Advanced Data Encryption in SQL Server - Always Encrypted and TDE

Introduction

Data security is a critical concern for database administrators. SQL Server offers advanced encryption options such as Always Encrypted and Transparent Data Encryption (TDE) to protect sensitive data. This guide explores these encryption methods with sample code and examples.

1. Always Encrypted

Always Encrypted is a feature that ensures sensitive data remains encrypted throughout its entire lifecycle, even when it's being processed within SQL Server. This is achieved through client-side encryption and key management.

1.1. Setup Always Encrypted

To use Always Encrypted, you need to set up column encryption keys, create encrypted columns, and configure your application to work with encrypted data.

-- Create a column master key
CREATE COLUMN MASTER KEY MyColumnMasterKey
WITH (KEY_STORE_PROVIDER_NAME = 'MSSQL_CSP', KEY_PATH = 'Current User/My/ColumnMasterKey');
-- Create a column encryption key
CREATE COLUMN ENCRYPTION KEY MyColumnEncryptionKey
WITH VALUES
(COLUMN_MASTER_KEY = MyColumnMasterKey, ALGORITHM = 'AEAD_AES_256_CBC_HMAC_SHA_256', ENCRYPTED_VALUE = 0x01...);
-- Encrypt a column
ALTER TABLE MyTable
ADD MyEncryptedColumn NVARCHAR(100) ENCRYPTED WITH (ENCRYPTION_TYPE = DETERMINISTIC, ALGORITHM = 'AEAD_AES_256_CBC_HMAC_SHA_256', COLUMN_ENCRYPTION_KEY = MyColumnEncryptionKey);
    

2. Transparent Data Encryption (TDE)

TDE is a feature that encrypts the entire database, ensuring data at rest is protected. It uses a database encryption key (DEK) and a certificate or asymmetric key to encrypt and decrypt data.

2.1. Enabling TDE

To enable TDE, you need to create a DEK, protect it with a certificate or asymmetric key, and enable TDE for the database.

-- Create a database encryption key
USE YourDatabase;
CREATE DATABASE ENCRYPTION KEY
WITH ALGORITHM = AES_256
ENCRYPTION BY SERVER CERTIFICATE MyCertificate;
-- Enable TDE
ALTER DATABASE YourDatabase
SET ENCRYPTION ON;
    

Conclusion

Advanced data encryption in SQL Server is crucial for securing sensitive information. Always Encrypted and TDE offer different approaches to data encryption, and their use depends on your specific security requirements. By implementing these encryption methods and following best practices, you can protect your data both at rest and during processing.