Secure a database with customer-managed encryption keys (CMEK)

This page describes how to use manually-created customer-managed encryption keys (CMEK) for Spanner.

To learn more about CMEK, see the Customer-managed encryption keys (CMEK) overview.

Create a CMEK-enabled database

Create a key in Cloud Key Management Service (Cloud KMS). Spanner supports creating to following Cloud KMS types:
The key must be in the same location as your Spanner instance. For example, if your Spanner instance configuration is in us-west1, then your Cloud KMS key ring location must also be us-west1.

Not every Spanner multi-region instance configuration has a corresponding Cloud KMS key ring location. For Spanner databases in custom, dual-region, or multi-region instance configurations, you can use multiple regional (single-region) Cloud KMS keys to protect your database. For example:
- If your Spanner database is in the multi-region instance configuration nam14, then you can create Cloud KMS keys in us-east4, northamerica-northeast1, and us-east1.
- If your database is in a custom instance configuration that uses nam3 as the base instance configuration with an additional read-only replica in us-central2, then you can create Cloud KMS keys in us-east4, us-east1, us-central1, and us-central2.
Note: Protecting a CMEK database with a mix of Cloud KMS multi-region and single-region keys is not supported.

Optional: To see a list of the replica locations in your Spanner instance configuration, use the gcloud spanner instances get-locations command:
```
gcloud spanner instances get-locations <var>INSTANCE_ID</var>
```
For more information, see the following resources:
- Cloud KMS locations
- Spanner locations
Grant Spanner access to the key.
1. In Cloud Shell, create and display the service agent, or display it if the account already exists:
```
gcloud beta services identity create --service=spanner.googleapis.com \
    --project=PROJECT_ID
```
  If you're prompted to install the gcloud Beta Commands component, type Y. After installation, the command is automatically restarted.
  
  The gcloud services identity command creates or gets the service agent that Spanner can use to access the Cloud KMS key on your behalf.
  
  The service account ID is formatted like an email address:
```
Service identity created: service-xxx@gcp-sa-spanner.iam.gserviceaccount.com
```
2. Grant the Cloud KMS CryptoKey Encrypter/Decrypter(cloudkms.cryptoKeyEncrypterDecrypter) role to the service account for each region (--location) in your Spanner instance configuration. To do so, run the gcloud kms keys add-iam-policybinding command:
```
gcloud kms keys add-iam-policy-binding KMS_KEY \
    --location KMS_KEY_LOCATION \
    --keyring KMS_KEY_RING \
    --project=PROJECT_ID \
    --member serviceAccount:service-xxx@gcp-sa-spanner.iam.gserviceaccount.com \
    --role roles/cloudkms.cryptoKeyEncrypterDecrypter
```
  Here's an example output:
```
Updated IAM policy for key [KMS_KEY]
```
  If you're using multiple Cloud KMS keys to protect your database, run the gcloud kms keys add-iam-policybinding command for all the your keys.
  
  This role ensures that the service account has permission to both encrypt and decrypt with the Cloud KMS key. For more information, see Cloud KMS permissions and roles.
Create the database and specify your Cloud KMS key.

Console

Use the console to create databases in regional instance configurations.

In the Google Cloud console, go to the Instances page.

Go to Spanner Instances
Click the instance where you want to create a database.
Click Create database and fill out the required fields.
Click Show encryption options.
Select Cloud KMS key.
Select a key from the drop-down list.

The list of keys is limited to the current Google Cloud project. To use a key from a different Google Cloud project, create the database using gcloud CLI instead of the Google Cloud console.

