diff --git a/keymaster/4.1/IKeymasterDevice.hal b/keymaster/4.1/IKeymasterDevice.hal
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+++ b/keymaster/4.1/IKeymasterDevice.hal
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+/*
+ * Copyright (C) 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.
+ */
+
+package android.hardware.keymaster@4.1;
+
+import @4.0::ErrorCode;
+import @4.0::HardwareAuthToken;
+import @4.0::IKeymasterDevice;
+import @4.0::KeyParameter;
+import @4.0::KeyPurpose;
+import @4.0::OperationHandle;
+import IOperation;
+
+/**
+ * @4.1::IKeymasterDevice is a minor extension to @4.0::IKeymasterDevice.  It adds support for
+ *
+ * - Partial hardware enforcment of UNLOCKED_DEVICE_REQUIRED keys;
+ * - Device-unique attestaion;
+ * - Early boot only keys;
+ * - Better cleanup of operations when clients die without completing or aborting them.
+ */
+interface IKeymasterDevice extends @4.0::IKeymasterDevice {
+    /**
+     * Called by client to notify the IKeymasterDevice that the device is now locked, and keys with
+     * the UNLOCKED_DEVICE_REQUIRED tag should no longer be usable.  When this function is called,
+     * the IKeymasterDevice should note the current timestamp, and attempts to use
+     * UNLOCKED_DEVICE_REQUIRED keys must be rejected with Error::DEVICE_LOCKED until an
+     * authentication token with a later timestamp is presented.  If the `passwordOnly' argument is
+     * set to true the sufficiently-recent authentication token must indicate that the user
+     * authenticated with a password, not a biometric.
+     *
+     * @param passwordOnly specifies whether the device must be unlocked with a password, rather
+     * than a biometric, before UNLOCKED_DEVICE_REQUIRED keys can be used.
+     */
+    deviceLocked(bool passwordOnly) generates (ErrorCode error);
+
+    /**
+     * Called by client to notify the IKeymasterDevice that the device has left the early boot
+     * state, and that keys with the EARLY_BOOT_ONLY tag may no longer be used.  All attempts to use
+     * an EARLY_BOOT_ONLY key after this method is called must fail with Error::INVALID_KEY_BLOB.
+     */
+    earlyBootEnded() generates (ErrorCode error);
+
+    /**
+     * Begins a cryptographic operation.  beginOp() is a variation on begin().  beginOp() has
+     * identical functionality to begin, but instead of an OperationHandle it returns an IOperation
+     * object.  An IKeymasterDevice HAL service must call linkToDeath() on the Operation before
+     * returning it, and the provided hidl_death_recipient, if called, must abort() the operation.
+     * This is to ensure that in the event a client crashes while an operation is in progress, the
+     * operation slot is freed and available for use by other clients.
+     *
+     * @4.1::IKeymasterDevices must implement both beginOp() and begin().
+     */
+    beginOp(KeyPurpose purpose, vec<uint8_t> keyBlob, vec<KeyParameter> inParams,
+        HardwareAuthToken authToken)
+        generates (ErrorCode error, vec<KeyParameter> outParam, IOperation operation);
+};