<?php
/************************************************************************
+----------------------------------------------------------------------+
| mono.php -> Monoalphabetic Substitution |
+----------------------------------------------------------------------+ |
| |
| (c) 2002 by M.Abdullah Khaidar (khaidarmak@yahoo.com) |
| |
| This program is free software. You can redistribute it and/or modify |
| it under the terms of the GNU General Public License as published by |
| the Free Software Foundation; either version 2 of the License. |
| |
+----------------------------------------------------------------------+
************************************************************************/
include "main.php";
$TITLE="Monoalphabetic Substitution Encoder and Decoder";
$HEADTITLE="Monoalphabetic Substitution Encoder and Decoder";
function mono($plain,$key){
$unique_table=1;
$detected_table="";
$from="abcdefghijklmnopqrstuvwxyz";
$cipher="";
if(eregi("--",$key)){
return "error: Empty substitution detected";
}
for($i=0;$i<=25;$i++){
$k=substr($key,$i,1);
$check_table[$i]=$k;
}
for($i=0;$i<=25;$i++){
for($j=$i+1;$j<=25;$j++){
if($check_table[$i]==$check_table[$j]){
$unique_table=0;
$detected_table=$detected_table.ascii_letter($i).ascii_letter($j);
}
}
}
$plain=filter($plain);
$cipher=strtr($plain,$from,$key);
if($unique_table==1){
return $cipher;
}else{
$table_error="error: Same substitution table detected:\n";
for($i=0;$i<strlen($detected_table);$i=$i+2){
$d1=substr($detected_table,$i,1);
$d2=substr($detected_table,$i+1,1);
$table_error=$table_error."table ".$d1." and table ".$d2. "\n";
}
return $table_error;
}
}
top();
echo "<form name=\"Form\" action=\"mono.php\" method=\"post\">\n";
echo "Enter text you want to encode or decode:<br>\n";
echo "<font size=-1>[- note: lowercase characters and no space -]</font><br>\n";
echo "<textarea name=\"plain\" cols=40 rows=7 class=\"txtcolor\">\n";
if ($plain){
$plain=filter($plain);
$plain=check_length($plain);
echo $plain;
}
echo "</textarea><br><br>\n";
echo "<table border=1 cellspacing=0 bordercolor=\"#000000\">\n";
echo "<th colspan=13>Substitution Table :</th>\n";
echo "<tr>\n";
for($i=0;$i<=12;$i++){
echo "<td align=center>".ascii_letter($i)."</td>\n";
}
echo "</tr><tr>\n";
for($i=0;$i<=12;$i++){
echo "<td>\n";
echo "<select name=\"key[$i]\" width=200 class=\"txtcolor\">\n";
echo "<option>--</option>\n";
for($j=0;$j<=25;$j++){
echo "<option value=".ascii_letter($j).">".ascii_letter($j)."</option>\n";
}
if (ascii_letter($j)==$key[$i]){
echo "<option value=".$key[$i]." selected>".$key[$i]."</option>\n";
}
echo "</select>\n";
echo "</td>\n";
}
echo "</tr><tr>\n";
for($i=13;$i<=25;$i++){
echo "<td align=center>".ascii_letter($i)."</td>\n";
}
echo "</tr><tr>\n";
for($i=13;$i<=25;$i++){
echo "<td>\n";
echo "<select name=\"key[$i]\" width=200 class=\"txtcolor\">\n";
echo "<option>--</option>\n";
for($j=0;$j<=25;$j++){
echo "<option value=".ascii_letter($j).">".ascii_letter($j)."</option>\n";
}
if (ascii_letter($j)==$key[$i]){
echo "<option value=".$key[$i]." selected>".$key[$i]."</option>\n";
}
echo "</select>\n";
echo "</td>\n";
}
echo "</tr>\n";
echo "</table>\n";
echo "<br><br>";
echo "<input type=\"submit\" name=\"process\" value=\"Encode/Decode\" class=\"txtcolor\">\n";
echo "</form>\n";
if ($process=="Encode/Decode"){
$key_table="";
for($i=0;$i<=25;$i++){
$key_table=$key_table.$key[$i];
}
$cipher=mono($plain,$key_table);
echo "Text after encoding or decoding:<br>\n";
echo "<textarea cols=40 rows=7 class=\"txtcolor\">$cipher</textarea><br><br>\n";
}
bottom();
?>
