diff --git a/include/attestation/HmacKeyManager.h b/include/attestation/HmacKeyManager.h
new file mode 100644
index 0000000..571a361
--- /dev/null
+++ b/include/attestation/HmacKeyManager.h
@@ -0,0 +1,32 @@
+/*
+ * 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 <array>
+
+namespace android {
+/**
+ * Invalid value of HMAC - SHA256. Any events with this HMAC value will be marked as not verified.
+ */
+constexpr std::array<uint8_t, 32> INVALID_HMAC = {0};
+
+class HmacKeyManager {
+public:
+    HmacKeyManager();
+    std::array<uint8_t, 32> sign(const uint8_t* data, size_t size) const;
+private:
+    const std::array<uint8_t, 128> mHmacKey;
+};
+} // namespace android
\ No newline at end of file
diff --git a/include/input/Input.h b/include/input/Input.h
index d40ba43..7b66d3c 100644
--- a/include/input/Input.h
+++ b/include/input/Input.h
@@ -312,11 +312,6 @@
  */
 constexpr float AMOTION_EVENT_INVALID_CURSOR_POSITION = std::numeric_limits<float>::quiet_NaN();
 
-/**
- * Invalid value of HMAC - SHA256. Any events with this HMAC value will be marked as not verified.
- */
-constexpr std::array<uint8_t, 32> INVALID_HMAC = {0};
-
 /*
  * Pointer coordinate data.
  */
diff --git a/libs/attestation/Android.bp b/libs/attestation/Android.bp
new file mode 100644
index 0000000..b85aecd
--- /dev/null
+++ b/libs/attestation/Android.bp
@@ -0,0 +1,31 @@
+// 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.
+cc_library_static {
+    name: "libattestation",
+    cflags: [
+        "-Wall",
+        "-Wextra",
+        "-Werror",
+    ],
+    srcs: [
+        "HmacKeyManager.cpp"
+    ],
+
+    clang: true,
+
+    shared_libs: [
+        "liblog",
+        "libcrypto",
+    ],
+}
\ No newline at end of file
diff --git a/libs/attestation/HmacKeyManager.cpp b/libs/attestation/HmacKeyManager.cpp
new file mode 100644
index 0000000..b15f143
--- /dev/null
+++ b/libs/attestation/HmacKeyManager.cpp
@@ -0,0 +1,52 @@
+/*
+ * 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 <attestation/HmacKeyManager.h>
+#include <log/log.h>
+#include <openssl/hmac.h>
+#include <openssl/rand.h>
+
+namespace android {
+
+static std::array<uint8_t, 128> getRandomKey() {
+    std::array<uint8_t, 128> key;
+    if (RAND_bytes(key.data(), key.size()) != 1) {
+        LOG_ALWAYS_FATAL("Can't generate HMAC key");
+    }
+    return key;
+}
+
+HmacKeyManager::HmacKeyManager() : mHmacKey(getRandomKey()) {}
+
+std::array<uint8_t, 32> HmacKeyManager::sign(const uint8_t* data, size_t size) const {
+    // SHA256 always generates 32-bytes result
+    std::array<uint8_t, 32> hash;
+    unsigned int hashLen = 0;
+    uint8_t* result =
+            HMAC(EVP_sha256(), mHmacKey.data(), mHmacKey.size(), data, size, hash.data(), &hashLen);
+    if (result == nullptr) {
+        ALOGE("Could not sign the data using HMAC");
+        return INVALID_HMAC;
+    }
+
+    if (hashLen != hash.size()) {
+        ALOGE("HMAC-SHA256 has unexpected length");
+        return INVALID_HMAC;
+    }
+
+    return hash;
+}
+} // namespace android
\ No newline at end of file
diff --git a/libs/attestation/OWNERS b/libs/attestation/OWNERS
