How to: Encrypt a Column of Data
This topic shows two ways that you can encrypt a column of data by using symmetric encryption. In the following examples, the plaintext original remains unchanged in the table. This preserves the functionality of the AdventureWorks sample database, and enables you to experiment with the functionality demonstrated in these examples. In a deployment environment, only the encrypted data is stored.
Note
Encryption using AES is not supported on Windows XP or Windows Server 2000. Before running these code examples on a system that does not support AES, you should change "AES_256" to "DES".
Examples
A. Simple symmetric encryption
The following code shows how to encrypt a column by using a symmetric key.
USE AdventureWorks;
GO
--If there is no master key, create one now.
IF NOT EXISTS
(SELECT * FROM sys.symmetric_keys WHERE symmetric_key_id = 101)
CREATE MASTER KEY ENCRYPTION BY
PASSWORD = '23987hxJKL969#ghf0%94467GRkjg5k3fd117r$$#1946kcj$n44nhdlj'
GO
CREATE CERTIFICATE HumanResources037
WITH SUBJECT = 'Employee Social Security Numbers';
GO
CREATE SYMMETRIC KEY SSN_Key_01
WITH ALGORITHM = AES_256
ENCRYPTION BY CERTIFICATE HumanResources037;
GO
USE [AdventureWorks];
GO
-- Create a column in which to store the encrypted data.
ALTER TABLE HumanResources.Employee
ADD EncryptedNationalIDNumber varbinary(128);
GO
-- Open the symmetric key with which to encrypt the data.
OPEN SYMMETRIC KEY SSN_Key_01
DECRYPTION BY CERTIFICATE HumanResources037;
-- Encrypt the value in column NationalIDNumber with symmetric
-- key SSN_Key_01. Save the result in column EncryptedNationalIDNumber.
UPDATE HumanResources.Employee
SET EncryptedNationalIDNumber = EncryptByKey(Key_GUID('SSN_Key_01'), NationalIDNumber);
GO
-- Verify the encryption.
-- First, open the symmetric key with which to decrypt the data.
OPEN SYMMETRIC KEY SSN_Key_01
DECRYPTION BY CERTIFICATE HumanResources037;
GO
-- Now list the original ID, the encrypted ID, and the
-- decrypted ciphertext. If the decryption worked, the original
-- and the decrypted ID will match.
SELECT NationalIDNumber, EncryptedNationalIDNumber
AS 'Encrypted ID Number',
CONVERT(nvarchar, DecryptByKey(EncryptedNationalIDNumber))
AS 'Decrypted ID Number'
FROM HumanResources.Employee;
GO
B. Symmetric encryption that includes an authenticator
The following code shows how to encrypt a column by using symmetric encryption that includes an authenticator.
USE AdventureWorks;
--If there is no master key, create one now.
IF NOT EXISTS
(SELECT * FROM sys.symmetric_keys WHERE symmetric_key_id = 101)
CREATE MASTER KEY ENCRYPTION BY
PASSWORD = '23987hxJKL95QYV4369#ghf0%lekjg5k3fd117r$$#1946kcj$n44ncjhdlj'
GO
CREATE CERTIFICATE Sales09
WITH SUBJECT = 'Customer Credit Card Numbers';
GO
CREATE SYMMETRIC KEY CreditCards_Key11
WITH ALGORITHM = AES_256
ENCRYPTION BY CERTIFICATE Sales09;
GO
-- Create a column in which to store the encrypted data.
ALTER TABLE Sales.CreditCard
ADD CardNumber_Encrypted varbinary(128);
GO
-- Open the symmetric key with which to encrypt the data.
OPEN SYMMETRIC KEY CreditCards_Key11
DECRYPTION BY CERTIFICATE Sales09;
-- Encrypt the value in column CardNumber using the
-- symmetric key CreditCards_Key11.
-- Save the result in column CardNumber_Encrypted.
UPDATE Sales.CreditCard
SET CardNumber_Encrypted = EncryptByKey(Key_GUID('CreditCards_Key11')
, CardNumber, 1, HashBytes('SHA1', CONVERT( varbinary
, CreditCardID)));
GO
-- Verify the encryption.
-- First, open the symmetric key with which to decrypt the data.
OPEN SYMMETRIC KEY CreditCards_Key11
DECRYPTION BY CERTIFICATE Sales09;
GO
-- Now list the original card number, the encrypted card number,
-- and the decrypted ciphertext. If the decryption worked,
-- the original number will match the decrypted number.
SELECT CardNumber, CardNumber_Encrypted
AS 'Encrypted card number', CONVERT(nvarchar,
DecryptByKey(CardNumber_Encrypted, 1 ,
HashBytes('SHA1', CONVERT(varbinary, CreditCardID))))
AS 'Decrypted card number' FROM Sales.CreditCard;
GO
See Also