You can encrypt any permanent tablespace to protect sensitive data. Tablespace encryption is completely transparent to your applications, so no application modification is necessary. Encrypted tablespaces primarily protect your data from unauthorized access by means other than through the database. For example, when encrypted tablespaces are written to backup media for travel from one Oracle database to another or for travel to an off-site facility for storage, they remain encrypted. Also, encrypted tablespaces protect data from users who try to circumvent the security features of the database and access database files directly through the operating system file system.
Tablespace encryption does not address all security issues. It does not, for example, provide access control from within the database. Any user who is granted privileges on objects stored in an encrypted tablespace can access those objects without providing any kind of additional password or key.
When you encrypt a tablespace, all tablespace blocks are encrypted. All segment types are supported for encryption, including tables, clusters, indexes, LOBs (BASICFILE and SECUREFILE), table and index partitions, and so on.
There is no need to use LOB encryption on SECUREFILE LOBs stored in an encrypted tablespace.
To maximize security, data from an encrypted tablespace is automatically encrypted when written to the undo tablespace, to the redo logs, and to any temporary tablespace. There is no need to explicitly create encrypted undo or temporary tablespaces, and in fact, you cannot specify encryption for those tablespace types.
For partitioned tables and indexes that have different partitions in different tablespaces, it is permitted to use both encrypted and non-encrypted tablespaces in the same table or index.
Tablespace encryption uses the transparent data encryption feature of Oracle Database, which requires that you create an Oracle wallet to store the master encryption key for the database. The wallet must be open before you can create the encrypted tablespace and before you can store or retrieve encrypted data. When you open the wallet, it is available to all session, and it remains open until you explicitly close it or until the database is shut down.
To encrypt a tablespace, you must open the database with the COMPATIBLE initialization parameter set to 11.1.0 or higher. The default setting for COMPATIBLE for a new Oracle Database 11g Release 2 installation is 11.2.0. Any user who can create a tablespace can create an encrypted tablespace.
Transparent data encryption supports industry-standard encryption algorithms, including the following Advanced Encryption Standard (AES) and Triple Data Encryption Standard (3DES) algorithms:
The encryption key length is implied by the algorithm name. For example, the AES128 algorithm uses 128-bit keys. You specify the algorithm to use when you create the tablespace, and different tablespaces can use different algorithms. Although longer key lengths theoretically provide greater security, there is a trade-off in CPU overhead. If you do not specify the algorithm in your CREATE TABLESPACE statement, AES128 is the default. There is no disk space overhead for encrypting a tablespace.
The following statement creates an encrypted tablespace with the default encryption algorithm:
CREATE TABLESPACE securespaceDATAFILE '/u01/app/oracle/oradata/orcl/secure01.dbf' SIZE 100MENCRYPTIONDEFAULT STORAGE(ENCRYPT);
The following statement creates the same tablespace with the AES256 algorithm:
CREATE TABLESPACE securespaceDATAFILE '/u01/app/oracle/oradata/orcl/secure01.dbf' SIZE 100MENCRYPTION USING 'AES256'DEFAULT STORAGE(ENCRYPT);
The following are restrictions for encrypted tablespaces:
You cannot encrypt an existing tablespace with an ALTER TABLESPACE statement. However, you can use Data Pump or SQL statements such as CREATE TABLE AS SELECT or ALTER TABLE MOVE to move existing table data into an encrypted tablespace.
Encrypted tablespaces are subject to restrictions when transporting to another database. See "Limitations on Transportable Tablespace Use".
When recovering a database with encrypted tablespaces (for example after a SHUTDOWN ABORT or a catastrophic error that brings down the database instance), you must open the Oracle wallet after database mount and before database open, so the recovery process can decrypt data blocks and redo.
In addition, see Oracle Database Advanced Security Administrator's Guide for general restrictions for transparent data encryption.
Querying Tablespace Encryption Information
The DBA_TABLESPACES and USER_TABLESPACES data dictionary views include a column named ENCRYPTED. This column contains YES for encrypted tablespaces.
The view V$ENCRYPTED_TABLESPACES lists all currently encrypted tablespaces. The following query displays the name and encryption algorithm of encrypted tablespaces:
SELECT t.name, e.encryptionalg algorithm FROM v$tablespace t, v$encrypted_tablespaces eWHERE t.ts# = e.ts#; NAME ALGORITHM ------------------------------ --------- SECURESPACE AES256收起