pycrypto 3DES keysize

[hg]

Ning wrote:

> I'm trying to write an IM client which sends encrypted messages to the
> server.  I tried to use pycrypto library, but when I came to 3DES
> cypher I was confused about the keysize to use.  In the standard it
> said that it should be either 112 bits or 168 bits, whereas it's 16
> bytes or 24 bytes in pycrypto.  If I use 16 bytes key to encrypt and
> send this key to the server which is expecting a 112 bits key, there'll
> be a problem.  How I should solve this?

You need to account for the parity bits:
http://en.wikipedia.org/wiki/Triple_DES


If that may reassure you ;-) I use PyCrypto to "talk" to smart cards without
any problem.

hg