diff --git a/quartz/src/appleMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.apple.kt b/quartz/src/appleMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.apple.kt
index eb065059a..9536b80e5 100644
--- a/quartz/src/appleMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.apple.kt
+++ b/quartz/src/appleMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.apple.kt
@@ -63,4 +63,22 @@ actual class AESGCM actual constructor(
             Log.w("AESGCM", "Failed to decrypt", e)
             null
         }
+
+    @OptIn(DelicateCryptographyApi::class)
+    actual fun encrypt(
+        bytesToEncrypt: ByteArray,
+        aad: ByteArray,
+    ): ByteArray =
+        with(cipher()) {
+            encryptWithIvBlocking(nonce, bytesToEncrypt, aad)
+        }
+
+    @OptIn(DelicateCryptographyApi::class)
+    actual fun decrypt(
+        bytesToDecrypt: ByteArray,
+        aad: ByteArray,
+    ): ByteArray =
+        with(cipher()) {
+            decryptWithIvBlocking(nonce, bytesToDecrypt, aad)
+        }
 }
diff --git a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mls/crypto/Hpke.kt b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mls/crypto/Hpke.kt
index 23d328d97..67508522d 100644
--- a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mls/crypto/Hpke.kt
+++ b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mls/crypto/Hpke.kt
@@ -197,20 +197,12 @@ object Hpke {
         nonce: ByteArray,
         aad: ByteArray,
         plaintext: ByteArray,
-    ): ByteArray {
-        val cipher = AESGCM(key, nonce)
-        // Note: Current AESGCM doesn't support AAD. For HPKE base mode with empty AAD this works.
-        // TODO: Add AAD support to AESGCM for full compliance
-        return cipher.encrypt(plaintext)
-    }
+    ): ByteArray = AESGCM(key, nonce).encrypt(plaintext, aad)
 
     private fun aeadOpen(
         key: ByteArray,
         nonce: ByteArray,
         aad: ByteArray,
         ciphertext: ByteArray,
-    ): ByteArray {
-        val cipher = AESGCM(key, nonce)
-        return cipher.decrypt(ciphertext)
-    }
+    ): ByteArray = AESGCM(key, nonce).decrypt(ciphertext, aad)
 }
diff --git a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mls/crypto/MlsCryptoProvider.kt b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mls/crypto/MlsCryptoProvider.kt
index 2d22a54ef..c2eca8b0f 100644
--- a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mls/crypto/MlsCryptoProvider.kt
+++ b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/marmot/mls/crypto/MlsCryptoProvider.kt
@@ -139,22 +139,14 @@ object MlsCryptoProvider {
         nonce: ByteArray,
         aad: ByteArray,
         plaintext: ByteArray,
-    ): ByteArray {
-        val cipher = AESGCM(key, nonce)
-        // AESGCM doesn't support AAD directly; for MLS we need raw AES-GCM with AAD
-        // TODO: extend AESGCM to support AAD or use platform-specific AES-GCM with AAD
-        return cipher.encrypt(plaintext)
-    }
+    ): ByteArray = AESGCM(key, nonce).encrypt(plaintext, aad)
 
     fun aeadDecrypt(
         key: ByteArray,
         nonce: ByteArray,
         aad: ByteArray,
         ciphertext: ByteArray,
-    ): ByteArray {
-        val cipher = AESGCM(key, nonce)
-        return cipher.decrypt(ciphertext)
-    }
+    ): ByteArray = AESGCM(key, nonce).decrypt(ciphertext, aad)
 
     // --- Random ---
 
diff --git a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.kt b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.kt
index 8b1b00578..831100a90 100644
--- a/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.kt
+++ b/quartz/src/commonMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.kt
@@ -36,4 +36,16 @@ expect class AESGCM(
     override fun decrypt(bytesToDecrypt: ByteArray): ByteArray
 
     override fun decryptOrNull(bytesToDecrypt: ByteArray): ByteArray?
+
+    /** AES-GCM encrypt with Additional Authenticated Data (AAD). */
+    fun encrypt(
+        bytesToEncrypt: ByteArray,
+        aad: ByteArray,
+    ): ByteArray
+
+    /** AES-GCM decrypt with Additional Authenticated Data (AAD). */
+    fun decrypt(
+        bytesToDecrypt: ByteArray,
+        aad: ByteArray,
+    ): ByteArray
 }
diff --git a/quartz/src/jvmAndroid/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.jvmAndroid.kt b/quartz/src/jvmAndroid/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.jvmAndroid.kt
index 986104fdb..a48ee39c6 100644
--- a/quartz/src/jvmAndroid/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.jvmAndroid.kt
+++ b/quartz/src/jvmAndroid/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.jvmAndroid.kt
@@ -65,6 +65,26 @@ actual class AESGCM actual constructor(
             null
         }
 
+    actual fun encrypt(
+        bytesToEncrypt: ByteArray,
+        aad: ByteArray,
+    ): ByteArray =
+        with(newCipher()) {
+            init(Cipher.ENCRYPT_MODE, keySpec(), param())
+            updateAAD(aad)
+            doFinal(bytesToEncrypt)
+        }
+
+    actual fun decrypt(
+        bytesToDecrypt: ByteArray,
+        aad: ByteArray,
+    ): ByteArray =
+        with(newCipher()) {
+            init(Cipher.DECRYPT_MODE, keySpec(), param())
+            updateAAD(aad)
+            doFinal(bytesToDecrypt)
+        }
+
     companion object {
         const val NAME = "aes-gcm"
     }
diff --git a/quartz/src/linuxMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.linux.kt b/quartz/src/linuxMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.linux.kt
index eb065059a..9536b80e5 100644
--- a/quartz/src/linuxMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.linux.kt
+++ b/quartz/src/linuxMain/kotlin/com/vitorpamplona/quartz/utils/ciphers/AESGCM.linux.kt
@@ -63,4 +63,22 @@ actual class AESGCM actual constructor(
             Log.w("AESGCM", "Failed to decrypt", e)
             null
         }
+
+    @OptIn(DelicateCryptographyApi::class)
+    actual fun encrypt(
+        bytesToEncrypt: ByteArray,
+        aad: ByteArray,
+    ): ByteArray =
+        with(cipher()) {
+            encryptWithIvBlocking(nonce, bytesToEncrypt, aad)
+        }
+
+    @OptIn(DelicateCryptographyApi::class)
+    actual fun decrypt(
+        bytesToDecrypt: ByteArray,
+        aad: ByteArray,
+    ): ByteArray =
+        with(cipher()) {
+            decryptWithIvBlocking(nonce, bytesToDecrypt, aad)
+        }
 }