new file mode 100644
index 0000000..4dbb0ea
--- /dev/null
+++ b/libs/attestation/OWNERS
@@ -0,0 +1,2 @@
+chaviw@google.com
+svv@google.com
\ No newline at end of file
diff --git a/libs/attestation/TEST_MAPPING b/libs/attestation/TEST_MAPPING
new file mode 100644
index 0000000..43be638
--- /dev/null
+++ b/libs/attestation/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "libattestation_tests"
+    }
+  ]
+}
\ No newline at end of file
diff --git a/libs/attestation/tests/Android.bp b/libs/attestation/tests/Android.bp
new file mode 100644
index 0000000..6ce5ea1
--- /dev/null
+++ b/libs/attestation/tests/Android.bp
@@ -0,0 +1,28 @@
+// 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.
+
+cc_test {
+    name: "libattestation_tests",
+    test_suites: ["device-tests"],
+    srcs: [
+        "HmacKeyManager_test.cpp",
+    ],
+    static_libs: [
+        "libattestation",
+    ],
+    shared_libs: [
+        "liblog",
+        "libcrypto",
+    ],
+}
diff --git a/libs/attestation/tests/HmacKeyManager_test.cpp b/libs/attestation/tests/HmacKeyManager_test.cpp
new file mode 100644
index 0000000..7f7a408
--- /dev/null
+++ b/libs/attestation/tests/HmacKeyManager_test.cpp
@@ -0,0 +1,52 @@
+/*
+ * 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 <attestation/HmacKeyManager.h>
+#include <gtest/gtest.h>
+
+namespace android {
+
+class HmacKeyManagerTest : public testing::Test {
+protected:
+    HmacKeyManager mHmacKeyManager;
+};
+
+/**
+ * Ensure that separate calls to sign the same data are generating the same key.
+ * We avoid asserting against INVALID_HMAC. Since the key is random, there is a non-zero chance
+ * that a specific key and data combination would produce INVALID_HMAC, which would cause flaky
+ * tests.
+ */
+TEST_F(HmacKeyManagerTest, GeneratedHmac_IsConsistent) {
+    std::array<uint8_t, 10> data = {4, 3, 5, 1, 8, 5, 2, 7, 1, 8};
+
+    std::array<uint8_t, 32> hmac1 = mHmacKeyManager.sign(data.data(), sizeof(data));
+    std::array<uint8_t, 32> hmac2 = mHmacKeyManager.sign(data.data(), sizeof(data));
+    ASSERT_EQ(hmac1, hmac2);
+}
+
+/**
+ * Ensure that changes in the hmac verification data produce a different hmac.
+ */
+TEST_F(HmacKeyManagerTest, GeneratedHmac_ChangesWhenFieldsChange) {
+    std::array<uint8_t, 10> data = {4, 3, 5, 1, 8, 5, 2, 7, 1, 8};
+    std::array<uint8_t, 32> initialHmac = mHmacKeyManager.sign(data.data(), sizeof(data));
+
+    data[2] = 2;
+    ASSERT_NE(initialHmac, mHmacKeyManager.sign(data.data(), sizeof(data)));
+}
+
+} // namespace android
\ No newline at end of file
diff --git a/libs/input/Input.cpp b/libs/input/Input.cpp
index 51910fe..692c65d 100644
--- a/libs/input/Input.cpp
+++ b/libs/input/Input.cpp
@@ -17,6 +17,7 @@
 #define LOG_TAG "Input"
 //#define LOG_NDEBUG 0
 
+#include <attestation/HmacKeyManager.h>
 #include <cutils/compiler.h>
 #include <limits.h>
 #include <string.h>
diff --git a/libs/input/KeyCharacterMap.cpp b/libs/input/KeyCharacterMap.cpp
index fd35131..7ac8a2e 100644
--- a/libs/input/KeyCharacterMap.cpp
+++ b/libs/input/KeyCharacterMap.cpp
@@ -24,9 +24,10 @@
 #endif
 