Once the database is created, you can verify that the database is CMEK-enabled by viewing the Database overview page.

gcloud

To create a CMEK-enabled database in a regional, custom, or multi-region instance configuration, run the gcloud spanner databases create command:

gcloud spanner databases create DATABASE \
  --project=SPANNER_PROJECT_ID \
  --instance=INSTANCE_ID \
  --ddl="CREATE TABLE Users (Id INT64 NOT NULL, FirstName STRING(100) NOT NULL, LastName STRING(100) NOT NULL,) PRIMARY KEY (Id)" \
  --kms-project=KMS_PROJECT_ID \
  --kms-location=KMS_KEY_LOCATION \
  --kms-keyring=KMS_KEYRING \
  --kms-keys=KMS_KEY_1[, KMS_KEY_2 ... ]

To verify that a database is CMEK-enabled, run the gcloud spanner databases describe command:

gcloud spanner databases describe DATABASE \
  --project=SPANNER_PROJECT_ID \
  --instance=INSTANCE_ID

CMEK-enabled databases include a field for encryptionConfig, as shown in the following example output:

encryptionConfig:
  kmsKeyNames:projects/my-kms-project/locations/eur5/keyRings/my-kms-key-ring/cryptoKeys/my-kms-key
  name: projects/my-spanner-project/instances/my-instance/databases/my-db
state: READY

Client libraries

C#

To create a CMEK-enabled database in a regional instance configuration:


using Google.Cloud.Spanner.Admin.Database.V1;
using Google.Cloud.Spanner.Common.V1;
using System;
using System.Threading.Tasks;

public class CreateDatabaseWithEncryptionKeyAsyncSample
{
    public async Task<Database> CreateDatabaseWithEncryptionKeyAsync(string projectId, string instanceId, string databaseId, CryptoKeyName kmsKeyName)
    {
        // Create a DatabaseAdminClient instance that can be used to execute a
        // CreateDatabaseRequest with custom encryption configuration options.
        DatabaseAdminClient databaseAdminClient = DatabaseAdminClient.Create();
        // Define create table statement for table #1.
        var createSingersTable =
        @"CREATE TABLE Singers (
                     SingerId INT64 NOT NULL,
                     FirstName STRING(1024),
                     LastName STRING(1024),
                     ComposerInfo BYTES(MAX)
                 ) PRIMARY KEY (SingerId)";
        // Define create table statement for table #2.
        var createAlbumsTable =
        @"CREATE TABLE Albums (
                     SingerId INT64 NOT NULL,
                     AlbumId INT64 NOT NULL,
                     AlbumTitle STRING(MAX)
                 ) PRIMARY KEY (SingerId, AlbumId),
                 INTERLEAVE IN PARENT Singers ON DELETE CASCADE";

        // Create the CreateDatabase request with encryption configuration and execute it.
        var request = new CreateDatabaseRequest
        {
            ParentAsInstanceName = InstanceName.FromProjectInstance(projectId, instanceId),
            CreateStatement = $"CREATE DATABASE `{databaseId}`",
            ExtraStatements = { createSingersTable, createAlbumsTable },
            EncryptionConfig = new EncryptionConfig
            {
                KmsKeyNameAsCryptoKeyName = kmsKeyName,
            },
        };
        var operation = await databaseAdminClient.CreateDatabaseAsync(request);

        // Wait until the operation has finished.
        Console.WriteLine("Waiting for the operation to finish.");
        var completedResponse = await operation.PollUntilCompletedAsync();
        if (completedResponse.IsFaulted)
        {
            Console.WriteLine($"Error while creating database: {completedResponse.Exception}");
            throw completedResponse.Exception;
        }

        var database = completedResponse.Result;
        Console.WriteLine($"Database {database.Name} created with encryption key {database.EncryptionConfig.KmsKeyName}");

        return database;
    }
}

C++

To create a CMEK-enabled database in a regional instance configuration:

