKeyImpl(await _generateKey(
     _aesGcmAlgorithm.update(length: length),
     _usagesEncryptDecrypt,
     'secret',
   ));
 }
 
-class _AesGcmSecretKey implements AesGcmSecretKey {
+final class _StaticAesGcmSecretKeyImpl implements StaticAesGcmSecretKeyImpl {
+  const _StaticAesGcmSecretKeyImpl();
+
+  @override
+  Future<AesGcmSecretKeyImpl> importRawKey(List<int> keyData) async {
+    return await aesGcm_importRawKey(keyData);
+  }
+
+  @override
+  Future<AesGcmSecretKeyImpl> importJsonWebKey(Map<String, dynamic> jwk) async {
+    return await aesGcm_importJsonWebKey(jwk);
+  }
+
+  @override
+  Future<AesGcmSecretKeyImpl> generateKey(int length) async {
+    return await aesGcm_generateKey(length);
+  }
+}
+
+final class _AesGcmSecretKeyImpl implements AesGcmSecretKeyImpl {
   final subtle.JSCryptoKey _key;
-  _AesGcmSecretKey(this._key);
+  _AesGcmSecretKeyImpl(this._key);
 
   @override
   String toString() {
diff --git a/lib/src/impl_js/impl_js.dart b/lib/src/impl_js/impl_js.dart
index 042b4921..97a955d6 100644
--- a/lib/src/impl_js/impl_js.dart
+++ b/lib/src/impl_js/impl_js.dart
@@ -72,4 +72,13 @@ final class _WebCryptoImpl implements WebCryptoImpl {
 
   @override
   final ecdhPublicKey = const _StaticEcdhPublicKeyImpl();
+  
+  @override
+  final aesGcmSecretKey = const _StaticAesGcmSecretKeyImpl();
+
+  @override
+  final hmacSecretKey = const _StaticHmacSecretKeyImpl();
+
+  @override
+  final pbkdf2SecretKey = const _StaticPbkdf2SecretKeyImpl();
 }
diff --git a/lib/src/impl_js/impl_js.hmac.dart b/lib/src/impl_js/impl_js.hmac.dart
index 7857a71c..d3403728 100644
--- a/lib/src/impl_js/impl_js.hmac.dart
+++ b/lib/src/impl_js/impl_js.hmac.dart
@@ -18,12 +18,12 @@ part of 'impl_js.dart';
 
 const _hmacAlgorithm = subtle.Algorithm(name: 'HMAC');
 
-Future<HmacSecretKey> hmacSecretKey_importRawKey(
+Future<HmacSecretKeyImpl> hmacSecretKey_importRawKey(
   List<int> keyData,
   Hash hash, {
   int? length,
 }) async {
-  return _HmacSecretKey(await _importKey(
+  return _HmacSecretKeyImpl(await _importKey(
     'raw',
     keyData,
     length == null
@@ -41,12 +41,12 @@ Future<HmacSecretKey> hmacSecretKey_importRawKey(
   ));
 }
 
-Future<HmacSecretKey> hmacSecretKey_importJsonWebKey(
+Future<HmacSecretKeyImpl> hmacSecretKey_importJsonWebKey(
   Map<String, dynamic> jwk,
   Hash hash, {
   int? length,
 }) async {
-  return _HmacSecretKey(await _importJsonWebKey(
+  return _HmacSecretKeyImpl(await _importJsonWebKey(
     jwk,
     length == null
         ? subtle.Algorithm(
@@ -63,9 +63,9 @@ Future<HmacSecretKey> hmacSecretKey_importJsonWebKey(
   ));
 }
 
-Future<HmacSecretKey> hmacSecretKey_generateKey(Hash hash,
+Future<HmacSecretKeyImpl> hmacSecretKey_generateKey(Hash hash,
     {int? length}) async {
-  return _HmacSecretKey(await _generateKey(
+  return _HmacSecretKeyImpl(await _generateKey(
     length == null
         ? subtle.Algorithm(
             name: 'HMAC',
@@ -81,9 +81,30 @@ Future<HmacSecretKey> hmacSecretKey_generateKey(Hash hash,
   ));
 }
 
