# Sending encrypted emails

1. Mar 18, 2014

### Jamin2112

I came up with a reversible text encryption scheme and I'm trying to figure out how to make it useful. How do you suggest I do that? Should I make an application that people download onto their machine and use to open emails? For starters, should I just make a (secret) website that has an input cell where a user can paste text and click "Encrypt" or "Decrypt"? That's what I'm doing at the moment.

2. Mar 18, 2014

### Fredrik

Staff Emeritus
There are lots of things wrong with that. A person who sends encrypted emails isn't going to want you to be able to read them. They're not going to want anyone who has intercepted a message to be able to read it.

3. Mar 18, 2014

### Jamin2112

That's why the idea here is that only the 2 people in correspondence have access to the decrypting tool.

4. Mar 18, 2014

### AlephZero

Do some research into what already exists (e.g. PGP) and then invent a better mousetrap, if you can.

5. Mar 19, 2014

### Fredrik

Staff Emeritus
It sounds like at least 3 people will have access to it. The third is the web site administrator, i.e. you. Actually it sounds like everyone who will be using your encryption software will have access to it. Suppose that many people are using the system, and that A wants to send a message to B that only B can read, even if E intercepts it somehow. How does she do that? By your description, it sounds like E will have access to the decryption tool, even if she has so far only been using the system to send secret messages to F.

Last edited: Mar 19, 2014
6. Mar 19, 2014

### Jamin2112

Anyways ......

Open this in your browser to try my encoder and decoder.

Code (Text):

<html>

<title>Simple encrypt/decrypt</title>

<style type="text/css">

body
{
background-color: #A9F5F2;
width: 900px;
}
.outerdiv
{
margin: 5px;
border: 2px solid #FF8000;
background-color: #FFFFFF;
}
.outerdiv > p
{
margin: 5px;
word-wrap:break-word
}
.outerdiv > h1
{
margin: 5px;
}
#col1
{
width: 500x;
height: 800px;
float: left;
}
#col2
{
width: 295px;
height: 1500px;
float: right;
font-family: Courier New;
overflow: hidden;
}
#title1div
{
font-family: Arial;
width: 100%;
}
#insctdiv
{
font-family: Arial;
width: 100%;
}
#iptdiv
{
height: 400px;
width: 100%;
}
#buttonsdiv
{
text-align: center;
width: 100%;
}
#inputText
{
width: 100%;
height: 100%;
resize: none;
}

</style>

<script type="text/javascript">

function encrypt()
{
var text = document.getElementById("inputText").value;
newstring = "";
/* Make newstring a string of the bit representations of
the ASCII values of its thisCharacters in order.
*/
for (var i = 0, j = text.length; i < j; i++)
{
bits = text.charCodeAt(i).toString(2);
newstring += new Array(8-bits.length+1).join('0') + bits;
}
/* Compress newstring by taking each substring of 3, 4, ..., 9
consecutive 1's or 0's and it by the number of such consecutive
thisCharacters followed by the thisCharacter.
EXAMPLES:
"10101000010111" --> "10101401031"
"001100011111111111111" --> "0011319151"
*/
newstring = newstring.replace(/([01])\1{2,8}/g, function($0,$1) { return ($0.length +$1);});
document.getElementById("inputText").value = newstring;
}

function decrypt()
{
var text = document.getElementById("inputText").value;
text.trim();
text = text.replace(/([2-9])([01])/g, function (all, replacementCount, bit)
{
return Array(+replacementCount + 1).join(bit);
}).split(/(.{8})/g).reduce(function (str, byte)
{
return str + String.fromCharCode(parseInt(byte, 2));
}, "");
document.getElementById("inputText").value = text;
}

function changeMatrixText()
{
var newtext = "";
for (var i = 0; i < 2530; i++)
newtext += Math.floor((Math.random()*10)+1) % 2 ? "0" : "1";
document.getElementById("matrixText").innerHTML = newtext;
}

</script>

<body>
<div id="col1">
<div class="outerdiv" id="title1div">
<h1>Reversible text encryption algorithm</h1>
</div>
<div class="outerdiv" id="insctdiv">
<p>Type in or paste text below, then click <b>Encrypt</b> or <b>Decrypt</b></p>
</div>
<div class="outerdiv" id="iptdiv">
<textarea id="inputText" scrolling="yes"></textarea>
</div>
<div class="outerdiv" id="buttonsdiv">
<button onclick="encrypt()"><b>Encrypt</b></button>
<button onclick="decrypt()"><b>Decrypt</b></button>
</div>
</div>
<div class="outerdiv" id="col2">
<p id="matrixText"></p>
</div>
<script type="text/javascript">
setInterval(changeMatrixText, 200);
</script>
</body>

</html>

7. Apr 17, 2014

### gmar

When sorcery like this starts flying around most people should realise they are in way over their head and use a standard library.

http://en.wikipedia.org/wiki/Timing_attack

So you might think, OK I'll just add a random delay. But, if you can miss something as wacky as this, what else are you missing?

8. Apr 18, 2014

### Ben Niehoff

That code is not an encryption scheme at all. It's just a compression scheme. It would be pretty easily decrypted.

You should learn about real encryption schemes as was suggested earlier.