diff --git a/identity/aidl/default/WritableIdentityCredential.h b/identity/aidl/default/WritableIdentityCredential.h
new file mode 100644
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+++ b/identity/aidl/default/WritableIdentityCredential.h
@@ -0,0 +1,90 @@
+/*
+ * Copyright 2019, 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.
+ */
+
+#ifndef ANDROID_HARDWARE_IDENTITY_WRITABLEIDENTITYCREDENTIAL_H
+#define ANDROID_HARDWARE_IDENTITY_WRITABLEIDENTITYCREDENTIAL_H
+
+#include <aidl/android/hardware/identity/BnWritableIdentityCredential.h>
+#include <android/hardware/identity/support/IdentityCredentialSupport.h>
+
+#include <cppbor.h>
+
+namespace aidl::android::hardware::identity {
+
+using ::std::string;
+using ::std::vector;
+
+class WritableIdentityCredential : public BnWritableIdentityCredential {
+  public:
+    WritableIdentityCredential(const string& docType, bool testCredential)
+        : docType_(docType), testCredential_(testCredential) {}
+
+    // Creates the Credential Key. Returns false on failure. Must be called
+    // right after construction.
+    bool initialize();
+
+    // Methods from IWritableIdentityCredential follow.
+    ndk::ScopedAStatus getAttestationCertificate(const vector<int8_t>& attestationApplicationId,
+                                                 const vector<int8_t>& attestationChallenge,
+                                                 vector<Certificate>* outCertificateChain) override;
+
+    ndk::ScopedAStatus startPersonalization(int32_t accessControlProfileCount,
+                                            const vector<int32_t>& entryCounts) override;
+
+    ndk::ScopedAStatus addAccessControlProfile(
+            int32_t id, const Certificate& readerCertificate, bool userAuthenticationRequired,
+            int64_t timeoutMillis, int64_t secureUserId,
+            SecureAccessControlProfile* outSecureAccessControlProfile) override;
+
+    ndk::ScopedAStatus beginAddEntry(const vector<int32_t>& accessControlProfileIds,
+                                     const string& nameSpace, const string& name,
+                                     int32_t entrySize) override;
+
+    ndk::ScopedAStatus addEntryValue(const vector<int8_t>& content,
+                                     vector<int8_t>* outEncryptedContent) override;
+
+    ndk::ScopedAStatus finishAddingEntries(
+            vector<int8_t>* outCredentialData,
+            vector<int8_t>* outProofOfProvisioningSignature) override;
+
+    // private:
+    string docType_;
+    bool testCredential_;
+
+    // These are set in initialize().
+    vector<uint8_t> storageKey_;
+    vector<uint8_t> credentialPrivKey_;
+    vector<uint8_t> credentialPubKey_;
+
+    // These fields are initialized during startPersonalization()
+    size_t numAccessControlProfileRemaining_;
+    vector<int32_t> remainingEntryCounts_;
+    cppbor::Array signedDataAccessControlProfiles_;
+    cppbor::Map signedDataNamespaces_;
+    cppbor::Array signedDataCurrentNamespace_;
+
+    // These fields are initialized during beginAddEntry()
+    size_t entryRemainingBytes_;
+    vector<uint8_t> entryAdditionalData_;
+    string entryNameSpace_;
+    string entryName_;
+    vector<int32_t> entryAccessControlProfileIds_;
+    vector<uint8_t> entryBytes_;
+};
+
+}  // namespace aidl::android::hardware::identity
+
+#endif  // ANDROID_HARDWARE_IDENTITY_WRITABLEIDENTITYCREDENTIAL_H