Published on

February 3, 2006

Exploring SQL Server Encryption Functionality

SQL Server 2005 introduced built-in encryption functionality, making it easier than ever to secure data in SQL Server tables. In this article, we will explore the encryption tools available in SQL Server and how you can use them to your advantage.

Service and Database Master Keys

SQL Server 2005 encryption functionality follows a hierarchical model. At the top of the hierarchy is the Service Master Key (SMK), which is automatically generated at install time. The SMK secures all other keys on the server and can be backed up using the BACKUP SERVICE MASTER KEY statement.

Each SQL database can have its own Database Master Key (DMK), which is created using the CREATE MASTER KEY statement. The DMK is encrypted using the Service Master Key and stored in the master database. It can be backed up using the BACKUP MASTER KEY statement.

Certificates

SQL Server 2005 has the ability to generate self-signed X.509 certificates. Certificates can be created using the CREATE CERTIFICATE statement. They can be used to encrypt and decrypt data directly using the EncryptByCert and DecryptByCert functions.

Certificates can also be used to create symmetric keys for encryption and decryption within the database. The CREATE SYMMETRIC KEY statement is used to create symmetric keys, which can be secured using certificates, passwords, or other keys.

Using Encryption Functions

SQL Server provides a set of functions to encrypt and decrypt data using certificates and symmetric keys. The EncryptByCert and DecryptByCert functions are used to encrypt and decrypt data using certificates. The EncryptByKey and DecryptByKey functions are used to encrypt and decrypt data using symmetric keys.

Here is an example script that demonstrates encryption and decryption using a symmetric key:

-- Create a Symmetric Key
CREATE SYMMETRIC KEY TestSymmetricKey WITH ALGORITHM = TRIPLE_DES ENCRYPTION BY CERTIFICATE TestCertificate;

-- Open the Symmetric Key
OPEN SYMMETRIC KEY TestSymmetricKey DECRYPTION BY CERTIFICATE TestCertificate;

-- Encrypt data using the symmetric key
INSERT INTO MyTable (EncryptedColumn)
VALUES (EncryptByKey(Key_GUID('TestSymmetricKey'), 'SensitiveData'));

-- Decrypt data using the symmetric key
SELECT DecryptByKey(EncryptedColumn) AS DecryptedData
FROM MyTable;

Conclusion

SQL Server 2005’s encryption functionality provides a powerful set of tools for securing sensitive data. By utilizing Service and Database Master Keys, certificates, and symmetric keys, you can enhance the security of your database and application. Understanding how to create, manage, and use these encryption tools is essential for anyone responsible for securing data in SQL Server.

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