 #include <android/keycodes.h>
+#include <attestation/HmacKeyManager.h>
 #include <input/InputEventLabels.h>
-#include <input/Keyboard.h>
 #include <input/KeyCharacterMap.h>
+#include <input/Keyboard.h>
 
 #include <utils/Log.h>
 #include <utils/Errors.h>
diff --git a/libs/input/tests/InputEvent_test.cpp b/libs/input/tests/InputEvent_test.cpp
index 069bc0e..601d8da 100644
--- a/libs/input/tests/InputEvent_test.cpp
+++ b/libs/input/tests/InputEvent_test.cpp
@@ -17,6 +17,7 @@
 #include <array>
 #include <math.h>
 
+#include <attestation/HmacKeyManager.h>
 #include <binder/Parcel.h>
 #include <gtest/gtest.h>
 #include <input/Input.h>
diff --git a/libs/input/tests/InputPublisherAndConsumer_test.cpp b/libs/input/tests/InputPublisherAndConsumer_test.cpp
index e1f2562..1452745 100644
--- a/libs/input/tests/InputPublisherAndConsumer_test.cpp
+++ b/libs/input/tests/InputPublisherAndConsumer_test.cpp
@@ -20,11 +20,12 @@
 #include <sys/mman.h>
 #include <time.h>
 
+#include <attestation/HmacKeyManager.h>
 #include <cutils/ashmem.h>
 #include <gtest/gtest.h>
 #include <input/InputTransport.h>
-#include <utils/Timers.h>
 #include <utils/StopWatch.h>
+#include <utils/Timers.h>
 
 namespace android {
 
diff --git a/libs/input/tests/VelocityTracker_test.cpp b/libs/input/tests/VelocityTracker_test.cpp
index e7db4b0..d049d05 100644
--- a/libs/input/tests/VelocityTracker_test.cpp
+++ b/libs/input/tests/VelocityTracker_test.cpp
@@ -21,6 +21,7 @@
 #include <math.h>
 
 #include <android-base/stringprintf.h>
+#include <attestation/HmacKeyManager.h>
 #include <gtest/gtest.h>
 #include <input/VelocityTracker.h>
 
diff --git a/libs/input/tests/VerifiedInputEvent_test.cpp b/libs/input/tests/VerifiedInputEvent_test.cpp
index 21cfe8c..36f87b8 100644
--- a/libs/input/tests/VerifiedInputEvent_test.cpp
+++ b/libs/input/tests/VerifiedInputEvent_test.cpp
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include <attestation/HmacKeyManager.h>
 #include <gtest/gtest.h>
 #include <input/Input.h>
 
diff --git a/services/inputflinger/Android.bp b/services/inputflinger/Android.bp
index a0de607..96e6207 100644
--- a/services/inputflinger/Android.bp
+++ b/services/inputflinger/Android.bp
@@ -59,6 +59,9 @@
         "libutils",
         "libui",
     ],
+    static_libs: [
+        "libattestation",
+    ],
 }
 
 cc_library_shared {
diff --git a/services/inputflinger/benchmarks/Android.bp b/services/inputflinger/benchmarks/Android.bp
index 066a816..9abf8b1 100644
--- a/services/inputflinger/benchmarks/Android.bp
+++ b/services/inputflinger/benchmarks/Android.bp
@@ -18,6 +18,7 @@
         "libutils",
     ],
     static_libs: [
+        "libattestation",
         "libinputdispatcher",
     ],
 }
diff --git a/services/inputflinger/dispatcher/Android.bp b/services/inputflinger/dispatcher/Android.bp
index d29d8df..ff9aac9 100644
--- a/services/inputflinger/dispatcher/Android.bp
+++ b/services/inputflinger/dispatcher/Android.bp
@@ -48,6 +48,9 @@
         "libui",
         "libutils",
     ],
+    static_libs: [
+        "libattestation",
+    ],
     header_libs: [
         "libinputdispatcher_headers",
     ],
diff --git a/services/inputflinger/dispatcher/InputDispatcher.cpp b/services/inputflinger/dispatcher/InputDispatcher.cpp
index 9c8481c..b428c4e 100644
--- a/services/inputflinger/dispatcher/InputDispatcher.cpp
+++ b/services/inputflinger/dispatcher/InputDispatcher.cpp
@@ -53,8 +53,6 @@
 #include <input/InputWindow.h>
 #include <log/log.h>
 #include <log/log_event_list.h>
-#include <openssl/hmac.h>
-#include <openssl/rand.h>
 #include <powermanager/PowerManager.h>
 #include <statslog.h>
 #include <unistd.h>
@@ -344,53 +342,6 @@
     }
 }
 
