alter-master-key-transact-sql.md

title	ALTER MASTER KEY (Transact-SQL) | Microsoft Docs
ms.custom
ms.date	03/14/2017
ms.prod	sql
ms.prod_service	sql-data-warehouse, database-engine, pdw, sql-database
ms.reviewer
ms.technology	t-sql
ms.topic	language-reference
f1_keywords	ALTER MASTER KEY ALTER_MASTER_KEY_TSQL
dev_langs	TSQL
helpviewer_keywords	REGENERATE phrase ALTER MASTER KEY statement decryption [SQL Server], Database Master Key FORCE option encryption [SQL Server], Database Master Key database master key [SQL Server], modifying cryptography [SQL Server], Database Master Key modifying Database Master Key service master key [SQL Server], modifying DROP ENCRYPTION BY SERVICE MASTER KEY phrase
ms.assetid	8ac501c3-4280-4d5b-b58a-1524fa715b50
author	CarlRabeler
ms.author	carlrab
manager	craigg
monikerRange	>=aps-pdw-2016||=azuresqldb-current||=azure-sqldw-latest||>=sql-server-2016||=sqlallproducts-allversions||>=sql-server-linux-2017||=azuresqldb-mi-current

ALTER MASTER KEY (Transact-SQL)

[!INCLUDEtsql-appliesto-ss2008-asdb-asdw-pdw-md]

Changes the properties of a database master key.

Transact-SQL Syntax Conventions

Syntax

-- Syntax for SQL Server  
  
ALTER MASTER KEY <alter_option>  
  
<alter_option> ::=  
    <regenerate_option> | <encryption_option>  
  
<regenerate_option> ::=  
    [ FORCE ] REGENERATE WITH ENCRYPTION BY PASSWORD = 'password'  
  
<encryption_option> ::=  
    ADD ENCRYPTION BY { SERVICE MASTER KEY | PASSWORD = 'password' }  
    |   
    DROP ENCRYPTION BY { SERVICE MASTER KEY | PASSWORD = 'password' }  

-- Syntax for Azure SQL Database
-- Note: DROP ENCRYPTION BY SERVICE MASTER KEY is not supported on Azure SQL Database.
  
ALTER MASTER KEY <alter_option>  
  
<alter_option> ::=  
    <regenerate_option> | <encryption_option>  
  
<regenerate_option> ::=  
    [ FORCE ] REGENERATE WITH ENCRYPTION BY PASSWORD = 'password'  
  
<encryption_option> ::=  
    ADD ENCRYPTION BY { SERVICE MASTER KEY | PASSWORD = 'password' }  
    |   
    DROP ENCRYPTION BY { PASSWORD = 'password' }  

-- Syntax for Azure SQL Data Warehouse and Parallel Data Warehouse  
  
ALTER MASTER KEY <alter_option>  
  
<alter_option> ::=  
    <regenerate_option> | <encryption_option>  
  
<regenerate_option> ::=  
    [ FORCE ] REGENERATE WITH ENCRYPTION BY PASSWORD ='password'<encryption_option> ::=  
    ADD ENCRYPTION BY SERVICE MASTER KEY   
    |   
    DROP ENCRYPTION BY SERVICE MASTER KEY  

Arguments

PASSWORD ='password'
Specifies a password with which to encrypt or decrypt the database master key. password must meet the Windows password policy requirements of the computer that is running the instance of [!INCLUDEssNoVersion].

Remarks

The REGENERATE option re-creates the database master key and all the keys it protects. The keys are first decrypted with the old master key, and then encrypted with the new master key. This resource-intensive operation should be scheduled during a period of low demand, unless the master key has been compromised.

[!INCLUDEssSQL11] uses the AES encryption algorithm to protect the service master key (SMK) and the database master key (DMK). AES is a newer encryption algorithm than 3DES used in earlier versions. After upgrading an instance of the [!INCLUDEssDE] to [!INCLUDEssSQL11] the SMK and DMK should be regenerated in order to upgrade the master keys to AES. For more information about regenerating the SMK, see ALTER SERVICE MASTER KEY (Transact-SQL).

When the FORCE option is used, key regeneration will continue even if the master key is unavailable or the server cannot decrypt all the encrypted private keys. If the master key cannot be opened, use the RESTORE MASTER KEY statement to restore the master key from a backup. Use the FORCE option only if the master key is irretrievable or if decryption fails. Information that is encrypted only by an irretrievable key will be lost.

The DROP ENCRYPTION BY SERVICE MASTER KEY option removes the encryption of the database master key by the service master key.

ADD ENCRYPTION BY SERVICE MASTER KEY causes a copy of the master key to be encrypted using the service master key and stored in both the current database and in master.

Permissions

Requires CONTROL permission on the database. If the database master key has been encrypted with a password, knowledge of that password is also required.

Examples

The following example creates a new database master key for AdventureWorks and reencrypts the keys below it in the encryption hierarchy.

USE AdventureWorks2012;  
ALTER MASTER KEY REGENERATE WITH ENCRYPTION BY PASSWORD = 'dsjdkflJ435907NnmM#sX003';  
GO  

Examples: [!INCLUDEssSDWfull] and [!INCLUDEssPDW]

The following example creates a new database master key for AdventureWorksPDW2012 and re-encrypts the keys below it in the encryption hierarchy.

USE master;  
ALTER MASTER KEY REGENERATE WITH ENCRYPTION BY PASSWORD = 'dsjdkflJ435907NnmM#sX003';  
GO  

See Also

CREATE MASTER KEY (Transact-SQL)
OPEN MASTER KEY (Transact-SQL)
CLOSE MASTER KEY (Transact-SQL)
BACKUP MASTER KEY (Transact-SQL)
RESTORE MASTER KEY (Transact-SQL)
DROP MASTER KEY (Transact-SQL)
Encryption Hierarchy
CREATE DATABASE (SQL Server Transact-SQL)
Database Detach and Attach (SQL Server)