The following illustration shows the architecture of TDE encryption. A new key, used only for TDE and referred to as the database encryption key (DEK), is created and stored in the user database. When you use TDE, the DMK and certificate must be stored in the master database. TDE uses a similar hierarchy down to the certificate. These keys, in turn, protect symmetric keys, which protect the data. The SMK protects the database master key (DMK), which is stored at the user database level and protects certificates and asymmetric keys. The Windows Data Protection API (DPAPI) is at the root of the encryption tree, secures the key hierarchy at the machine level, and is used to protect the service master key (SMK) for the database server instance. You can still use a certificate that exceeds its expiration date to encrypt and decrypt data with TDE. You also might need the certificate for some operations until you do a full database backup. Although the database isn't encrypted, parts of the transaction log might remain protected. Keep the encrypting certificate even if you've disabled TDE on the database. If the certificate becomes unavailable, or if you restore or attach the database on another server, you need backups of the certificate and private key. For more information about certificates, see SQL Server Certificates and Asymmetric Keys.Īfter you enable TDE, immediately back up the certificate and its associated private key. Information applicable to SQL ServerĪfter you secure a database, you can restore it by using the correct certificate. For more information on using TDE with SQL Database, see transparent data encryption with Azure SQL Database. To move a TDE database on SQL Database, you don't have to decrypt the database for the move operation. When you use TDE with Azure SQL Database, SQL Database automatically creates the server-level certificate stored in the master database. TDE doesn't increase the size of the encrypted database. The pages in an encrypted database are encrypted before they're written to disk and are decrypted when read into memory. The SQL Server Security Blog on TDE with FAQĮncryption of a database file is done at the page level.Use SQL Server Connector with SQL Encryption Features.Move a TDE Protected Database to Another SQL Server.Get started with transparent data encryption (TDE) in Azure Synapse Analytics.Transparent data encryption for SQL Database, SQL Managed Instance, and Azure Synapse Analytics.For more information about how to encrypt data across communication channels, see Enable Encrypted Connections to the Database Engine (SQL Server Configuration Manager). TDE doesn't provide encryption across communication channels. tempdb is automatically encrypted when a user database enabled TDE, but can't be encrypted directly. It can't be used to encrypt master, model, or msdb. TDE isn't available for system databases. This ability lets software developers encrypt data by using AES and 3DES encryption algorithms without changing existing applications. It lets you follow many laws, regulations, and guidelines established in various industries. TDE protects data at rest, which is the data and log files. The DEK is a symmetric key, and is secured by a certificate that the server's master database stores or by an asymmetric key that an EKM module protects. The database boot record stores the key for availability during recovery. The encryption uses a database encryption key (DEK). TDE does real-time I/O encryption and decryption of data and log files. But you must plan this kind of protection in advance. This solution prevents anyone without the keys from using the data. One solution is to encrypt sensitive data in a database and use a certificate to protect the keys that encrypt the data. However, a malicious party who steals physical media like drives or backup tapes can restore or attach the database and browse its data.
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