void CreateDatabaseWithEncryptionKey(
    google::cloud::spanner_admin::DatabaseAdminClient client,
    std::string const& project_id, std::string const& instance_id,
    std::string const& database_id,
    google::cloud::KmsKeyName const& encryption_key) {
  google::cloud::spanner::Database database(project_id, instance_id,
                                            database_id);
  google::spanner::admin::database::v1::CreateDatabaseRequest request;
  request.set_parent(database.instance().FullName());
  request.set_create_statement("CREATE DATABASE `" + database.database_id() +
                               "`");
  request.add_extra_statements(R"""(
      CREATE TABLE Singers (
          SingerId   INT64 NOT NULL,
          FirstName  STRING(1024),
          LastName   STRING(1024),
          SingerInfo BYTES(MAX),
          FullName   STRING(2049)
              AS (ARRAY_TO_STRING([FirstName, LastName], " ")) STORED
      ) PRIMARY KEY (SingerId))""");
  request.add_extra_statements(R"""(
      CREATE TABLE Albums (
          SingerId     INT64 NOT NULL,
          AlbumId      INT64 NOT NULL,
          AlbumTitle   STRING(MAX)
      ) PRIMARY KEY (SingerId, AlbumId),
          INTERLEAVE IN PARENT Singers ON DELETE CASCADE)""");
  request.mutable_encryption_config()->set_kms_key_name(
      encryption_key.FullName());
  auto db = client.CreateDatabase(request).get();
  if (!db) throw std::move(db).status();
  std::cout << "Database " << db->name() << " created";
  std::cout << " using encryption key " << encryption_key.FullName();
  std::cout << ".\n";
}

Go

To create a CMEK-enabled database in a regional instance configuration:

import (
	"context"
	"fmt"
	"io"
	"regexp"

	database "cloud.google.com/go/spanner/admin/database/apiv1"
	adminpb "cloud.google.com/go/spanner/admin/database/apiv1/databasepb"
)

func createDatabaseWithCustomerManagedEncryptionKey(ctx context.Context, w io.Writer, db, kmsKeyName string) error {
	// db = `projects/<project>/instances/<instance-id>/database/<database-id>`
	// kmsKeyName = `projects/<project>/locations/<location>/keyRings/<key_ring>/cryptoKeys/<kms_key_name>`
	matches := regexp.MustCompile("^(.+)/databases/(.+)$").FindStringSubmatch(db)
	if matches == nil || len(matches) != 3 {
		return fmt.Errorf("createDatabaseWithCustomerManagedEncryptionKey: invalid database id %q", db)
	}
	instanceName := matches[1]
	databaseId := matches[2]

	adminClient, err := database.NewDatabaseAdminClient(ctx)
	if err != nil {
		return fmt.Errorf("createDatabaseWithCustomerManagedEncryptionKey.NewDatabaseAdminClient: %w", err)
	}
	defer adminClient.Close()

	// Create a database with tables using a Customer Managed Encryption Key
	req := adminpb.CreateDatabaseRequest{
		Parent:          instanceName,
		CreateStatement: "CREATE DATABASE `" + databaseId + "`",
		ExtraStatements: []string{
			`CREATE TABLE Singers (
				SingerId   INT64 NOT NULL,
				FirstName  STRING(1024),
				LastName   STRING(1024),
				SingerInfo BYTES(MAX)
			) PRIMARY KEY (SingerId)`,
			`CREATE TABLE Albums (
				SingerId     INT64 NOT NULL,
				AlbumId      INT64 NOT NULL,
				AlbumTitle   STRING(MAX)
			) PRIMARY KEY (SingerId, AlbumId),
			INTERLEAVE IN PARENT Singers ON DELETE CASCADE`,
		},
		EncryptionConfig: &adminpb.EncryptionConfig{KmsKeyName: kmsKeyName},
	}
	op, err := adminClient.CreateDatabase(ctx, &req)
	if err != nil {
		return fmt.Errorf("createDatabaseWithCustomerManagedEncryptionKey.CreateDatabase: %w", err)
	}
	dbObj, err := op.Wait(ctx)
	if err != nil {
		return fmt.Errorf("createDatabaseWithCustomerManagedEncryptionKey.Wait: %w", err)
	}
	fmt.Fprintf(w, "Created database [%s] using encryption key %q\n", dbObj.Name, dbObj.EncryptionConfig.KmsKeyName)
	return nil
}

