ecryption_type PLS_INTEGER := SYS.DBMS_CRYPTO.DES_CBC_PKCS5;
    v_key RAW(16) := null;

PROCEDURE setkey (p_key IN VARCHAR2)
    IS
    BEGIN
      IF p_key IS not null THEN
        v_key := UTL_RAW.cast_to_raw(p_key);
       dbms_output.put_line(v_key);
      END IF;
    END setkey;

FUNCTION decrypt( p_data IN RAW ) RETURN VARCHAR2 DETERMINISTIC
    IS
      l_decrypted RAW(32767);
    BEGIN
      l_decrypted := sys.DBMS_CRYPTO.decrypt                              
                      ( src => p_data,
                        typ => ecryption_type,
                        KEY => v_key );

      RETURN UTL_I18N.RAW_TO_CHAR(l_decrypted,'AL32UTF8');
    END decrypt;

execute dbcrypt.setkey('mysecret');  
select dbcrypt.decrypt(encrypted_column) from my_table where rownum < 10;