diff --git a/keystore2/aaid/aaid.cpp b/keystore2/aaid/aaid.cpp
new file mode 100644
index 0000000..fd3faf6
--- /dev/null
+++ b/keystore2/aaid/aaid.cpp
@@ -0,0 +1,42 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include "aaid.hpp"
+
+#include <keystore/keystore_attestation_id.h>
+
+using android::security::gather_attestation_application_id;
+
+uint32_t aaid_keystore_attestation_id(uint32_t uid, uint8_t* aaid, size_t* aaid_size) {
+    static_assert(sizeof(uint32_t) == sizeof(uid_t), "uid_t has unexpected size");
+    static_assert(sizeof(uint32_t) == sizeof(android::status_t), "status_t has unexpected size");
+    static_assert(KEY_ATTESTATION_APPLICATION_ID_MAX_SIZE ==
+                      android::security::KEY_ATTESTATION_APPLICATION_ID_MAX_SIZE,
+                  "KEY_ATTESTATION_APPLICATION_ID_MAX_SIZE sizes don't match.");
+    auto result = gather_attestation_application_id(uid);
+    if (!result.isOk()) {
+        return result.status();
+    }
+    if (result.value().size() > KEY_ATTESTATION_APPLICATION_ID_MAX_SIZE) {
+        return ::android::NO_MEMORY;
+    }
+    if (*aaid_size != KEY_ATTESTATION_APPLICATION_ID_MAX_SIZE) {
+        return ::android::BAD_VALUE;
+    }
+    std::copy(result.value().begin(), result.value().end(), aaid);
+    *aaid_size = result.value().size();
+    return ::android::OK;
+}