What Type of Encryption Can Be Used to Encrypt Data at Rest in an Azure SQL Database?


Scott Campbell

When it comes to securing data at rest in an Azure SQL Database, encryption is a crucial aspect. Encryption ensures that even if unauthorized access to the database occurs, the data remains unreadable and protected.

Azure SQL Database offers different types of encryption options to secure your data at rest. Let’s explore each of these options in detail:

Transparent Data Encryption (TDE):

TDE is a widely used encryption method that encrypts the entire database at rest. It operates at the file level, which means that all data files are encrypted using a symmetric database encryption key (DEK). The DEK itself is protected by a certificate stored in Azure Key Vault or by a Service Managed Key (SMK) created by Azure.

TDE provides automatic encryption and decryption of the entire database without any changes needed to the application code or queries. This makes it an excellent choice for achieving quick and efficient encryption. However, TDE does not provide granular control over individual columns or rows within the database.

Always Encrypted:

If you require more granular control over your encrypted data, Always Encrypted is an excellent option. With Always Encrypted, you can encrypt specific columns containing sensitive data while still allowing operations on those columns without decrypting them.

Always Encrypted uses two types of keys: Column Encryption Keys (CEKs) and Column Master Keys (CMKs). The CEKs encrypt and decrypt the column-level data, while CMKs protect the CEKs themselves. The CMK can be stored in Azure Key Vault or Windows Certificate Store.

This type of encryption ensures that sensitive data remains encrypted throughout its lifecycle, from when it is stored in the database to when it is processed by applications.

Bring Your Own Key (BYOK):

Azure SQL Database also offers the option to bring your own key for data encryption. BYOK allows you to use keys that you manage and control outside of Azure Key Vault. This provides an additional layer of control and security as you have full ownership over the keys used for encryption.

With BYOK, you can import your keys into Azure Key Vault and use them to encrypt your Azure SQL Database. This ensures that even if someone gains unauthorized access to your database, they won’t be able to decrypt the data without the externally managed key.


When it comes to securing data at rest in an Azure SQL Database, there are several encryption options available. Transparent Data Encryption (TDE) offers automatic encryption of the entire database, while Always Encrypted provides granular control over specific columns. Bring Your Own Key (BYOK) allows you to bring your own keys for added security.

Consider your specific requirements and sensitivity of data when choosing the appropriate encryption method. Implementing encryption at rest in your Azure SQL Database is a crucial step towards protecting your data from unauthorized access.

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