-class _HmacSecretKey implements HmacSecretKey {
+final class _StaticHmacSecretKeyImpl implements StaticHmacSecretKeyImpl {
+  const _StaticHmacSecretKeyImpl();
+
+  @override
+  Future<HmacSecretKeyImpl> importRawKey(List<int> keyData, Hash hash,
+      {int? length}) {
+    return hmacSecretKey_importRawKey(keyData, hash, length: length);
+  }
+
+  @override
+  Future<HmacSecretKeyImpl> importJsonWebKey(Map<String, dynamic> jwk, Hash hash,
+      {int? length}) {
+    return hmacSecretKey_importJsonWebKey(jwk, hash, length: length);
+  }
+
+  @override
+  Future<HmacSecretKeyImpl> generateKey(Hash hash, {int? length = 32}) {
+    return hmacSecretKey_generateKey(hash, length: length);
+  }
+}
+
+final class _HmacSecretKeyImpl implements HmacSecretKeyImpl {
   final subtle.JSCryptoKey _key;
-  _HmacSecretKey(this._key);
+  _HmacSecretKeyImpl(this._key);
 
   @override
   String toString() {
diff --git a/lib/src/impl_js/impl_js.pbkdf2.dart b/lib/src/impl_js/impl_js.pbkdf2.dart
index b8479971..8f72f857 100644
--- a/lib/src/impl_js/impl_js.pbkdf2.dart
+++ b/lib/src/impl_js/impl_js.pbkdf2.dart
@@ -18,8 +18,8 @@ part of 'impl_js.dart';
 
 const _pbkdf2AlgorithmName = 'PBKDF2';
 
-Future<Pbkdf2SecretKey> pbkdf2SecretKey_importRawKey(List<int> keyData) async {
-  return _Pbkdf2SecretKey(await _importKey(
+Future<Pbkdf2SecretKeyImpl> pbkdf2SecretKey_importRawKey(List<int> keyData) async {
+  return _Pbkdf2SecretKeyImpl(await _importKey(
     'raw',
     keyData,
     const subtle.Algorithm(name: _pbkdf2AlgorithmName),
@@ -31,9 +31,18 @@ Future<Pbkdf2SecretKey> pbkdf2SecretKey_importRawKey(List<int> keyData) async {
   ));
 }
 
-class _Pbkdf2SecretKey implements Pbkdf2SecretKey {
+final class _StaticPbkdf2SecretKeyImpl implements StaticPbkdf2SecretKeyImpl {
+  const _StaticPbkdf2SecretKeyImpl();
+
+  @override
+  Future<Pbkdf2SecretKeyImpl> importRawKey(List<int> keyData) {
+    return pbkdf2SecretKey_importRawKey(keyData);
+  }
+}
+
+final class _Pbkdf2SecretKeyImpl implements Pbkdf2SecretKeyImpl {
   final subtle.JSCryptoKey _key;
-  _Pbkdf2SecretKey(this._key);
+  _Pbkdf2SecretKeyImpl(this._key);
 
   @override
   String toString() {
diff --git a/lib/src/impl_stub.dart b/lib/src/impl_stub.dart
index 475e8210..b12c0882 100644
--- a/lib/src/impl_stub.dart
+++ b/lib/src/impl_stub.dart
@@ -45,23 +45,6 @@ const Hash sha256 = _UnimplementedHash();
 const Hash sha384 = _UnimplementedHash();
 const Hash sha512 = _UnimplementedHash();
 
-//---------------------- HMAC
-Future<HmacSecretKey> hmacSecretKey_importRawKey(
-  List<int> keyData,
-  Hash hash, {
-  int? length,
-}) =>
-    throw _notImplemented;
-
-Future<HmacSecretKey> hmacSecretKey_importJsonWebKey(
-  Map<String, dynamic> jwk,
-  Hash hash, {
-  int? length,
-}) =>
-    throw _notImplemented;
-
-Future<HmacSecretKey> hmacSecretKey_generateKey(Hash hash, {int? length}) =>
-    throw _notImplemented;
 
 //---------------------- RSASSA_PKCS1_v1_5
 
@@ -207,14 +190,6 @@ Future<RsaOaepPublicKey> rsaOaepPublicKey_importJsonWebKey(
 
 //---------------------- AES-GCM
 
-Future<AesGcmSecretKey> aesGcm_importRawKey(List<int> keyData) =>
-    throw _notImplemented;
-
-Future<AesGcmSecretKey> aesGcm_importJsonWebKey(Map<String, dynamic> jwk) =>
-    throw _notImplemented;
-
-Future<AesGcmSecretKey> aesGcm_generateKey(int length) => throw _notImplemented;
-
 //---------------------- ECDH
 
