diff --git a/nearby/service/java/com/android/server/nearby/common/bluetooth/BluetoothException.java b/nearby/service/java/com/android/server/nearby/common/bluetooth/BluetoothException.java
index 83d4a23..db2e1cc 100644
--- a/nearby/service/java/com/android/server/nearby/common/bluetooth/BluetoothException.java
+++ b/nearby/service/java/com/android/server/nearby/common/bluetooth/BluetoothException.java
@@ -20,10 +20,12 @@
  * {@link Exception} thrown during a Bluetooth operation.
  */
 public class BluetoothException extends Exception {
+    /** Constructor. */
     public BluetoothException(String message) {
         super(message);
     }
 
+    /** Constructor. */
     public BluetoothException(String message, Throwable throwable) {
         super(message, throwable);
     }
diff --git a/nearby/service/java/com/android/server/nearby/common/bluetooth/BluetoothGattException.java b/nearby/service/java/com/android/server/nearby/common/bluetooth/BluetoothGattException.java
new file mode 100644
index 0000000..5ac4882
--- /dev/null
+++ b/nearby/service/java/com/android/server/nearby/common/bluetooth/BluetoothGattException.java
@@ -0,0 +1,41 @@
+/*
+ * Copyright 2021 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 com.android.server.nearby.common.bluetooth;
+
+/**
+ * Exception for Bluetooth GATT operations.
+ */
+public class BluetoothGattException extends BluetoothException {
+    private final int mErrorCode;
+
+    /** Constructor. */
+    public BluetoothGattException(String message, int errorCode) {
+        super(message);
+        mErrorCode = errorCode;
+    }
+
+    /** Constructor. */
+    public BluetoothGattException(String message, int errorCode, Throwable cause) {
+        super(message, cause);
+        mErrorCode = errorCode;
+    }
+
+    /** Returns Gatt error code. */
+    public int getGattErrorCode() {
+        return mErrorCode;
+    }
+}
diff --git a/nearby/service/java/com/android/server/nearby/common/bluetooth/BluetoothTimeoutException.java b/nearby/service/java/com/android/server/nearby/common/bluetooth/BluetoothTimeoutException.java
new file mode 100644
index 0000000..30fd188
--- /dev/null
+++ b/nearby/service/java/com/android/server/nearby/common/bluetooth/BluetoothTimeoutException.java
@@ -0,0 +1,33 @@
+/*
+ * Copyright 2021 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 com.android.server.nearby.common.bluetooth;
+
+/**
+ * {@link Exception} thrown during a Bluetooth operation when a timeout occurs.
+ */
+public class BluetoothTimeoutException extends BluetoothException {
+
+    /** Constructor. */
+    public BluetoothTimeoutException(String message) {
+        super(message);
+    }
+
+    /** Constructor. */
+    public BluetoothTimeoutException(String message, Throwable throwable) {
+        super(message, throwable);
+    }
+}
diff --git a/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/AesEcbSingleBlockEncryption.java b/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/AesEcbSingleBlockEncryption.java
new file mode 100644
index 0000000..547931e
--- /dev/null
+++ b/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/AesEcbSingleBlockEncryption.java
@@ -0,0 +1,78 @@
+/*
+ * Copyright 2021 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 com.android.server.nearby.common.bluetooth.fastpair;
+
+import android.annotation.SuppressLint;
+
+import java.security.GeneralSecurityException;
+import java.security.NoSuchAlgorithmException;
+
+import javax.crypto.Cipher;
+import javax.crypto.KeyGenerator;
+import javax.crypto.spec.SecretKeySpec;
+
+/**
+ * Utilities used for encrypting and decrypting Fast Pair packets.
+ */
+// SuppressLint for ""ecb encryption mode should not be used".
+// Reasons:
+//    1. FastPair data is guaranteed to be only 1 AES block in size, ECB is secure.
+//    2. In each case, the encrypted data is less than 16-bytes and is
+//       padded up to 16-bytes using random data to fill the rest of the byte array,
+//       so the plaintext will never be the same.
+@SuppressLint("GetInstance")
+public final class AesEcbSingleBlockEncryption {
+
+    public static final int AES_BLOCK_LENGTH = 16;
+    public static final int KEY_LENGTH = 16;
+
+    private AesEcbSingleBlockEncryption() {
+    }
+
+    /**
+     * Generates a 16-byte AES key.
+     */
+    public static byte[] generateKey() throws NoSuchAlgorithmException {
+        KeyGenerator generator = KeyGenerator.getInstance("AES");
+        generator.init(KEY_LENGTH * 8); // Ensure a 16-byte key is always used.