-static std::array<uint8_t, 128> getRandomKey() {
-    std::array<uint8_t, 128> key;
-    if (RAND_bytes(key.data(), key.size()) != 1) {
-        LOG_ALWAYS_FATAL("Can't generate HMAC key");
-    }
-    return key;
-}
-
-// --- HmacKeyManager ---
-
-HmacKeyManager::HmacKeyManager() : mHmacKey(getRandomKey()) {}
-
-std::array<uint8_t, 32> HmacKeyManager::sign(const VerifiedInputEvent& event) const {
-    size_t size;
-    switch (event.type) {
-        case VerifiedInputEvent::Type::KEY: {
-            size = sizeof(VerifiedKeyEvent);
-            break;
-        }
-        case VerifiedInputEvent::Type::MOTION: {
-            size = sizeof(VerifiedMotionEvent);
-            break;
-        }
-    }
-    const uint8_t* start = reinterpret_cast<const uint8_t*>(&event);
-    return sign(start, size);
-}
-
-std::array<uint8_t, 32> HmacKeyManager::sign(const uint8_t* data, size_t size) const {
-    // SHA256 always generates 32-bytes result
-    std::array<uint8_t, 32> hash;
-    unsigned int hashLen = 0;
-    uint8_t* result =
-            HMAC(EVP_sha256(), mHmacKey.data(), mHmacKey.size(), data, size, hash.data(), &hashLen);
-    if (result == nullptr) {
-        ALOGE("Could not sign the data using HMAC");
-        return INVALID_HMAC;
-    }
-
-    if (hashLen != hash.size()) {
-        ALOGE("HMAC-SHA256 has unexpected length");
-        return INVALID_HMAC;
-    }
-
-    return hash;
-}
-
 // --- InputDispatcher ---
 
 InputDispatcher::InputDispatcher(const sp<InputDispatcherPolicyInterface>& policy)
@@ -2682,6 +2633,22 @@
     }
 }
 
+std::array<uint8_t, 32> InputDispatcher::sign(const VerifiedInputEvent& event) const {
+    size_t size;
+    switch (event.type) {
+        case VerifiedInputEvent::Type::KEY: {
+            size = sizeof(VerifiedKeyEvent);
+            break;
+        }
+        case VerifiedInputEvent::Type::MOTION: {
+            size = sizeof(VerifiedMotionEvent);
+            break;
+        }
+    }
+    const uint8_t* start = reinterpret_cast<const uint8_t*>(&event);
+    return mHmacKeyManager.sign(start, size);
+}
+
 const std::array<uint8_t, 32> InputDispatcher::getSignature(
         const MotionEntry& motionEntry, const DispatchEntry& dispatchEntry) const {
     int32_t actionMasked = dispatchEntry.resolvedAction & AMOTION_EVENT_ACTION_MASK;
@@ -2691,7 +2658,7 @@
         VerifiedMotionEvent verifiedEvent = verifiedMotionEventFromMotionEntry(motionEntry);
         verifiedEvent.actionMasked = actionMasked;
         verifiedEvent.flags = dispatchEntry.resolvedFlags & VERIFIED_MOTION_EVENT_FLAGS;
-        return mHmacKeyManager.sign(verifiedEvent);
+        return sign(verifiedEvent);
     }
     return INVALID_HMAC;
 }
@@ -2701,7 +2668,7 @@
     VerifiedKeyEvent verifiedEvent = verifiedKeyEventFromKeyEntry(keyEntry);
     verifiedEvent.flags = dispatchEntry.resolvedFlags & VERIFIED_KEY_EVENT_FLAGS;
     verifiedEvent.action = dispatchEntry.resolvedAction;
-    return mHmacKeyManager.sign(verifiedEvent);
+    return sign(verifiedEvent);
 }
 
