Shell Programming and Scripting

Hello All,
i work with backup, The below script runs and tar the user specified dir and put it in a backup machine. can any one help me to modify this in such a was that the tar file generated can be given a users specific password so that it can have high security.
KINDLY LET ME KNOW IF IT IS NOT CLEAR OR YOU WANT ANYOTHER INFORMATION.

#function to tar the files
tar_it ()
{
#echo "Taring $FILELIST\n"
if [ $TAR_NO -gt 0 ]
then
$TAR rvpf ${BCKDATDIR}${USERNAME}/${TARFILE} $FILELIST 2>&1 | tee -a $TARLOG
TAR_NO=`expr $TAR_NO + 1`
else

OLDTARFILE=`echo $TARFILE |awk -F"_" '{print $1}'`
if [ ! -z "$OLDTARFILE" ]
then
rm -f ${BCKDATDIR}${USERNAME}/*
fi
$TAR cvpf ${BCKDATDIR}${USERNAME}/${TARFILE} $FILELIST 2>&1 | tee -a $TARLOG
TAR_NO=`expr $TAR_NO + 1`
fi
}

...................
HOST_NAME=${LOCAL_MACH}#function to tar the files
tar_it ()
{
#echo "Taring $FILELIST\n"
if [ $TAR_NO -gt 0 ]
then
$TAR rvpf ${BCKDATDIR}${USERNAME}/${TARFILE} $FILELIST 2>&1 | tee -a $TARLOG
TAR_NO=`expr $TAR_NO + 1`
else

OLDTARFILE=`echo $TARFILE |awk -F"_" '{print $1}'`
if [ ! -z "$OLDTARFILE" ]
then
rm -f ${BCKDATDIR}${USERNAME}/*
fi
$TAR cvpf ${BCKDATDIR}${USERNAME}/${TARFILE} $FILELIST 2>&1 | tee -a $TARLOG
TAR_NO=`expr $TAR_NO + 1`
fi
}

What about unix crypt ?

Code:

 cat  tarfilename | crypt my_keys > tarfilename.sec  ; # to scramble
 cat  tarfilename.sec  | crypt my_keys > tarfilename ; # to un-scramble

Hello andryk,
Thanks a lot it helped.

Regards,
Pradeep