 //---------------------- HKDF
@@ -224,5 +199,3 @@ Future<HkdfSecretKey> hkdfSecretKey_importRawKey(List<int> keyData) =>
 
 //---------------------- PBKDF2
 
-Future<Pbkdf2SecretKey> pbkdf2SecretKey_importRawKey(List<int> keyData) =>
-    throw _notImplemented;
diff --git a/lib/src/impl_stub/impl_stub.aesgcm.dart b/lib/src/impl_stub/impl_stub.aesgcm.dart
new file mode 100644
index 00000000..7f98490e
--- /dev/null
+++ b/lib/src/impl_stub/impl_stub.aesgcm.dart
@@ -0,0 +1,31 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+part of 'impl_stub.dart';
+
+final class _StaticAesGcmSecretKeyImpl implements StaticAesGcmSecretKeyImpl {
+  const _StaticAesGcmSecretKeyImpl();
+
+  @override
+  Future<AesGcmSecretKeyImpl> importRawKey(List<int> keyData) =>
+    throw UnimplementedError('Not implemented');
+
+  @override
+  Future<AesGcmSecretKeyImpl> importJsonWebKey(Map<String, dynamic> jwk) =>
+    throw UnimplementedError('Not implemented');
+
+  @override
+  Future<AesGcmSecretKeyImpl> generateKey(int length) =>
+    throw UnimplementedError('Not implemented');
+}
diff --git a/lib/src/impl_stub/impl_stub.dart b/lib/src/impl_stub/impl_stub.dart
index 7b043ecb..515f57b0 100644
--- a/lib/src/impl_stub/impl_stub.dart
+++ b/lib/src/impl_stub/impl_stub.dart
@@ -15,11 +15,14 @@
 library webcrypto.impl_stub;
 
 import 'package:webcrypto/src/impl_interface/impl_interface.dart';
-import '../webcrypto/webcrypto.dart';
+import 'package:webcrypto/webcrypto.dart';
 
 part 'impl_stub.aescbc.dart';
 part 'impl_stub.aesctr.dart';
+part 'impl_stub.aesgcm.dart';
 part 'impl_stub.ecdh.dart';
+part 'impl_stub.hmac.dart';
+part 'impl_stub.pbkdf2.dart';
 
 const WebCryptoImpl webCryptImpl = _WebCryptoImpl();
 
