GSoC: Week Two

I spent more time than I should have hacking away at Gajim to make it allow multiple chat windows per user, only to revert it all back when I realised just how big a task it was. I’ve gone the route of one session per contact; if someone starts a new session, the old one is quietly forgotten about. This is far from ideal, but should be sufficient for now. My philosophy on this project is to get something working as soon as possible, and fill out the details later.

Spent quite a while looking for Python libraries that might implement AES:

• PyAES: dead, replaced by CryptKit
• CryptKit: appears to be dead.
• alo-aes: appears to be dead. no documentation.
• pyopenssl: Gajim already uses this if it’s available, so it would be ideal; unfortunately it doesn’t seem to expose any of OpenSSL’s cipher functions.
• PyCrypto: I went with this because it was the first thing I found that works and has documentation.

I ran across M2Crypto after I’d gotten started; it’s another wrapper for OpenSSL. It might make sense to rewrite the current OpenSSL stuff and use this for everything.

As for interesting things, my branch of Gajim can send and receive encrypted messages - take a look at the screenshot I’ve included. It’s not actually very useful because keys and counters have to be hard-coded, but once I get XEP-0217 up and running (hopefully sometime in week three), that should no longer be an issue.

My lack of cryptographic experience is beginning to show. My mentor (Ian Paterson) has been very helpful in pointing me in the right direction. I’ve also discovered that the Handbook of Applied Cryptography is available online; it’s filling me in on the basics and looks like a good reference.