RSA with PyCrypto

[A.M. Kuchling]

On 11 Dec 2002 18:53:36 +0100, 
> # Give B's public key to A... I think...
> privkeyA.e = pubkeyB.e
> privkeyA.n = pubkeyB.n

Don't do this.  

Think of an RSA key as a mailbox.  Any passer-by can drop messages
into the mailbox through the little slot, but passers-by can't get a
message back once it's been placed inside the mailbox; the slot is too
small for them to reach in.  The mailbox owner has a key that permits 
opening up the mailbox and taking out all of the messages.  

RSA keys are like this.  Given the public key, anyone can take a
message and encrypt it using the key.  Only the person who has the
private key can reverse this encryption to get the original message.

So, in your example, A doesn't need an RSA key at all.  A simply needs
to get a copy of B's public key, does 'msgc = pubkeyB.encrypt(msg,"")'
and sends msgc to B.  B then does 'msgd = privkeyB.decrypt(msgc)' 
to retrieve the original message.

--amk                                                             (www.amk.ca)
It's more serious than death, Mr Stevenson. He's changing form.
      -- The Doctor, in "The Seeds of Doom"