After the database instance is shut
down and restarted, you need to open the wallet with the alter system command if this task is not
automated otherwise:
SQL> alter system set encryption wallet open identified by "Uni123#Lng";
System altered.
SQL>
Finally, you can easily disable access to all encrypted columns in the database at any time by
closing the wallet:
FIGURE 9-11 Transparent Data Encryption: wallet is open
Chapter 9: Database Security and Auditing 345
SQL> alter system set encryption wallet close;
System altered.
SQL>
Make frequent backups of your wallet and don??™t forget the wallet key (or the security
administrator??”which can be a separate role from the DBA??™s role??”should not forget the wallet
key), because losing the wallet or the password to the wallet will prevent decryption of any
encrypted columns or tablespaces.
Encrypting a Table
You can encrypt a column or columns in one or more tables simply by adding the encrypt
keyword after the column??™s datatype in a create table command or after the column name in
an existing column. For example, to encrypt the SALARY column of the EMPLOYEES table, use
this command:
SQL> alter table employees modify (salary encrypt);
Table altered.
SQL>
Any users who had the privileges to access this column in the past still have the same access
to the SALARY column??”it??™s completely transparent to the users. The only difference is that the
SALARY column is indecipherable to anyone accessing the operating system file containing the
EMPLOYEES table.
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