 void InputDispatcher::finishDispatchCycleLocked(nsecs_t currentTime,
@@ -3549,7 +3516,7 @@
             const KeyEvent& keyEvent = static_cast<const KeyEvent&>(event);
             VerifiedKeyEvent verifiedKeyEvent = verifiedKeyEventFromKeyEvent(keyEvent);
             result = std::make_unique<VerifiedKeyEvent>(verifiedKeyEvent);
-            calculatedHmac = mHmacKeyManager.sign(verifiedKeyEvent);
+            calculatedHmac = sign(verifiedKeyEvent);
             break;
         }
         case AINPUT_EVENT_TYPE_MOTION: {
@@ -3557,7 +3524,7 @@
             VerifiedMotionEvent verifiedMotionEvent =
                     verifiedMotionEventFromMotionEvent(motionEvent);
             result = std::make_unique<VerifiedMotionEvent>(verifiedMotionEvent);
-            calculatedHmac = mHmacKeyManager.sign(verifiedMotionEvent);
+            calculatedHmac = sign(verifiedMotionEvent);
             break;
         }
         default: {
diff --git a/services/inputflinger/dispatcher/InputDispatcher.h b/services/inputflinger/dispatcher/InputDispatcher.h
index c52d256..93d3fde 100644
--- a/services/inputflinger/dispatcher/InputDispatcher.h
+++ b/services/inputflinger/dispatcher/InputDispatcher.h
@@ -31,6 +31,7 @@
 #include "TouchState.h"
 #include "TouchedWindow.h"
 
+#include <attestation/HmacKeyManager.h>
 #include <input/Input.h>
 #include <input/InputApplication.h>
 #include <input/InputTransport.h>
@@ -58,16 +59,6 @@
 
 class Connection;
 
-class HmacKeyManager {
-public:
-    HmacKeyManager();
-    std::array<uint8_t, 32> sign(const VerifiedInputEvent& event) const;
-
-private:
-    std::array<uint8_t, 32> sign(const uint8_t* data, size_t size) const;
-    const std::array<uint8_t, 128> mHmacKey;
-};
-
 /* Dispatches events to input targets.  Some functions of the input dispatcher, such as
  * identifying input targets, are controlled by a separate policy object.
  *
@@ -133,6 +124,8 @@
     virtual status_t unregisterInputChannel(const InputChannel& inputChannel) override;
     virtual status_t pilferPointers(const sp<IBinder>& token) override;
 
+    std::array<uint8_t, 32> sign(const VerifiedInputEvent& event) const;
+
 private:
     enum class DropReason {
         NOT_DROPPED,
diff --git a/services/inputflinger/tests/InputDispatcher_test.cpp b/services/inputflinger/tests/InputDispatcher_test.cpp
index da50af5..3e0b5e8 100644
--- a/services/inputflinger/tests/InputDispatcher_test.cpp
+++ b/services/inputflinger/tests/InputDispatcher_test.cpp
@@ -294,70 +294,6 @@
     }
 };
 