+        return generator.generateKey().getEncoded();
+    }
+
+    /**
+     * Encrypts data with the provided secret.
+     */
+    public static byte[] encrypt(byte[] secret, byte[] data) throws GeneralSecurityException {
+        return doEncryption(Cipher.ENCRYPT_MODE, secret, data);
+    }
+
+    /**
+     * Decrypts data with the provided secret.
+     */
+    public static byte[] decrypt(byte[] secret, byte[] data) throws GeneralSecurityException {
+        return doEncryption(Cipher.DECRYPT_MODE, secret, data);
+    }
+
+    private static byte[] doEncryption(int mode, byte[] secret, byte[] data)
+            throws GeneralSecurityException {
+        if (data.length != AES_BLOCK_LENGTH) {
+            throw new IllegalArgumentException("This encrypter only supports 16-byte inputs.");
+        }
+        Cipher cipher = Cipher.getInstance("AES/ECB/NoPadding");
+        cipher.init(mode, new SecretKeySpec(secret, "AES"));
+        return cipher.doFinal(data);
+    }
+}
diff --git a/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/FastPairConstants.java b/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/FastPairConstants.java
new file mode 100644
index 0000000..0ff1bf2
--- /dev/null
+++ b/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/FastPairConstants.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2021 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 com.android.server.nearby.common.bluetooth.fastpair;
+
+import android.bluetooth.BluetoothDevice;
+
+/** Constants to share with other team. */
+public class FastPairConstants {
+    private static final String PACKAGE_NAME = "com.android.server.nearby";
+    private static final String PREFIX = PACKAGE_NAME + ".common.bluetooth.fastpair.";
+
+    /** MODEL_ID item name for extended intent field. */
+    public static final String EXTRA_MODEL_ID = PREFIX + "MODEL_ID";
+    /** CONNECTION_ID item name for extended intent field. */
+    public static final String EXTRA_CONNECTION_ID = PREFIX + "CONNECTION_ID";
+    /** BLUETOOTH_MAC_ADDRESS item name for extended intent field. */
+    public static final String EXTRA_BLUETOOTH_MAC_ADDRESS = PREFIX + "BLUETOOTH_MAC_ADDRESS";
+    /** COMPANION_SCAN_ITEM item name for extended intent field. */
+    public static final String EXTRA_SCAN_ITEM = PREFIX + "COMPANION_SCAN_ITEM";
+    /** BOND_RESULT item name for extended intent field. */
+    public static final String EXTRA_BOND_RESULT = PREFIX + "EXTRA_BOND_RESULT";
+
+    /**
+     * The bond result of the {@link BluetoothDevice} when FastPair launches the companion app, it
+     * means device is BONDED but the pairing process is not triggered by FastPair.
+     */
+    public static final int BOND_RESULT_SUCCESS_WITHOUT_FP = 0;
+
+    /**
+     * The bond result of the {@link BluetoothDevice} when FastPair launches the companion app, it
+     * means device is BONDED and the pairing process is triggered by FastPair.
+     */
+    public static final int BOND_RESULT_SUCCESS_WITH_FP = 1;
+
+    /**
+     * The bond result of the {@link BluetoothDevice} when FastPair launches the companion app, it
+     * means the pairing process triggered by FastPair is failed due to the lack of PIN code.
+     */
+    public static final int BOND_RESULT_FAIL_WITH_FP_WITHOUT_PIN = 2;
+
+    /**
+     * The bond result of the {@link BluetoothDevice} when FastPair launches the companion app, it
+     * means the pairing process triggered by FastPair is failed due to the PIN code is not
+     * confirmed by the user.
+     */
+    public static final int BOND_RESULT_FAIL_WITH_FP_WITH_PIN_NOT_CONFIRMED = 3;
+
+    /**
+     * The bond result of the {@link BluetoothDevice} when FastPair launches the companion app, it
+     * means the pairing process triggered by FastPair is failed due to the user thinks the PIN is
+     * wrong.
+     */
+    public static final int BOND_RESULT_FAIL_WITH_FP_WITH_PIN_WRONG = 4;
+
+    /**
+     * The bond result of the {@link BluetoothDevice} when FastPair launches the companion app, it
+     * means the pairing process triggered by FastPair is failed even after the user confirmed the
+     * PIN code is correct.
