#!/bin/bash
 
if !(( $# == 2 )); then
	echo "Uso: ${0} [-d|-e] string"
	echo "Encode: ${0} -e string"
	echo "Decode: ${0} -d string"
	exit 2
fi
 
# Decoding
function deTrithemius(){
 
	echo "Decoding ... ${1}"
	hash1="$1"
	table="ABCDEFGHIJKLMNNOPQRSTUVWXYZ"
	i=0
	pos=""
	x=1
 
	while (( x<$( echo "`echo $hash1 | wc -c`+1" | bc ) )); do
 
		letra=`echo $hash1 | cut -c$(echo "${x}"|bc)`
 
		if ( `echo ${letra} | grep "[A-Z]" > /dev/null` ); then
			pos=$(echo "`expr index "${table}" "${letra}"`-${i}" | bc)
 
			while (( pos<=0 )); do
				((pos=$( echo "${pos}+`echo -n $table | wc -c`" | bc ) ))
			done
 
			echo -n "${table}" | cut -c${pos} | tr '\n' '\0'
			(( i+=1 )) 
 
		else
			echo -n "${letra}"
		fi
 
		(( x+=1 ))
	done
 
	echo ""
}
 
# Encoding
function Trithemius(){
 
	echo "Encoding ... ${1}"
        hash1="$1"
        table="ABCDEFGHIJKLMNNOPQRSTUVWXYZ"
        i=0
        pos=""
        x=1
 
        while (( x<$( echo "`echo $hash1 | wc -c`+1" | bc ) )); do
 
                letra=`echo $hash1 | cut -c$(echo "${x}"|bc)`
 
		if ( `echo ${letra} | grep "[A-Z]" > /dev/null` ); then
                        pos=$(echo "`expr index "${table}" "${letra}"`+${i}" | bc)
 
                        while (( pos>`echo -n $table | wc -c` )); do
                                ((pos=${pos}-`echo -n $table | wc -c`))
                        done
 
                        echo -n "${table}" | cut -c${pos} | tr '\n' '\0'
                        (( i+=1 ))
 
                else
                        echo -n "${letra}"
                fi
 
                (( x+=1 ))
        done
 
        echo ""
}
 
typeset -u entrada="${2}"
 
case $1 in
 
	"-d" )	deTrithemius "$entrada"
		;;
 
	"-e" )	Trithemius "$entrada"
		;;
 
	* )	echo "Uso: ${0} [-d|-e] string"
        	echo "Encode: ${0} -e string"
        	echo "Decode: ${0} -d string"
        	exit 2
		;;
 
esac