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Transparent data encryption enables you to
encrypt sensitive data, such as credit card
numbers, stored in table columns. Encrypted data
is transparently decrypted for a database user
who has access to the data. Transparent data
encryption helps protect data stored on media in
the event that the storage media or data file
gets stolen.
About Transparent Data Encryption
Oracle Database 11g uses authentication,
authorization, and auditing mechanisms to secure
data in the database, but not in the operating
system data files where data is stored. To
protect these data files, Oracle Database
provides transparent data encryption.
Transparent data encryption encrypts sensitive
table data stored in data files. To prevent
unauthorized decryption, transparent data
encryption stores the encryption keys in a
security module external to the database.
This section contains the following topics:
� Benefits of Using Transparent Data Encryption
� When to Use Transparent Data Encryption
� How Transparent Data Encryption Works
� Overview of Basic Transparent Data Encryption
Operations
Benefits of
Using Transparent Data Encryption
� As
a security administrator, you can be sure that
sensitive data is safe in case the storage media
or data file gets stolen.
� Implementing transparent data encryption helps
you address security-related regulatory
compliance issues.
� You do not need to create triggers or views to
decrypt data. Data from tables is transparently
decrypted for the database user.
� Database users need not be aware of the fact
that the data they are accessing is stored in
encrypted form. Data is transparently decrypted
for the database users and does not require any
action on their part.
� Applications need not be modified to handle
encrypted data. Data encryption/decryption is
managed by the database.
When to Use
Transparent Data Encryption
Use
transparent data encryption to protect
confidential data, such as credit card and
social security numbers, without having to
manage key storage or create auxiliary tables,
views, and triggers. An application that
processes sensitive data can use this feature to
provide strong data encryption with little or no
change to the application.
Restrictions on Using Transparent Data
Encryption
You
cannot use transparent data encryption to
encrypt columns used in foreign key constraints.
This is because every table has a unique column
encryption key.
Transparent data encryption encrypts and
decrypts data at the SQL layer. Oracle Database
utilities and features that bypass the SQL layer
cannot leverage the services provided by
transparent data encryption. Do not use
transparent data encryption with the following
database features:
� Index types other than B-tree
� Range scan search through an index
� External large objects (BFILE)
� Materialized View Logs
� Synchronous Change Data Capture
� Transportable Tablespaces
� Original import/export utilities
Transparent data encryption protects data stored
on disk/media. It does not protect data in
transit. Use Oracle Advanced Security network
encryption solutions discussed in Chapter 2,
"Configuration and Administration Tools
Overview"to encrypt data over the network.
How Transparent Data Encryption Works
Transparent data encryption is a key-based
access control system. Even if the encrypted
data is retrieved, it cannot be understood until
authorized decryption occurs, which is automatic
for users authorized to access the table.
When a table contains encrypted columns, a
single key is used regardless of the number of
encrypted columns. This key is called the column
encryption key. The column encryption keys for
all tables, containing encrypted columns, are
encrypted with the database server master
encryption key and stored in a dictionary table
in the database. No keys are stored in the
clear.
The master encryption key is stored in an
external security module that is outside the
database and accessible only to the security
administrator. For this external security
module, Oracle uses an Oracle wallet as
described in this chapter. Storing the master
encryption key in this way prevents its
unauthorized use.
Using an external security module separates
ordinary program functions from encryption
operations, making it possible to divide duties
between database administrators and security
administrators. Security is enhanced because the
wallet password can be unknown to the database
administrator, requiring the security
administrator to provide the password.
Overview of Basic
Transparent Data Encryption Operations
To enable
transparent data encryption, you must have the
ALTER SYSTEM privilege and a valid password to
the Oracle wallet. If an Oracle wallet does not
exist, then a new one is created using the
password specified in the SQL command.
To create a new
master key and begin using transparent data
encryption, issue the following command:
ALTER
SYSTEM SET ENCRYPTION KEY IDENTIFIED BY password
Enclose the
password in double quotation marks (" "). This
command generates the database server master
encryption key, which the server uses to encrypt
the column encryption key for each table. No
table columns in the database can be encrypted
until the master key of the server has been set.
The master
encryption key remains accessible to the
database until the database instance is
shutdown. To load the master encryption key
after the database is restarted, use the
following command:
ALTER
SYSTEM SET ENCRYPTION WALLET OPEN IDENTIFIED BY
password
Enclose the
password in double quotation marks (" "). To
create a new table with encrypted columns, use
the CREATE TABLE command in the following form:
CREATE
TABLE table_name ( column_name column_type
ENCRYPT,....);
The ENCRYPT
keyword against a column specifies that the
column should be encrypted.
If an existing
table has columns that require encryption, then
use the ALTER TABLE command in the following
form:
ALTER TABLE
table_name MODIFY ( column_name column_type
ENCRYPT,...);
The ENCRYPT
keyword against a column specifies that the
column should be encrypted.
To disable access
to all encrypted columns in the database, use
the following command:
ALTER
SYSTEM SET ENCRYPTION WALLET CLOSE
The preceding
command disables access to the master key in the
wallet and prevents access to data in the
encrypted columns. You need to open the wallet
again, using the
ALTER
SYSTEM SET WALLET OPEN IDENTIFIED BY password
command, to
re-enable access to the master encryption key.
By:
Tharushi Pushpakumara
Associate Information Security Analyst at Sri Lanka CERT|CC
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