Java

To create a CMEK-enabled database in a regional instance configuration:


import com.google.cloud.spanner.Spanner;
import com.google.cloud.spanner.SpannerExceptionFactory;
import com.google.cloud.spanner.SpannerOptions;
import com.google.cloud.spanner.admin.database.v1.DatabaseAdminClient;
import com.google.common.collect.ImmutableList;
import com.google.spanner.admin.database.v1.CreateDatabaseRequest;
import com.google.spanner.admin.database.v1.Database;
import com.google.spanner.admin.database.v1.EncryptionConfig;
import com.google.spanner.admin.database.v1.InstanceName;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

public class CreateDatabaseWithEncryptionKey {

  static void createDatabaseWithEncryptionKey() {
    // TODO(developer): Replace these variables before running the sample.
    String projectId = "my-project";
    String instanceId = "my-instance";
    String databaseId = "my-database";
    String kmsKeyName =
        "projects/" + projectId + "/locations/<location>/keyRings/<keyRing>/cryptoKeys/<keyId>";

    try (Spanner spanner =
        SpannerOptions.newBuilder().setProjectId(projectId).build().getService();
        DatabaseAdminClient adminClient = spanner.createDatabaseAdminClient()) {
      createDatabaseWithEncryptionKey(
          adminClient,
          projectId,
          instanceId,
          databaseId,
          kmsKeyName);
    }
  }

  static void createDatabaseWithEncryptionKey(DatabaseAdminClient adminClient,
      String projectId, String instanceId, String databaseId, String kmsKeyName) {
    InstanceName instanceName = InstanceName.of(projectId, instanceId);
    CreateDatabaseRequest request = CreateDatabaseRequest.newBuilder()
        .setParent(instanceName.toString())
        .setCreateStatement("CREATE DATABASE `" + databaseId + "`")
        .setEncryptionConfig(EncryptionConfig.newBuilder().setKmsKeyName(kmsKeyName).build())
        .addAllExtraStatements(
            ImmutableList.of(
                "CREATE TABLE Singers ("
                    + "  SingerId   INT64 NOT NULL,"
                    + "  FirstName  STRING(1024),"
                    + "  LastName   STRING(1024),"
                    + "  SingerInfo BYTES(MAX)"
                    + ") PRIMARY KEY (SingerId)",
                "CREATE TABLE Albums ("
                    + "  SingerId     INT64 NOT NULL,"
                    + "  AlbumId      INT64 NOT NULL,"
                    + "  AlbumTitle   STRING(MAX)"
                    + ") PRIMARY KEY (SingerId, AlbumId),"
                    + "  INTERLEAVE IN PARENT Singers ON DELETE CASCADE"
            ))
        .build();
    try {
      System.out.println("Waiting for operation to complete...");
      Database createdDatabase =
          adminClient.createDatabaseAsync(request).get(120, TimeUnit.SECONDS);

      System.out.printf(
          "Database %s created with encryption key %s%n",
          createdDatabase.getName(),
          createdDatabase.getEncryptionConfig().getKmsKeyName()
      );
    } catch (ExecutionException e) {
      // If the operation failed during execution, expose the cause.
      throw SpannerExceptionFactory.asSpannerException(e.getCause());
    } catch (InterruptedException e) {
      // Throw when a thread is waiting, sleeping, or otherwise occupied,
      // and the thread is interrupted, either before or during the activity.
      throw SpannerExceptionFactory.propagateInterrupt(e);
    } catch (TimeoutException e) {
      // If the operation timed out propagates the timeout
      throw SpannerExceptionFactory.propagateTimeout(e);
    }
  }
}

