Always Encrypted in SQL Server

 Always Encrypted is a feature in SQL Server that ensures sensitive data is never seen in plaintext by the SQL Server instance itself. This feature uses client-side encryption to protect sensitive data. With Always Encrypted, encryption keys are managed by the application, and SQL Server only sees encrypted data.

Steps to Implement Always Encrypted

Prerequisites

• SQL Server 2016 or later.
• SQL Server Management Studio (SSMS) 2016 or later.

Step 1: Create a Column Master Key (CMK)

The CMK is stored in a trusted key store, like the Windows Certificate Store or Azure Key Vault.

USE master;
GO
CREATE COLUMN MASTER KEY [MyCMK]
WITH (
    KEY_STORE_PROVIDER_NAME = N'MSSQL_CERTIFICATE_STORE',
    KEY_PATH = N'CurrentUser/My/CMKCert'
);
GO

Step 2: Create a Column Encryption Key (CEK)

The CEK is used to encrypt the data in the columns and is protected by the CMK.

USE YourDatabase; -- Replace with your database name
GO
CREATE COLUMN ENCRYPTION KEY [MyCEK]
WITH VALUES (
    COLUMN_MASTER_KEY = [MyCMK],
    ALGORITHM = N'RSA_OAEP',
    ENCRYPTED_VALUE = 0x<encrypted_value>
);
GO

Step 3: Encrypt Columns

When creating or altering tables, specify the encryption for the columns.

CREATE TABLE CustomerData (
    CustomerID INT PRIMARY KEY,
    SSN CHAR(11) COLLATE Latin1_General_BIN2 ENCRYPTED WITH (
        COLUMN_ENCRYPTION_KEY = MyCEK,
        ENCRYPTION_TYPE = Deterministic,
        ALGORITHM = 'AEAD_AES_256_CBC_HMAC_SHA_256'
    )
);
GO

Step 4: Insert Encrypted Data

To insert data into an encrypted column, you need to use an application or SSMS configured with the Always Encrypted feature.

INSERT INTO CustomerData (CustomerID, SSN)
VALUES (1, '123-45-6789');
GO

Step 5: Query Encrypted Data

To query encrypted data, use an application or SSMS configured with the Always Encrypted feature.

SELECT CustomerID, SSN
FROM CustomerData;
GO

Full Example Script

Here is the full script combining all the steps:

-- Step 1: Create a Column Master Key (CMK)
USE master;
GO
CREATE COLUMN MASTER KEY [MyCMK]
WITH (
    KEY_STORE_PROVIDER_NAME = N'MSSQL_CERTIFICATE_STORE',
    KEY_PATH = N'CurrentUser/My/CMKCert'
);
GO

-- Step 2: Create a Column Encryption Key (CEK)
USE YourDatabase; -- Replace with your database name
GO
CREATE COLUMN ENCRYPTION KEY [MyCEK]
WITH VALUES (
    COLUMN_MASTER_KEY = [MyCMK],
    ALGORITHM = N'RSA_OAEP',
    ENCRYPTED_VALUE = 0x<encrypted_value> -- Replace with your encrypted value
);
GO

-- Step 3: Encrypt Columns
CREATE TABLE CustomerData (
    CustomerID INT PRIMARY KEY,
    SSN CHAR(11) COLLATE Latin1_General_BIN2 ENCRYPTED WITH (
        COLUMN_ENCRYPTION_KEY = MyCEK,
        ENCRYPTION_TYPE = Deterministic,
        ALGORITHM = 'AEAD_AES_256_CBC_HMAC_SHA_256'
    )
);
GO

-- Step 4: Insert Encrypted Data
-- This step requires the Always Encrypted feature enabled in the client application or SSMS
INSERT INTO CustomerData (CustomerID, SSN)
VALUES (1, '123-45-6789');
GO

-- Step 5: Query Encrypted Data
-- This step requires the Always Encrypted feature enabled in the client application or SSMS
SELECT CustomerID, SSN
FROM CustomerData;
GO

Configuration in SQL Server Management Studio (SSMS)

1. Enable Always Encrypted: Ensure the Always Encrypted feature is enabled in SSMS.
2. Encrypt Columns: Use the "Encrypt Columns" wizard in SSMS to encrypt existing columns.
3. Data Access: Ensure your application or SSMS is configured to use the Always Encrypted driver for accessing encrypted data.

Key Management

• Backup Keys: Always back up your CMKs and CEKs securely. Without these keys, you cannot decrypt your data.
• Key Rotation: Regularly rotate encryption keys to maintain security.

Security Considerations

• Client Application: Ensure your client application is secure and handles encryption keys properly.
• Performance: Always Encrypted can impact performance, especially for large datasets. Test your implementation to ensure it meets your performance requirements.

By following these steps, you can implement Always Encrypted in SQL Server to protect sensitive data, ensuring that it is always encrypted and never visible to unauthorized users, including DBAs.

Transparent Data Encryption (TDE)
Column-Level Encryption
Always Encrypted
Dynamic Data Masking (DDM)
Transport Layer Security (TLS)