+     */
+    public static final int BOND_RESULT_FAIL_WITH_FP_WITH_PIN_CORRECT = 5;
+
+    private FastPairConstants() {}
+}
diff --git a/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/SignalLostException.java b/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/SignalLostException.java
new file mode 100644
index 0000000..244ee66
--- /dev/null
+++ b/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/SignalLostException.java
@@ -0,0 +1,25 @@
+/*
+ * Copyright 2021 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 com.android.server.nearby.common.bluetooth.fastpair;
+
+/** Base class for fast pair signal lost exceptions. */
+public class SignalLostException extends PairingException {
+    SignalLostException(String message, Exception e) {
+        super(message);
+        initCause(e);
+    }
+}
diff --git a/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/SignalRotatedException.java b/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/SignalRotatedException.java
new file mode 100644
index 0000000..d0d2a5d
--- /dev/null
+++ b/nearby/service/java/com/android/server/nearby/common/bluetooth/fastpair/SignalRotatedException.java
@@ -0,0 +1,33 @@
+/*
+ * Copyright 2021 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 com.android.server.nearby.common.bluetooth.fastpair;
+
+/** Base class for fast pair signal rotated exceptions. */
+public class SignalRotatedException extends PairingException {
+    private final String mNewAddress;
+
+    SignalRotatedException(String message, String newAddress, Exception e) {
+        super(message);
+        this.mNewAddress = newAddress;
+        initCause(e);
+    }
+
+    /** Returns the new BLE address for the model ID. */
+    public String getNewAddress() {
+        return mNewAddress;
+    }
+}
diff --git a/nearby/service/java/com/android/server/nearby/common/bluetooth/testability/NonnullProvider.java b/nearby/service/java/com/android/server/nearby/common/bluetooth/testability/NonnullProvider.java
new file mode 100644
index 0000000..16abd99
--- /dev/null
+++ b/nearby/service/java/com/android/server/nearby/common/bluetooth/testability/NonnullProvider.java
@@ -0,0 +1,27 @@
+/*
+ * Copyright 2021 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 com.android.server.nearby.common.bluetooth.testability;
+
+/**
+ * Provider that returns non-null instances.
+ *
+ * @param <T> Type of provided instance.
+ */
+public interface NonnullProvider<T> {
+    /** Get a non-null instance. */
+    T get();
+}
diff --git a/nearby/tests/src/com/android/server/nearby/common/bluetooth/fastpair/AesEcbSingleBlockEncryptionTest.java b/nearby/tests/src/com/android/server/nearby/common/bluetooth/fastpair/AesEcbSingleBlockEncryptionTest.java
new file mode 100644
index 0000000..0e13133
--- /dev/null
+++ b/nearby/tests/src/com/android/server/nearby/common/bluetooth/fastpair/AesEcbSingleBlockEncryptionTest.java
@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2021 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 com.android.server.nearby.common.bluetooth.fastpair;
+
+import static com.google.common.io.BaseEncoding.base16;
+import static com.google.common.truth.Truth.assertThat;
+
+import android.platform.test.annotations.Presubmit;
+
+import androidx.test.filters.SmallTest;
+import androidx.test.runner.AndroidJUnit4;
+
+import com.google.common.primitives.Bytes;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+/** Unit tests for {@link AesEcbSingleBlockEncryption}. */
+@Presubmit
+@SmallTest
+@RunWith(AndroidJUnit4.class)
+public class AesEcbSingleBlockEncryptionTest {
+
+    private static final byte[] PLAINTEXT = base16().decode("F30F4E786C59A7BBF3873B5A49BA97EA");
+
+    @Test
+    public void encryptDecryptSuccessful() throws Exception {
+        byte[] secret = AesEcbSingleBlockEncryption.generateKey();
+        byte[] encrypted = AesEcbSingleBlockEncryption.encrypt(secret, PLAINTEXT);
+        assertThat(encrypted).isNotEqualTo(PLAINTEXT);
+        byte[] decrypted = AesEcbSingleBlockEncryption.decrypt(secret, encrypted);
+        assertThat(decrypted).isEqualTo(PLAINTEXT);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void encryptionSizeLimitationEnforced() throws Exception {
+        byte[] secret = AesEcbSingleBlockEncryption.generateKey();
+        byte[] largePacket = Bytes.concat(PLAINTEXT, PLAINTEXT);
+        AesEcbSingleBlockEncryption.encrypt(secret, largePacket);
+    }
+
+    @Test(expected = IllegalArgumentException.class)
+    public void decryptionSizeLimitationEnforced() throws Exception {
+        byte[] secret = AesEcbSingleBlockEncryption.generateKey();
+        byte[] largePacket = Bytes.concat(PLAINTEXT, PLAINTEXT);
+        AesEcbSingleBlockEncryption.decrypt(secret, largePacket);
+    }
+}