title: RSA encryption and decryption in Python
body: <p>I need help using RSA encryption and decryption in Python. </p>
  
  <p>I am creating a private/public key pair, encrypting a message with keys and writing message to a file. Then I am reading ciphertext from file and decrypting text using key. </p>
  
  <p>I am having trouble with the decryption portion. As you can see in my code below, when I put in <code>decrypted = key.decrypt(message)</code> that the program works, yet the decrypted message is encrypted again. It seems like it is not reading the ciphertext from the file. </p>
  
  <p>Can anyone help me write this code so decryption reads ciphertext from file and then uses key to decrypt ciphertext?</p>
  
  <pre><code>import Crypto
  from Crypto.PublicKey import RSA
  from Crypto import Random
  
  random_generator = Random.new().read
  key = RSA.generate(1024, random_generator) #generate public and private keys
  
  publickey = key.publickey # pub key export for exchange
  
  encrypted = publickey.encrypt('encrypt this message', 32)
  #message to encrypt is in the above line 'encrypt this message'
  
  print 'encrypted message:', encrypted #ciphertext
  
  f = open ('encryption.txt', 'w'w)
  f.write(str(encrypted)) #write ciphertext to file
  f.close()
  
  #decrypted code below
  
  f = open ('encryption.txt', 'r')
  message = f.read()
  
  decrypted = key.decrypt(message)
  
  print 'decrypted', decrypted
  
  f = open ('encryption.txt', 'w')
  f.write(str(message))
  f.write(str(decrypted))
  f.close()
  </code></pre>