Node.js

To create a CMEK-enabled database in a regional instance configuration:


// Imports the Google Cloud client library
const {Spanner, protos} = require('@google-cloud/spanner');

/**
 * TODO(developer): Uncomment the following lines before running the sample.
 */
// const projectId = 'my-project-id';
// const instanceId = 'my-instance';
// const databaseId = 'my-database';
// const keyName =
//   'projects/my-project-id/my-region/keyRings/my-key-ring/cryptoKeys/my-key';

// creates a client
const spanner = new Spanner({
  projectId: projectId,
});

// Gets a reference to a Cloud Spanner Database Admin Client object
const databaseAdminClient = spanner.getDatabaseAdminClient();

// Creates a database
const [operation] = await databaseAdminClient.createDatabase({
  createStatement: 'CREATE DATABASE `' + databaseId + '`',
  parent: databaseAdminClient.instancePath(projectId, instanceId),
  encryptionConfig:
    (protos.google.spanner.admin.database.v1.EncryptionConfig = {
      kmsKeyName: keyName,
    }),
});

console.log(`Waiting for operation on ${databaseId} to complete...`);
await operation.promise();

console.log(`Created database ${databaseId} on instance ${instanceId}.`);

// Get encryption key
const [metadata] = await databaseAdminClient.getDatabase({
  name: databaseAdminClient.databasePath(projectId, instanceId, databaseId),
});

console.log(
  `Database encrypted with key ${metadata.encryptionConfig.kmsKeyName}.`
);

PHP

To create a CMEK-enabled database in a regional instance configuration:

use Google\Cloud\Spanner\Admin\Database\V1\Client\DatabaseAdminClient;
use Google\Cloud\Spanner\Admin\Database\V1\CreateDatabaseRequest;
use Google\Cloud\Spanner\Admin\Database\V1\EncryptionConfig;

/**
 * Creates an encrypted database with tables for sample data.
 * Example:
 * ```
 * create_database_with_encryption_key($projectId, $instanceId, $databaseId, $kmsKeyName);
 * ```
 *
 * @param string $projectId The Google Cloud project ID.
 * @param string $instanceId The Spanner instance ID.
 * @param string $databaseId The Spanner database ID.
 * @param string $kmsKeyName The KMS key used for encryption.
 */
function create_database_with_encryption_key(
    string $projectId,
    string $instanceId,
    string $databaseId,
    string $kmsKeyName
): void {
    $databaseAdminClient = new DatabaseAdminClient();
    $instanceName = DatabaseAdminClient::instanceName($projectId, $instanceId);

    $createDatabaseRequest = new CreateDatabaseRequest();
    $createDatabaseRequest->setParent($instanceName);
    $createDatabaseRequest->setCreateStatement(sprintf('CREATE DATABASE `%s`', $databaseId));
    $createDatabaseRequest->setExtraStatements([
        'CREATE TABLE Singers (
            SingerId     INT64 NOT NULL,
            FirstName    STRING(1024),
            LastName     STRING(1024),
            SingerInfo   BYTES(MAX)
        ) PRIMARY KEY (SingerId)',
        'CREATE TABLE Albums (
            SingerId     INT64 NOT NULL,
            AlbumId      INT64 NOT NULL,
            AlbumTitle   STRING(MAX)
        ) PRIMARY KEY (SingerId, AlbumId),
        INTERLEAVE IN PARENT Singers ON DELETE CASCADE'
    ]);

    if (!empty($kmsKeyName)) {
        $encryptionConfig = new EncryptionConfig();
        $encryptionConfig->setKmsKeyName($kmsKeyName);
        $createDatabaseRequest->setEncryptionConfig($encryptionConfig);
    }

