Cecilia Urbina: RSA-based digital signatures

Homework:

"Implement a HTTP public-key repository for
key exchange that employs RSA-based digital
signatures."

I used Google App Engine Python for the web service, this is my app http://rsa-ds.appspot.com/.
The script to download and calculate the "r" and "y" is :

	#!/usr/bin/python
	def f(x):
	return x311*7

	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("x: "))
	d = int(raw_input("d: "))
	n = int(raw_input("n: "))
	y = f(x)
	r = fastmodexp(y, d, n)
	print "La r es = " + str(r)

	main()

view raw gistfile1.py hosted with ❤ by GitHub

Google app python:

	import cgi
	import webapp2
	import random
	from google.appengine.api import users
	import datetime
	from google.appengine.ext import db


	def f(x):
	"""devuelve un valor de y
	"""
	return x311*7

	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


	class Usuario(db.Model):
	nombre = db.StringProperty(required=True)
	e = db.StringProperty(required=True)
	n = db.StringProperty(required=True)

	######## users test########

	a = Usuario(nombre="cecy",
	e="59",
	n="5767")
	a.put()
	b = Usuario(nombre="daniel",
	e="13",
	n="2773")
	b.put()
	c = Usuario(nombre="pedro",
	e="23",
	n="3293")
	c.put()
	d = Usuario(nombre="lupita",
	e="89",
	n="3649")
	d.put()
	############################


	class MainPage(webapp2.RequestHandler):
	"""clase principal que muestra el formulario
	"""

	def get(self):
	x = int(random.random()*100)
	self.response.out.write("""
	<html>
	<head> <link type="text/css" rel="stylesheet" href="/bootstrap/css/bootstrap.css" />
	</head>
	<body>
	<div class="container">
	<form class="form-horizontal" action="/generate" method="post">
	<legend>RSA-based digital signatures</legend>
	<div class="control-group">
	<label class="control-label">Challenge</label>
	<div class = "controls">
	<input type="text" name="x" value="%s" readonly="readonly"/>
	<a class="btn" href="http://rsa-ds.appspot.com/"><i class="icon-cog"></i>Generate</a>
	</div></div>
	""" %x)
	usuarios = db.GqlQuery("SELECT * FROM Usuario")
	self.response.out.write("""<div class="control-group">
	<label class="control-label"><i class="icon-user"></i>
	User</label>
	<div class="controls">
	<select name="usuario">""")
	for i in usuarios:
	self.response.out.write("""<option>""")
	self.response.out.write("""%s""" %i.nombre)
	self.response.out.write("""</option>""")
	self.response.out.write("""</select>
	<a class="btn" href="https://docs.google.com/open?id=0BzBiYAUF68vdNFEzMnFIaWhrcjQ">
	<i class="icon-download-alt"></i>Download script</a></div></div>
	<div class="control-group">
	<label class="control-label"><i class="icon-edit"></i>r</label>
	<div class="controls">
	<input class="input-large" type="text" name="r" placeholder="numeric value" size="10" /></div></div>
	<div class="controls">
	<button type="submit" class="btn btn-primary"><i class="icon-check icon-white"></i> Validate</button></div>
	</form>""")
	self.response.out.write("""</div></body>
	</html>""")


	class Calculo(webapp2.RequestHandler):
	def post(self):
	self.response.out.write("""<html><head>
	<link type="text/css" rel="stylesheet" href="/bootstrap/css/bootstrap.css" /></head>
	<body><div class="container">""")
	usuario = self.request.get('usuario')
	r = self.request.get('r')
	x = self.request.get('x')
	y = f(int(x))
	us = db.GqlQuery("""SELECT * FROM Usuario WHERE nombre = '%s'""" %usuario)
	for i in us:
	e = i.e
	n = i.n
	nombre = i.nombre
	try:
	y1 = fastmodexp(int(r), int(e), int(n))
	self.response.out.write("""<div class="row">User: %s</div>
	<div class="row">r: %s</div>
	<div class="row">x: %s</div>""" %(usuario, r, x))
	self.response.out.write("""<div class="row">y = f(x) = %s</div>""" %y)
	self.response.out.write("""<div class="row">Public key: (e,n) =
	(%s, %s)</div>""" %(e, n))
	self.response.out.write("""<div class="row">y1 = r^e mod n = %s</div>""" %y1)
	if y1 == y:
	self.response.out.write('<div class="row"><p class="text-success">Yes, it is correct</p></div>')
	else:
	self.response.out.write('<div class="row"><p class="text-error">Is incorrect</p></div>')
	except ValueError:
	self.response.out.write('<div class="row">r must be a numeric value</div>')
	self.response.out.write('<div class="row"><a href="http://rsa-ds.appspot.com/">Retry</a></div>')
	self.response.out.write('</div></body></html>')

	app = webapp2.WSGIApplication([('/', MainPage),
	('/generate', Calculo)],
	debug=True)