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title description author ms.author ms.reviewer ms.date ms.service ms.subservice ms.topic monikerRange
Indexes on enclave-enabled columns with randomized encryption (Tutorial)
Tutorial on how to create and use index on enclave-enabled columns using randomized encryption supported in Always Encrypted with secure enclaves for SQL Server and Azure SQL Database.
jaszymas
jaszymas
vanto
02/03/2025
sql
security
tutorial
>= sql-server-ver15

Tutorial: Create and use indexes on enclave-enabled columns using randomized encryption

[!INCLUDE sqlserver2019-windows-only-asdb]

This tutorial teaches you how to create and use indexes on enclave-enabled columns using randomized encryption supported in Always Encrypted with secure enclaves. It will show you:

[!div class="checklist"]

  • How to create an index when you have access to the keys (the column master key and the column encryption key) protecting the column.
  • How to create an index when you don't have access to the keys protecting the column.

Prerequisites

Download the latest version of SQL Server Management Studio (SSMS).

Make sure you've completed one of the Getting started using Always Encrypted with secure enclaves tutorials before following the below steps in this tutorial.

Step 1: Enable Accelerated Database Recovery (ADR) in your database

Note

This step applies only to [!INCLUDE ssnoversion-md]. If you're using [!INCLUDE ssazure-sqldb] or [!INCLUDEssazuremi-md], skip this step. ADR is always enabled in [!INCLUDE ssazure-sqldb] and [!INCLUDEssazuremi-md].

Microsoft strongly recommends you enable ADR in your database before creating the first index on an enclave-enabled column using randomized encryption. See the Database Recovery section in Always Encrypted with secure enclaves.

  1. Close any SSMS instances you used in the previous tutorial. Closing SSMS will close database connections you've opened, which is required to enable ADR.

  2. Open a new instance of SSMS and connect to your [!INCLUDE ssnoversion-md] instance as sysadmin without Always Encrypted enabled for the database connection.

    1. Start SSMS.
    2. In the Connect to Server dialog, specify your server name, select an authentication method, and specify your credentials.
    3. Select Options >> and select the Always Encrypted tab.
    4. Make sure the Enable Always Encrypted (column encryption) checkbox is not selected.
    5. Select Connect.

  3. Open a new query window and execute the below statement to enable ADR.

    ALTER DATABASE ContosoHR SET ACCELERATED_DATABASE_RECOVERY = ON;

Step 2: Create and test an index without role separation

In this step, you'll create and test an index on an encrypted column. You'll be acting as a single user who is assuming the roles of both a DBA, who manages the database, and the data owner who has access to the keys, protecting the data.

  1. Open a new SSMS instance and connect to your [!INCLUDE ssnoversion-md] instance with Always Encrypted enabled for the database connection.

    1. Start a new instance of SSMS.
    2. In the Connect to Server dialog, specify your server name, select an authentication method, and specify your credentials.
    3. Select Options >> and select the Always Encrypted tab.
    4. Select the checkboxes Enable Always Encrypted (column encryption) and Enable Secure Enclaves
    5. If you're using attestation for your database, select a value of Enclave Attestation Protocol that represents your attestation service (Host Guardian Service or Microsoft Azure Attestation) and fill in the enclave attestation URL. Otherwise, select None.
    6. Select Connect.
    7. If prompted to enable parameterization for Always Encrypted queries, select Enable.

  2. If you weren't prompted to enable Parameterization for Always Encrypted, verify it's enabled.

    1. Select Tools from the main menu of SSMS.
    2. Select Options....
    3. Navigate to Query Execution > SQL Server > Advanced.
    4. Ensure that Enable Parameterization for Always Encrypted is checked.
    5. Select OK.

  3. Open a query window and execute the below statements to encrypt the LastName column in the Employees table. You'll create and use an index on that column in later steps.

    ALTER TABLE [HR].[Employees]
ALTER COLUMN [LastName] [nvarchar](50) COLLATE Latin1_General_BIN2 
ENCRYPTED WITH (COLUMN_ENCRYPTION_KEY = [CEK1], ENCRYPTION_TYPE = Randomized, ALGORITHM = 'AEAD_AES_256_CBC_HMAC_SHA_256') NOT NULL;
GO   
ALTER DATABASE SCOPED CONFIGURATION CLEAR PROCEDURE_CACHE;
GO

  4. Create an index on the LastName column. Since you're connected to the database with Always Encrypted enabled, the client driver inside SSMS transparently provides CEK1 (the column encryption key, protecting the LastName column) to the enclave, which is needed to create the index.

    CREATE INDEX IX_LastName ON [HR].[Employees] ([LastName])
INCLUDE ([EmployeeID], [FirstName], [SSN], [Salary]);
GO

  5. Run a rich query on the LastName column and verify SQL Server uses the index when executing the query.

    1. In the same or a new query window, make sure the Include Live Query Statistics button on the toolbar is on.

    2. Execute the below query.

      DECLARE @LastNamePrefix NVARCHAR(50) = 'Aber%';
SELECT * FROM [HR].[Employees] WHERE [LastName] LIKE @LastNamePrefix;
GO

    3. In the Live Query Statistics tab, observe that the query uses the index.

Step 3: Create an index with role separation

In this step, you'll create an index on an encrypted column, pretending to be two different users. One user is a DBA, who needs to create an index, but doesn't have access to the keys. The other user is a data owner, who has access to the keys.

  1. Using the SSMS instance without Always Encrypted enabled, execute the below statement to drop the index on the LastName column.

    DROP INDEX IX_LastName ON [HR].[Employees]; 
GO

  2. Acting as a data owner (or an application that has access to the keys), populate the cache inside the enclave with CEK1.

    [!NOTE] Unless you have restarted your SQL Server instance after Step 2: Create and test an index without role separation, this step is redundant as the CEK1 is already present in the cache. We have added it to demonstrate how a data owner can provide a key to the enclave, if it is not already present in the enclave.

    1. In the SSMS instance with Always Encrypted enabled, execute the below statements in a query window. The statement sends all enclave-enabled column encryption keys to the enclave. See sp_enclave_send_keys for details.

      EXEC sp_enclave_send_keys;
GO

    2. As an alternative to executing the above stored procedure, you can run a DML query that uses the enclave against the LastName column. This will populate the enclave only with CEK1.

      DECLARE @LastNamePrefix NVARCHAR(50) = 'Aber%';
SELECT * FROM [HR].[Employees] WHERE [LastName] LIKE @LastNamePrefix;
GO

  3. Acting as a DBA, create the index.

    1. In the SSMS instance without Always Encrypted enabled, execute the below statements in a query window.

      CREATE INDEX IX_LastName ON [HR].[Employees] ([LastName])
INCLUDE ([EmployeeID], [FirstName], [SSN], [Salary]);
GO

  4. As a data owner, run a rich query on the LastName column and verify SQL Server uses the index when executing the query.

    1. In the SSMS instance with Always Encrypted enabled, select an existing query window or open a new query window, and make sure the Include Live Query Statistics button on the toolbar is on.

    2. Execute the below query.

      DECLARE @LastNamePrefix NVARCHAR(50) = 'Aber%';
SELECT * FROM [HR].[Employees] WHERE [LastName] LIKE @LastNamePrefix;
GO

    3. In the Live Query Statistics, observe that the query uses the index.

Next steps

See also