    $operationResponse = $databaseAdminClient->createDatabase($createDatabaseRequest);
    printf('Waiting for operation to complete...' . PHP_EOL);
    $operationResponse->pollUntilComplete();

    if ($operationResponse->operationSucceeded()) {
        $database = $operationResponse->getResult();
        printf(
            'Created database %s on instance %s with encryption key %s' . PHP_EOL,
            $databaseId,
            $instanceId,
            $database->getEncryptionConfig()->getKmsKeyName()
        );
    } else {
        $error = $operationResponse->getError();
        printf('Failed to create encrypted database: %s' . PHP_EOL, $error->getMessage());
    }
}

Python

To create a CMEK-enabled database in a regional instance configuration:

def create_database_with_encryption_key(instance_id, database_id, kms_key_name):
    """Creates a database with tables using a Customer Managed Encryption Key (CMEK)."""
    from google.cloud.spanner_admin_database_v1 import EncryptionConfig
    from google.cloud.spanner_admin_database_v1.types import \
        spanner_database_admin

    spanner_client = spanner.Client()
    database_admin_api = spanner_client.database_admin_api

    request = spanner_database_admin.CreateDatabaseRequest(
        parent=database_admin_api.instance_path(spanner_client.project, instance_id),
        create_statement=f"CREATE DATABASE `{database_id}`",
        extra_statements=[
            """CREATE TABLE Singers (
            SingerId     INT64 NOT NULL,
            FirstName    STRING(1024),
            LastName     STRING(1024),
            SingerInfo   BYTES(MAX)
        ) PRIMARY KEY (SingerId)""",
            """CREATE TABLE Albums (
            SingerId     INT64 NOT NULL,
            AlbumId      INT64 NOT NULL,
            AlbumTitle   STRING(MAX)
        ) PRIMARY KEY (SingerId, AlbumId),
        INTERLEAVE IN PARENT Singers ON DELETE CASCADE""",
        ],
        encryption_config=EncryptionConfig(kms_key_name=kms_key_name),
    )

    operation = database_admin_api.create_database(request=request)

    print("Waiting for operation to complete...")
    database = operation.result(OPERATION_TIMEOUT_SECONDS)

    print(
        "Database {} created with encryption key {}".format(
            database.name, database.encryption_config.kms_key_name
        )
    )

Ruby

To create a CMEK-enabled database in a regional instance configuration:

# project_id  = "Your Google Cloud project ID"
# instance_id = "Your Spanner instance ID"
# database_id = "Your Spanner database ID"
# kms_key_name = "Database eencryption KMS key"

require "google/cloud/spanner"
require "google/cloud/spanner/admin/database"

database_admin_client = Google::Cloud::Spanner::Admin::Database.database_admin

instance_path = database_admin_client.instance_path project: project_id, instance: instance_id

db_path = database_admin_client.database_path project: project_id,
                                              instance: instance_id,
                                              database: database_id

job = database_admin_client.create_database parent: instance_path,
                                            create_statement: "CREATE DATABASE `#{database_id}`",
                                            extra_statements: [
                                              "CREATE TABLE Singers (
                                   SingerId     INT64 NOT NULL,
                                   FirstName    STRING(1024),
                                   LastName     STRING(1024),
                                   SingerInfo   BYTES(MAX)
                                 ) PRIMARY KEY (SingerId)",

                                              "CREATE TABLE Albums (
                                   SingerId     INT64 NOT NULL,
                                   AlbumId      INT64 NOT NULL,
                                   AlbumTitle   STRING(MAX)
                                 ) PRIMARY KEY (SingerId, AlbumId),
                                 INTERLEAVE IN PARENT Singers ON DELETE CASCADE"
                                            ],
                                            encryption_config: { kms_key_name: kms_key_name }

puts "Waiting for create database operation to complete"

job.wait_until_done!
database = database_admin_client.get_database name: db_path

puts "Database #{database_id} created with encryption key #{database.encryption_config.kms_key_name}"

View the key versions in use

The database's encryption_info field shows information about key versions.

When a database's key version changes, the change isn't immediately propagated to encryption_info. There might be a delay before the change is reflected in this field.

