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Replicate Data in Encrypted Columns (SQL Server Management Studio)

Replication enables you to publish encrypted column data. To decrypt and use this data at the Subscriber, the key that was used to encrypt the data at the Publisher must also be present on the Subscriber. Replication does not provide a secure mechanism to transport encryption keys. You must manually re-create the encryption key at the Subscriber. This topic shows you how to encrypt a column at the Publisher and make sure that the encryption key is available at the Subscriber.

The basic steps are as follows:

  1. Create the symmetric key at the Publisher.

  2. Encrypt column data with the symmetric key.

  3. Publish the table with the encrypted column.

  4. Subscribe to the publication.

  5. Initialize the subscription.

  6. Recreate the symmetric key at the Subscriber using same values for ALGORITHM, KEY_SOURCE, and IDENTITY_VALUE as in step 1.

  7. Access the encrypted column data.

Note Note

You should use a symmetric key to encrypt column data. The symmetric key itself can be secured by different means at the Publisher and Subscriber.

To create and replicate encrypted column data

  1. At the Publisher, execute CREATE SYMMETRIC KEY.

    Security note Security Note

    The value of KEY_SOURCE is valuable data that can be used to re-create the symmetric key and decrypt data. KEY_SOURCE must always be stored and transported securely.

  2. Execute OPEN SYMMETRIC KEY to open the new key.

  3. Use the EncryptByKey function to encrypt column data at the Publisher.

  4. Execute CLOSE SYMMETRIC KEY to close the key.

  5. Publish the table that contains the encrypted column. For more information, see Create a Publication.

  6. Subscribe to the publication. For more information, see Create a Pull Subscription or Create a Push Subscription.

  7. Initialize the subscription. For more information, see Create and Apply the Initial Snapshot.

  8. At the Subscriber, execute CREATE SYMMETRIC KEY using the same values for ALGORITHM, KEY_SOURCE, and IDENTITY_VALUE as in step 1. You can specify a different value for ENCRYPTION BY.

    Security note Security Note

    The value of KEY_SOURCE is valuable data that can be used to re-create the symmetric key and decrypt data. KEY_SOURCE must always be stored and transported securely.

  9. Execute OPEN SYMMETRIC KEY to open the new key.

  10. Use the DecryptByKey function to decrypt replicated data at the Subscriber.

  11. Execute CLOSE SYMMETRIC KEY to close the key.

This example creates a symmetric key, a certificate that is used to help secure the symmetric key, and a master key. These keys are created in the publication database. They are then used to create an encrypted column (EncryptedCreditCardApprovalCode) in the SalesOrderHeader table. This column is published in the AdvWorksSalesOrdersMerge publication instead of the unencrypted CreditCardApprovalCode column. When possible, prompt users to enter security credentials at runtime. If you must store credentials in a script file, you must secure the file to prevent unauthorized access.

-- Execute at the Publisher on the publication database.
USE AdventureWorks2012;
GO

-- Create the database master key if it doesn't exist.
IF NOT EXISTS (SELECT * FROM sys.symmetric_keys 
	WHERE [name] LIKE '%DatabaseMasterKey%')
CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'Pub$p@55w0Rd';

-- Create the cert_keyProtection certificate if it doesn't exist.
IF NOT EXISTS (SELECT * FROM sys.certificates 
	WHERE [name] = 'cert_keyPublisher')
CREATE CERTIFICATE [cert_keyPublisher] 
	WITH SUBJECT = 'Publisher Key Protection';

-- Create the key_ReplDataShare symmetric key if it doesn't exist.
IF NOT EXISTS (SELECT * FROM sys.symmetric_keys 
	WHERE [name] = 'key_ReplDataShare')
CREATE SYMMETRIC KEY [key_ReplDataShare] WITH
    KEY_SOURCE = 'My key generation bits. This is a shared secret!',
    ALGORITHM = AES_256, 
    IDENTITY_VALUE = 'Key Identity generation bits. Also a shared secret'
    ENCRYPTION BY CERTIFICATE [cert_keyPublisher];
GO 

-- Open the encryption key.
OPEN SYMMETRIC KEY [key_ReplDataShare]
    DECRYPTION BY CERTIFICATE [cert_keyPublisher];
GO

-- Create a new CreditCardApprovalCode column in the SalesOrderHeader table.
ALTER TABLE Sales.SalesOrderHeader 
	ADD EncryptedCreditCardApprovalCode VARBINARY(256) NULL;
GO

-- Insert encrypted data from the CreditCardApprovalCode column.
UPDATE Sales.SalesOrderHeader
SET EncryptedCreditCardApprovalCode
    = EncryptByKey(Key_GUID('key_DataShare'), CreditCardApprovalCode);
GO

CLOSE SYMMETRIC KEY [key_ReplDataShare];
GO
DECLARE @publication AS sysname;
DECLARE @table1 AS sysname;
DECLARE @table2 AS sysname;
DECLARE @table3 AS sysname;
DECLARE @salesschema AS sysname;
DECLARE @hrschema AS sysname;
DECLARE @filterclause AS nvarchar(1000);
SET @publication = N'AdvWorksSalesOrdersMerge'; 
SET @table1 = N'Employee'; 
SET @table2 = N'SalesOrderHeader'; 
SET @table3 = N'SalesOrderDetail'; 
SET @salesschema = N'Sales';
SET @hrschema = N'HumanResources';
SET @filterclause = N'Employee.LoginID = HOST_NAME()';

