Roberto Martínez: RSA-based digital signature

martes, 18 de septiembre de 2012

RSA-based digital signature

For this homework I need to implement a HTTP public-key repository for key exchange that employs RSA-Based digital signatures, so for make this assignment I used PHP and a little database in mysql also a little script in Python.

First of all, this is my code:

This is the PHP+MySQL code

	<?php
	$conectar = mysql_connect("***", "**", "****") or die(mysql_error());
	$select = mysql_select_db("*******", $conectar);

	function f($x){
	return ($x * $x);
	}

	function fastmodexp($x, $y, $mod){
	$p = 1;
	$aux = $x;
	while($y > 0){
	if ($y % 2 == 1){
	$p = ($p * $aux) % $mod;
	}
	$aux = ($aux * $aux) % $mod;
	$y = $y >> 1;
	}
	return ($p);
	}
	?>

	<html>
	<head>
	<title>Web Service - RSA-Based digital signatures</title>
	</head>
	<body>
	<a href="http://robertomtz.comeze.com/script.py">Download script</a></br>

	<?php
	if(isset($_POST['Generate'])){
	$random = rand(0, 9);
	}

	if(isset($_POST['Check'])){
	$usuario = $_POST['usuarios'];
	$x = $_POST['challengen'];
	$r = $_POST['response'];

	$E = mysql_fetch_row(mysql_query("SELECT E From Usuarios WHERE Usuario = \"". $usuario . "\""));
	$N = mysql_fetch_row(mysql_query("SELECT N From Usuarios WHERE Usuario = \"". $usuario . "\""));

	$e = $E[0];
	$n = $N[0];

	$y = f($x);
	$num = fastmodexp($r, $e, $n);

	if ($y == $num){
	echo "<strong><h2>Yes, it was ". $usuario ." :)</h2></strong>";
	} else {
	echo "<strong><h2>No, it wasn't ". $usuario ." :(</h2></strong>";
	}
	}
	?>

	<form action = "<?php echo $_SERVER['PHP_SELF']; ?>" method="post">
	Challenge: <?php echo $random; ?>
	<input type="submit" name="Generate" value="Generate" />
	</form>

	<form action = "<?php echo $_SERVER['PHP_SELF'];?>" method="post">
	<input type="hidden" value="<?php echo $random; ?>" name="challengen"/>
	<?php
	$strmysql = "SELECT Usuario FROM Usuarios";
	$usuarios = mysql_query($strmysql);
	$select = "<select name=\"usuarios\">";
	while($fila = mysql_fetch_array($usuarios)){
	$select .= "<option value='".$fila['Usuario']."'>".$fila['Usuario']."</option>";
	}
	$select .= "</select>";
	?>

	User: <?php echo $select; ?> </br></br>

	Response: <input type="text" name="response" size = "10" /> </br>

	<input type="submit" name="Check" value="Check" /> </br>
	</form>

	</body>
	</html>

view raw cripto.php hosted with ❤ by GitHub

This is the Python script.

	#!/usr/bin/python
	def f(x):
	return x*x

	def fastmodexp(x, y, mod):
	p = 1
	aux = x
	while y > 0:
	if y % 2 == 1:
	p = (p * aux) % mod
	aux = (aux * aux) % mod
	y = y >> 1
	return p

	def main():
	x = int(raw_input("Escribe tu x -> "))
	d = int(raw_input("Escribe tu d -> "))
	n = int(raw_input("Escribe tu n -> "))
	y = f(x)
	r = fastmodexp(y, d, n)
	print "Esta es tu r = " + str(r)

	main()

view raw script.py hosted with ❤ by GitHub

This is the MySQL database.

	CREATE TABLE 'Usuarios' (
	'Usuario' char(10) COLLATE latin1_general_ci NOT NULL,
	'E' int(10) NOT NULL,
	'N' int(10) NOT NULL
	) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_general_ci;


	INSERT INTO 'Usuarios' VALUES('Alguien', 19, 3763);
	INSERT INTO 'Usuarios' VALUES('Roberto', 67, 253);
	INSERT INTO 'Usuarios' VALUES('Saul', 91459, 9131);
	INSERT INTO 'Usuarios' VALUES('Max', 233273, 73109);
	INSERT INTO 'Usuarios' VALUES('cecy', 59, 5767);

view raw database.sql hosted with ❤ by GitHub

You can access to the application robertomtz.comeze.com/cripto.php

This is useful for example, I am not sure that cecy is the same person that I am chatting on facebook, so Cecy is on my database with a public key and I sent a challenge to Cecy and she download a script that run in local, put her keys and compute a r, she sent me the r and I verify in my web that it was Cecy.

This is an example that I made with Cecy

If I put an incorrect Response:

1 comentario:

Elisa20 de septiembre de 2012, 6:16
No se puede con claves grandes por php :( 9 pts.
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