Day 3ish: Bit Twiddling & Raft

Alas, this post is late—I left my computer at Hacker School last night and thus couldn't post until I got back this morning. But I'm talking about what I did during Day 3 so this still counts as blogging every day, right?

Anyway! I got some real headway in the crypto challenges, which was satisfying, though, as one might expect, it turns out twiddling bits in Python is rather annoying compared to something like C. Python tries very, very hard not to let you operate on raw bits, so you end up doing a lot of awkward conversions. Like, for the task of "this hex string has been XOR'd against a single character; figure out what character that is," I would up with some code that looked like this...

[chr(ord(byte) ^ key) for byte in hex_str.decode("hex")]

...which is (1) decoding the hex string, (2) reading that one byte at a time, (3) XOR'ing the value of the byte against the key, and (4) converting that back to a character representation. I wound up fumbling a bit getting those conversions nested correctly... I'm hoping to think of a more "systematic" way of handling these soon, maybe like a unicode sandwich for bit-twiddling. Or I could just convert everything to bitarrays and handle the problems that way; we'll see.

I also spent the afternoon reacquainting myself with my faltering early attempt at implementing Raft in Python, which was last updated, uh, seven months ago. I hadn't realized I'd left it abandoned for so long! Definitely hoping to wrap that project up (or maybe just start over from scratch) before I leave New York...

Day 4: Presentations and such!

Crypto challenge update: I can now decrypt repeating-key XOR and detect ECB encryption, woohoo! Now that I'm done with the first "set" of challenges, though, I think I'll take a bit of a break—they're super fun, and I'll come back to them later, but I want to start pairing more and explore some other things, too.

Tonight there was a round of presentations from other Hacker Schoolers and goodness they were awesome. Highlights included: Allison poking around to see how the recursion limit is implemented in Python and discovering amusing details therein, Eunsong's Javascript-based molecular dynamics simulator, and Tanoy demonstrating both his live coding skills and his excellent taste in music by making a Jekyll blog and dropping it on Digital Ocean in less than the amount of time it takes to listen to one rap song.

To wind down this evening, I wanted to dust off my old Heroku account and deploy a Flask app there (I've been trying to move some things off my Linode, and this seemed like an easy one to handle), and ran into a bunch of annoyances with key management. The first key I tried to give Heroku was rejected because "that's already being used by another Heroku account," which suggests I've got yet another account on the internet I've forgotten about, oops. The second key I used authenticated fine, but I couldn't push to git—since my git is configured with a different key—so I had to edit a file in .ssh/config, but the change didn't seem to be helping, and eventually I figured out that I had both an id_rsa and an id_dsa key, and I was referencing the wrong one. Sigh, key management. Hopefully I won't forget about the existence of this Heroku account too, heh.