-- Add a filtered article for the Employee table.
EXEC sp_addmergearticle 
  @publication = @publication, 
  @article = @table1, 
  @source_object = @table1, 
  @type = N'table', 
  @source_owner = @hrschema,
  @schema_option = 0x0004CF1,
  @description = N'article for the Employee table',
  @subset_filterclause = @filterclause;

-- Add an article for the SalesOrderHeader table that is filtered
-- based on Employee and horizontally filtered.
EXEC sp_addmergearticle 
  @publication = @publication, 
  @article = @table2, 
  @source_object = @table2, 
  @type = N'table', 
  @source_owner = @salesschema, 
  @vertical_partition = N'true',
  @schema_option = 0x0034EF1,
  @description = N'article for the SalesOrderDetail table';

-- Add an article for the SalesOrderDetail table that is filtered
-- based on SaledOrderHeader.
EXEC sp_addmergearticle 
  @publication = @publication, 
  @article = @table3, 
  @source_object = @table3, 
  @source_owner = @salesschema,
  @description = 'article for the SalesOrderHeader table', 
  @identityrangemanagementoption = N'auto', 
  @pub_identity_range = 100000, 
  @identity_range = 100, 
  @threshold = 80,
  @schema_option = 0x0004EF1;

-- Add all columns to the SalesOrderHeader article.
EXEC sp_mergearticlecolumn 
  @publication = @publication, 
  @article = @table2, 
  @force_invalidate_snapshot = 1, 
  @force_reinit_subscription = 1;

-- Remove the credit card Approval Code column.
EXEC sp_mergearticlecolumn 
  @publication = @publication, 
  @article = @table2, 
  @column = N'CreditCardApprovalCode', 
  @operation = N'drop', 
  @force_invalidate_snapshot = 1, 
  @force_reinit_subscription = 1;

-- Add a merge join filter between Employee and SalesOrderHeader.
EXEC sp_addmergefilter 
  @publication = @publication, 
  @article = @table2, 
  @filtername = N'SalesOrderHeader_Employee', 
  @join_articlename = @table1, 
  @join_filterclause = N'Employee.BusinessEntityID = SalesOrderHeader.SalesPersonID', 
  @join_unique_key = 1, 
  @filter_type = 1, 
  @force_invalidate_snapshot = 1, 
  @force_reinit_subscription = 1;

-- Add a merge join filter between SalesOrderHeader and SalesOrderDetail.
EXEC sp_addmergefilter 
  @publication = @publication, 
  @article = @table3, 
  @filtername = N'SalesOrderDetail_SalesOrderHeader', 
  @join_articlename = @table2, 
  @join_filterclause = N'SalesOrderHeader.SalesOrderID = SalesOrderDetail.SalesOrderID', 
  @join_unique_key = 1, 
  @filter_type = 1, 
  @force_invalidate_snapshot = 1, 
  @force_reinit_subscription = 1;
GO

This example recreates the same symmetric key in the subscription database using the same values for ALGORITHM, KEY_SOURCE, and IDENTITY_VALUE from the first example. This example assumes that you have already initialized a subscription to the AdvWorksSalesOrdersMerge publication to replicate the encrypted column. When possible, prompt users to enter security credentials at runtime. If you must store credentials in a script file, you must secure the file during storage and transport to prevent unauthorized access.

-- Execute at the Subscription on the subscription database.
USE AdventureWorks2012Replica;
GO

-- Create the database master key if it doesn't exist.
IF NOT EXISTS (SELECT * FROM sys.symmetric_keys 
	WHERE [name] LIKE '%DatabaseMasterKey%')
CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'Sub$p@55w0Rd';

-- Create the cert_keySubscriber certificate if it doesn't exist.
-- This can be a different certificate than at the Publisher.
IF NOT EXISTS (SELECT * FROM sys.certificates 
	WHERE [name] = 'cert_keySubscriber')
CREATE CERTIFICATE [cert_keySubscriber] 
	WITH SUBJECT = 'Subscriber Key Protection';

-- Create the key_DataShare symmetric key if it doesn't exist.
IF NOT EXISTS (SELECT * FROM sys.symmetric_keys 
	WHERE [name] = 'key_ReplDataShare')
CREATE SYMMETRIC KEY [key_ReplDataShare] WITH
    KEY_SOURCE = 'My key generation bits. This is a shared secret!',
    ALGORITHM = AES_256, 
    IDENTITY_VALUE = 'Key Identity generation bits. Also a shared secret'
    ENCRYPTION BY CERTIFICATE [cert_keySubscriber];
GO 

-- Open the encryption key.
OPEN SYMMETRIC KEY [key_ReplDataShare]
    DECRYPTION BY CERTIFICATE [cert_keySubscriber];
GO

-- Return the column that was encrypted at the Publisher and also decrypt it.
SELECT SalesOrderID AS 'Order Number', EncryptedCreditCardApprovalCode AS 'Encrypted Approval Code', 
	CONVERT(VARCHAR(15), DecryptByKey(EncryptedCreditCardApprovalCode)) AS 'Decrypted Approval Code'
FROM Sales.SalesOrderHeader;
GO

CLOSE SYMMETRIC KEY [key_ReplDataShare];
GO

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