@@ -37,4 +40,13 @@ final class _WebCryptoImpl implements WebCryptoImpl {
 
   @override
   final ecdhPublicKey = const _StaticEcdhPublicKeyImpl();
+
+  @override
+  final aesGcmSecretKey = const _StaticAesGcmSecretKeyImpl();
+
+  @override
+  final hmacSecretKey = const _StaticHmacSecretKeyImpl();
+
+  @override
+  final pbkdf2SecretKey = const _StaticPbkdf2SecretKeyImpl();
 }
diff --git a/lib/src/impl_stub/impl_stub.hmac.dart b/lib/src/impl_stub/impl_stub.hmac.dart
new file mode 100644
index 00000000..c5deb07d
--- /dev/null
+++ b/lib/src/impl_stub/impl_stub.hmac.dart
@@ -0,0 +1,34 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+part of 'impl_stub.dart';
+
+final class _StaticHmacSecretKeyImpl implements StaticHmacSecretKeyImpl {
+  const _StaticHmacSecretKeyImpl();
+
+  @override
+  Future<HmacSecretKeyImpl> importRawKey(List<int> keyData, Hash hash, {int? length}) {
+    throw UnimplementedError('Not implemented');
+  }
+
+  @override
+  Future<HmacSecretKeyImpl> importJsonWebKey(Map<String, dynamic> jwk, Hash hash, {int? length}) {
+    throw UnimplementedError('Not implemented');
+  }
+
+  @override
+  Future<HmacSecretKeyImpl> generateKey(Hash hash, {int? length = 32}) {
+    throw UnimplementedError('Not implemented');
+  }
+}
diff --git a/lib/src/impl_stub/impl_stub.pbkdf2.dart b/lib/src/impl_stub/impl_stub.pbkdf2.dart
new file mode 100644
index 00000000..e1fc586f
--- /dev/null
+++ b/lib/src/impl_stub/impl_stub.pbkdf2.dart
@@ -0,0 +1,24 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+part of 'impl_stub.dart';
+
+final class _StaticPbkdf2SecretKeyImpl implements StaticPbkdf2SecretKeyImpl {
+  const _StaticPbkdf2SecretKeyImpl();
+
+  @override
+  Future<Pbkdf2SecretKeyImpl> importRawKey(List<int> keyData) {
+    throw UnimplementedError('Not implemented');
+  }
+}
diff --git a/lib/src/webcrypto/webcrypto.aesgcm.dart b/lib/src/webcrypto/webcrypto.aesgcm.dart
index c27f09b1..f5acbf53 100644
--- a/lib/src/webcrypto/webcrypto.aesgcm.dart
+++ b/lib/src/webcrypto/webcrypto.aesgcm.dart
@@ -32,9 +32,10 @@ part of 'webcrypto.dart';
 /// [1]: https://csrc.nist.gov/pubs/sp/800/38/d/final
 /// [2]: https://tools.ietf.org/html/rfc7517
 /// [3]: https://en.wikipedia.org/wiki/Authenticated_encryption
-@sealed
-abstract class AesGcmSecretKey {
-  AesGcmSecretKey._(); // keep the constructor private.
+final class AesGcmSecretKey {
+  final AesGcmSecretKeyImpl _impl;
+
+  AesGcmSecretKey._(this._impl); // keep the constructor private.
 
   /// Import an [AesGcmSecretKey] from raw [keyData].
   ///
@@ -66,8 +67,9 @@ abstract class AesGcmSecretKey {
   /// // Decrypt message (requires the same iv)
   /// print(utf8.decode(await k.decryptBytes(c, iv))); // hello world
   /// ```
-  static Future<AesGcmSecretKey> importRawKey(List<int> keyData) {
-    return impl.aesGcm_importRawKey(keyData);
+  static Future<AesGcmSecretKey> importRawKey(List<int> keyData) async {
+    final impl = await webCryptImpl.aesGcmSecretKey.importRawKey(keyData);
+    return AesGcmSecretKey._(impl);
   }
 
   /// Import an [AesGcmSecretKey] from [JSON Web Key][1].
@@ -102,8 +104,9 @@ abstract class AesGcmSecretKey {
   /// ```
   ///
   /// [1]: https://tools.ietf.org/html/rfc7517
-  static Future<AesGcmSecretKey> importJsonWebKey(Map<String, dynamic> jwk) {
-    return impl.aesGcm_importJsonWebKey(jwk);
+  static Future<AesGcmSecretKey> importJsonWebKey(Map<String, dynamic> jwk) async {
+    final impl = await webCryptImpl.aesGcmSecretKey.importJsonWebKey(jwk);
+    return AesGcmSecretKey._(impl);
   }
 
   /// Generate a random [AesGcmSecretKey].
@@ -122,8 +125,9 @@ abstract class AesGcmSecretKey {
   /// // Generate a new random AES-GCM secret key for AES-256.
   /// final key = await AesGcmSecretKey.generate(256);
   /// ```
-  static Future<AesGcmSecretKey> generateKey(int length) {
-    return impl.aesGcm_generateKey(length);
+  static Future<AesGcmSecretKey> generateKey(int length) async {
+    final impl = await webCryptImpl.aesGcmSecretKey.generateKey(length);
+    return AesGcmSecretKey._(impl);
   }
 
   /// Encrypt [data] with this [AesCbcSecretKey] using AES in
@@ -218,7 +222,8 @@ abstract class AesGcmSecretKey {
     List<int> iv, {
     List<int>? additionalData,
     int? tagLength = 128,
-  });
+  }) =>
+      _impl.encryptBytes(data, iv, additionalData: additionalData, tagLength: tagLength);
 
   // TODO: Document this method, notice that [data] must be concatenation of
   //       ciphertext and authentication tag.
@@ -228,7 +233,8 @@ abstract class AesGcmSecretKey {
     List<int> iv, {
     List<int>? additionalData,
     int? tagLength = 128,
-  });
+  }) =>
+      _impl.decryptBytes(data, iv, additionalData: additionalData, tagLength: tagLength);
 