-// --- HmacKeyManagerTest ---
-
-class HmacKeyManagerTest : public testing::Test {
-protected:
-    HmacKeyManager mHmacKeyManager;
-};
-
-/**
- * Ensure that separate calls to sign the same data are generating the same key.
- * We avoid asserting against INVALID_HMAC. Since the key is random, there is a non-zero chance
- * that a specific key and data combination would produce INVALID_HMAC, which would cause flaky
- * tests.
- */
-TEST_F(HmacKeyManagerTest, GeneratedHmac_IsConsistent) {
-    KeyEvent event = getTestKeyEvent();
-    VerifiedKeyEvent verifiedEvent = verifiedKeyEventFromKeyEvent(event);
-
-    std::array<uint8_t, 32> hmac1 = mHmacKeyManager.sign(verifiedEvent);
-    std::array<uint8_t, 32> hmac2 = mHmacKeyManager.sign(verifiedEvent);
-    ASSERT_EQ(hmac1, hmac2);
-}
-
-/**
- * Ensure that changes in VerifiedKeyEvent produce a different hmac.
- */
-TEST_F(HmacKeyManagerTest, GeneratedHmac_ChangesWhenFieldsChange) {
-    KeyEvent event = getTestKeyEvent();
-    VerifiedKeyEvent verifiedEvent = verifiedKeyEventFromKeyEvent(event);
-    std::array<uint8_t, 32> initialHmac = mHmacKeyManager.sign(verifiedEvent);
-
-    verifiedEvent.deviceId += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-
-    verifiedEvent.source += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-
-    verifiedEvent.eventTimeNanos += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-
-    verifiedEvent.displayId += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-
-    verifiedEvent.action += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-
-    verifiedEvent.downTimeNanos += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-
-    verifiedEvent.flags += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-
-    verifiedEvent.keyCode += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-
-    verifiedEvent.scanCode += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-
-    verifiedEvent.metaState += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-
-    verifiedEvent.repeatCount += 1;
-    ASSERT_NE(initialHmac, mHmacKeyManager.sign(verifiedEvent));
-}
-
 // --- InputDispatcherTest ---
 
 class InputDispatcherTest : public testing::Test {
@@ -2027,6 +1963,63 @@
     EXPECT_EQ(motionArgs.buttonState, verifiedMotion.buttonState);
 }
 
+/**
+ * Ensure that separate calls to sign the same data are generating the same key.
+ * We avoid asserting against INVALID_HMAC. Since the key is random, there is a non-zero chance
+ * that a specific key and data combination would produce INVALID_HMAC, which would cause flaky
+ * tests.
+ */
+TEST_F(InputDispatcherTest, GeneratedHmac_IsConsistent) {
+    KeyEvent event = getTestKeyEvent();
+    VerifiedKeyEvent verifiedEvent = verifiedKeyEventFromKeyEvent(event);
+
+    std::array<uint8_t, 32> hmac1 = mDispatcher->sign(verifiedEvent);
+    std::array<uint8_t, 32> hmac2 = mDispatcher->sign(verifiedEvent);
+    ASSERT_EQ(hmac1, hmac2);
+}
+
+/**
+ * Ensure that changes in VerifiedKeyEvent produce a different hmac.
+ */
+TEST_F(InputDispatcherTest, GeneratedHmac_ChangesWhenFieldsChange) {
+    KeyEvent event = getTestKeyEvent();
+    VerifiedKeyEvent verifiedEvent = verifiedKeyEventFromKeyEvent(event);
+    std::array<uint8_t, 32> initialHmac = mDispatcher->sign(verifiedEvent);
+
+    verifiedEvent.deviceId += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+
+    verifiedEvent.source += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+
+    verifiedEvent.eventTimeNanos += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+
+    verifiedEvent.displayId += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+
+    verifiedEvent.action += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+
+    verifiedEvent.downTimeNanos += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+
+    verifiedEvent.flags += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+
+    verifiedEvent.keyCode += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+
+    verifiedEvent.scanCode += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+
+    verifiedEvent.metaState += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+
+    verifiedEvent.repeatCount += 1;
+    ASSERT_NE(initialHmac, mDispatcher->sign(verifiedEvent));
+}
+
 class InputDispatcherKeyRepeatTest : public InputDispatcherTest {
 protected:
     static constexpr nsecs_t KEY_REPEAT_TIMEOUT = 40 * 1000000; // 40 ms