Simple Encryption Example

#  Enter four-digit number and Perform Encryption
# e.g. 5678 will be displayed as 4321 Rule : 9-5 = 4, 9-6=3, 9-7=2,9-8=1 i.e. 4321

#!/bin/bash
#set -x

echo "Enter your no"
read myno
revno=0
while [ $myno -gt 0 ] ;
do
digit=`expr $myno % 10`
myno=`expr $myno / 10`
encodeno=`expr 9 - $digit`
revno=`expr $encodeno + $revno \* 10`
done

echo $revno | rev