Friday, November 27, 2009

Mimaggia, cairo tester


I've created a simple pygtk project for testing cairo statements. It includes a sort of terminal where you write statements in a simple language. It features immediate preview of what you write.

Say it's a new format for images.
If you want to test it and see the code, ask me.

Saturday, November 14, 2009

Python and RSA

There are many Python toolkits for crypto, so I hope I've done the best choice (at least for now). This is a simple utility class for managing RSA keys, a sort of wrappera to the m2crypto class.

import M2Crypto
class RSA (object):
def __init__ (self, bits=1024, padding=M2Crypto.RSA.pkcs1_padding, exp=65537):
self.bits = bits
self.padding = padding
self.exp = exp
self.rsa = None

def generate (self):
self.rsa = M2Crypto.RSA.gen_key(
self.bits, self.exp, lambda x: None)

def encrypt (self, s):
c = ""
bytes = self.bits/8-11
for i in range(0, len(s), bytes):
c += self.rsa.public_encrypt (s[i:i+bytes], self.padding)
return c

def sign (self, s, algo="sha1"):
dgst = M2Crypto.EVP.MessageDigest (algo)
dgst.update (s)
return self.rsa.sign (dgst.digest (), algo)

def verify (self, s, sign, algo="sha1"):
dgst = M2Crypto.EVP.MessageDigest (algo)
dgst.update (s)
self.rsa.verify (dgst.digest (), sign, algo)
return False
return True

def decrypt (self, c):
s = ""
bytes = self.bits/8
for i in range(0, len(c), bytes):
s += self.rsa.private_decrypt (c[i:i+bytes], self.padding)
return s
Example usage:

rsa = RSA ()
rsa.generate () # generate key pair
s = "a"*2000 # test data
edata = rsa.encrypt (s)
sign = rsa.sign (s)

ddata = rsa.decrypt (edata)
assert rsa.verify (ddata, sign) == True