SQL> SELECT *
  2  FROM v$version;

BANNER
--------------------------------------------------------

Oracle Database 11g Release 11.2.0.4.0 - Production
PL/SQL Release 11.2.0.4.0 - Production
CORE    11.2.0.4.0      Production
TNS for 32-bit Windows: Version 11.2.0.4.0 - Production
NLSRTL Version 11.2.0.4.0 - Production

SQL>  alter system set encryption wallet open identified by "xxxxxxx";

System altered.

SQL> SELECT * FROM v$option where parameter like  'Transparent Data Encryption%';

PARAMETER
-----------------------------------------------------------
VALUE
-----------------------------------------------------------
Transparent Data Encryption
FALSE

SQL> ALTER TABLE ADMIN.CRYPT_TABLE
  2  MODIFY(NAME  ENCRYPT);
ALTER TABLE ADMIN.CRYPT_TABLE
*
ERROR at line 1:
ORA-00439: feature not enabled: Transparent Data Encryption