Console

In the Google Cloud console, go to the Instances page.

Go to Instances
Click the instance containing the database you want to view.
Click the database.

Encryption information is displayed on the Database details page.

gcloud

You can get a database's encryption_info by running the gcloud spanner databases describe or gcloud spanner databases list command. For example:

gcloud spanner databases describe DATABASE \
    --project=SPANNER_PROJECT_ID \
    --instance=INSTANCE_ID

Here's an example output:

name: projects/my-project/instances/test-instance/databases/example-db
encryptionInfo:
- encryptionType: CUSTOMER_MANAGED_ENCRYPTION
  kmsKeyVersion: projects/my-kms-project/locations/my-kms-key1-location/keyRings/my-kms-key-ring1/cryptoKeys/my-kms-key1/cryptoKeyVersions/1
- encryptionType: CUSTOMER_MANAGED_ENCRYPTION
  kmsKeyVersion: projects/my-kms-project/locations/my-kms-key2-location/keyRings/my-kms-key-ring2/cryptoKeys/my-kms-key2/cryptoKeyVersions/1

Disable the key

Disable the key version(s) that are in use by following these instructions for each key version.
Wait for the change to take effect. Disabling a key can take up to three hours to propagate.
To confirm that the database is no longer accessible, execute a query in the CMEK-disabled database:
```
gcloud spanner databases execute-sql DATABASE \
    --project=SPANNER_PROJECT_ID \
    --instance=INSTANCE_ID \
    --sql='SELECT * FROM Users'
```
The following error message appears: KMS key required by the Spanner resource is not accessible.

Enable the key

Enable the key versions that are in use by the database by following these instructions for each key version.
Wait for the change to take effect. Enabling a key can take up to three hours to propagate.

To confirm that the database is no longer accessible, execute a query in the CMEK-enabled database:

gcloud spanner databases execute-sql DATABASE \
    --project=SPANNER_PROJECT_ID \
    --instance=INSTANCE_ID \
    --sql='SELECT * FROM Users'

If the change has taken effect, the command executes successfully.

Back up a database

You can use Spanner backups to create backups of your databases. By default, Spanner backups created from a database use the same encryption configuration as the database itself. You can optionally specify a different encryption configuration for a backup.

Console

Use the console to create backups in regional instance configurations.

In the Google Cloud console, go to the Instances page.

Go to Spanner Instances
Click the instance name that contains the database that you want to back up.
Click the database.
In the navigation pane, click Backup/Restore.
In the Backups tab, click Create backup.
Enter a backup name and select an expiration date.
Optional: Click Show encryption options.

a. If you want to use a different encryption configuration for your backup, click the slider next to Use existing encryption.

a. Select Cloud KMS key.

a. Select a key from the drop-down list.

The list of keys is limited to the current Google Cloud project. To use a key from a different Google Cloud project, create the database using gcloud CLI instead of the Google Cloud console.
Click Create.

The Backups table displays encryption information for each backup.

Screenshot of the Backups table showing the encryption information for each backup

gcloud

To create a CMEK-enabled backup in a regional, custom, or multi-region instance configuration, run the gcloud spanner backups create command:

gcloud spanner backups create BACKUP \
    --project=SPANNER_PROJECT_ID \
    --instance=INSTANCE_ID \
    --database=DATABASE  \
    --retention-period=RETENTION_PERIOD  \
    --encryption-type=customer_managed_encryption \
    --kms-project=KMS_PROJECT_ID \
    --kms-location=KMS_KEY_LOCATION \
    --kms-keyring=KMS_KEY_RING \
    --kms-keys=KMS_KEY_1[, KMS_KEY_2 ... ]
    --async

To verify that the backup created is CMEK encrypted:

gcloud spanner backups describe BACKUP \
    --project=SPANNER_PROJECT_ID \
    --instance=INSTANCE_ID