   /// Export [AesGcmSecretKey] as raw bytes.
   ///
@@ -250,7 +256,7 @@ abstract class AesGcmSecretKey {
   /// // If we wanted to we could import the key as follows:
   /// // key = await AesGcmSecretKey.importRawKey(secretBytes);
   /// ```
-  Future<Uint8List> exportRawKey();
+  Future<Uint8List> exportRawKey() => _impl.exportRawKey();
 
   /// Export [AesGcmSecretKey] as [JSON Web Key][1].
   ///
@@ -274,5 +280,5 @@ abstract class AesGcmSecretKey {
   /// ```
   ///
   /// [1]: https://tools.ietf.org/html/rfc7517
-  Future<Map<String, dynamic>> exportJsonWebKey();
+  Future<Map<String, dynamic>> exportJsonWebKey() => _impl.exportJsonWebKey();
 }
diff --git a/lib/src/webcrypto/webcrypto.hmac.dart b/lib/src/webcrypto/webcrypto.hmac.dart
index 04b046bd..e5256754 100644
--- a/lib/src/webcrypto/webcrypto.hmac.dart
+++ b/lib/src/webcrypto/webcrypto.hmac.dart
@@ -48,9 +48,10 @@ part of 'webcrypto.dart';
 /// ```
 /// 
 /// [1]: https://doi.org/10.6028/NIST.FIPS.180-4
-@sealed
-abstract class HmacSecretKey {
-  HmacSecretKey._(); // keep the constructor private.
+final class HmacSecretKey {
+  final HmacSecretKeyImpl _impl;
+
+  HmacSecretKey._(this._impl); // keep the constructor private.
 
   /// Import [HmacSecretKey] from raw [keyData].
   ///
@@ -76,7 +77,7 @@ abstract class HmacSecretKey {
     List<int> keyData,
     Hash hash, {
     int? length,
-  }) {
+  }) async {
     // These limitations are given in Web Cryptography Spec:
     // https://www.w3.org/TR/WebCryptoAPI/#hmac-operations
     if (length != null && length > keyData.length * 8) {
@@ -92,7 +93,13 @@ abstract class HmacSecretKey {
       );
     }
 
-    return impl.hmacSecretKey_importRawKey(keyData, hash, length: length);
+    final impl = await webCryptImpl.hmacSecretKey.importRawKey(
+      keyData,
+      hash,
+      length: length,
+    );
+
+    return HmacSecretKey._(impl);
   }
 
   /// Import [HmacSecretKey] from [JSON Web Key][1].
@@ -147,7 +154,7 @@ abstract class HmacSecretKey {
     //       Note. it's not yet clear if JWK always contains key parameters.
     Hash hash, {
     int? length,
-  }) {
+  }) async {
     /*
     TODO: Validate these in the native implememtation
     // These limitations are given in Web Cryptography Spec:
@@ -165,7 +172,9 @@ abstract class HmacSecretKey {
       );
     }*/
 
-    return impl.hmacSecretKey_importJsonWebKey(jwk, hash, length: length);
+    final impl = await webCryptImpl.hmacSecretKey.importJsonWebKey(jwk, hash);
+
+    return HmacSecretKey._(impl);
   }
 
   /// Generate random [HmacSecretKey].
@@ -181,12 +190,14 @@ abstract class HmacSecretKey {
   /// // Generate a new random HMAC secret key.
   /// final key = await HmacSecretKey.generate(Hash.sha256);
   /// ```
-  static Future<HmacSecretKey> generateKey(Hash hash, {int? length}) {
+  static Future<HmacSecretKey> generateKey(Hash hash, {int? length}) async {
     if (length != null && length <= 0) {
       throw ArgumentError.value(length, 'length', 'must be positive');
     }
 
-    return impl.hmacSecretKey_generateKey(hash, length: length);
+    final impl = await webCryptImpl.hmacSecretKey.generateKey(hash, length: length);
+
+    return HmacSecretKey._(impl);
   }
 
   /// Compute an HMAC signature of given [data].
@@ -219,7 +230,7 @@ abstract class HmacSecretKey {
   /// instead, these methods computes a signature and does a
   /// fixed-time comparison.
   /// {@endtemplate}
-  Future<Uint8List> signBytes(List<int> data);
+  Future<Uint8List> signBytes(List<int> data) async => await _impl.signBytes(data);
 
   /// Compute an HMAC signature of given [data] stream.
   ///
@@ -246,7 +257,8 @@ abstract class HmacSecretKey {
   /// ```
   ///
   /// {@macro HMAC-sign:do-not-validate-using-sign}
-  Future<Uint8List> signStream(Stream<List<int>> data);
+  Future<Uint8List> signStream(Stream<List<int>> data) =>
+    _impl.signStream(data);
 
   /// Verify the HMAC [signature] of given [data].
   ///
@@ -282,7 +294,8 @@ abstract class HmacSecretKey {
   /// );
   /// assert(result == true, 'this signature should be valid');
   /// ```
-  Future<bool> verifyBytes(List<int> signature, List<int> data);
+  Future<bool> verifyBytes(List<int> signature, List<int> data) =>
+    _impl.verifyBytes(signature, data);
 
   /// Verify the HMAC [signature] of given [data] stream.
   ///
@@ -313,7 +326,8 @@ abstract class HmacSecretKey {
   /// ]));
   /// assert(result == true, 'this signature should be valid');
   /// ```
-  Future<bool> verifyStream(List<int> signature, Stream<List<int>> data);
+  Future<bool> verifyStream(List<int> signature, Stream<List<int>> data) =>
+    _impl.verifyStream(signature, data);
 
   /// Export [HmacSecretKey] as raw bytes.
   ///
@@ -336,7 +350,7 @@ abstract class HmacSecretKey {
   /// // If we wanted to we could import the key as follows:
   /// // key = await HmacSecretKey.importRawKey(secretBytes, Hash.sha256);
   /// ```
-  Future<Uint8List> exportRawKey();
+  Future<Uint8List> exportRawKey() => _impl.exportRawKey();
 
   /// Export [HmacSecretKey] as [JSON Web Key][1].
   ///
@@ -360,5 +374,5 @@ abstract class HmacSecretKey {
   /// ```
   ///
   /// [1]: https://tools.ietf.org/html/rfc7517
-  Future<Map<String, dynamic>> exportJsonWebKey();
+  Future<Map<String, dynamic>> exportJsonWebKey() => _impl.exportJsonWebKey();
 }
diff --git a/lib/src/webcrypto/webcrypto.pbkdf2.dart b/lib/src/webcrypto/webcrypto.pbkdf2.dart
index 4c6892bf..f35fc5ee 100644
--- a/lib/src/webcrypto/webcrypto.pbkdf2.dart
+++ b/lib/src/webcrypto/webcrypto.pbkdf2.dart
@@ -50,17 +50,20 @@ part of 'webcrypto.dart';
 ///
 /// [1]: https://tools.ietf.org/html/rfc8018
 // TODO: Rewrite all RFC links to use https://www.rfc-editor.org/rfc/rfcXXXX
-@sealed
-abstract class Pbkdf2SecretKey {
-  Pbkdf2SecretKey._(); // keep the constructor private.
+
+final class Pbkdf2SecretKey {
+  final Pbkdf2SecretKeyImpl _impl;
+  
+  Pbkdf2SecretKey._(this._impl); // keep the constructor private.
 
   /// Import [Pbkdf2SecretKey] from raw [keyData].
   ///
   /// Creates a [Pbkdf2SecretKey] for key derivation using [keyData].
   ///
   /// {@macro Pbkdf2SecretKey:example}
-  static Future<Pbkdf2SecretKey> importRawKey(List<int> keyData) {
-    return impl.pbkdf2SecretKey_importRawKey(keyData);
+  static Future<Pbkdf2SecretKey> importRawKey(List<int> keyData) async {
+    final impl = await webCryptImpl.pbkdf2SecretKey.importRawKey(keyData);
+    return Pbkdf2SecretKey._(impl);
   }
 
   /// Derive key from [salt] and password specified as `keyData` in
@@ -90,5 +93,6 @@ abstract class Pbkdf2SecretKey {
     Hash hash,
     List<int> salt,
     int iterations,
-  );
+  ) =>
+    _impl.deriveBits(length, hash, salt, iterations);
 }