A Picture (or Three) Is Worth A Thousand Words

Iang over at Financial Cryptography talks about the importance of not just which cryptographic algorithm to use, but which mode it is implemented with. He uses three pictures from Mark Pustilnik’s paper “Documenting And Evaluating The Security Guarantees Of Your Apps” that are such a great illustration of the problem, that I have to include them here.
Adam and I have both been to Tufte’s courses on Presenting Data and Information and these strike me as the kind of illustrations he would appreciate. The beauty of them is that as a non-cryptographer, you don’t need to understand the technical differences between ECB and CBC modes, because the illustrations demonstrate them far better than any text could.
[Edit: In the comments, nicko points out this extremely cleaver idea was originally done with the Tux logo from Linux and that they can be found on wikipedia in the section on block cipher modes of operation.]
fig02a.gif
Figure 2a Plaintext
fig02b.gif
Figure 2b ECB Encryption
fig02c.gif
Figure 2c CBC Encryption

Presentations and the Web

bad-presentation.jpgIt’s easy to put presentations on the web, just like it’s easy to create them. Neither is easy to do well. I’d like to talk not only about good slide creation, but how to distribute a presentation in a useful way. It’s not easy to create good presentations, even when you have good content. Simson Garfinkel pointed me to a great source on “The Design of Presentation Slides.” It’s based on actual research about presentation style and retention. It turns out that a full sentence headline, graphical representation of data, and conclusions to draw from the data presented is far more memorable than bulleted sentence fragments (right).

This style also works well when the presentation is actually a presentation of some other organized thinking, such as a scientific paper, or progress report. When the presentation is accompaniment to something, I believe the research that says the headline sentence, data and conclusion style lead to better retention. What about when there is no other handout?

There’s an expectation that speakers at a conference or workshop will provide slides. From the perspective of the conference organizers, requesting slide offers some small assurance that the speaker has prepared, and allows the conference attendees to have the slides as a reminder of the talk. From the reminder perspective, outline slides are actually very useful. There’s rarely an expectation of handouts that aren’t the slides. Perhaps the most useful (generically) is an actual outline, created with a tool designed for that purpose. A real outline is useful because it is less constrained by the genre: ideas can be more than active fragments, and the printed page imposes fewer constraints on both sentence and block than the slide. An outline’s not so useful as data, but who has data these days?

So I think I may move away from my habit of providing multiple formats of the slides themselves, and move to putting up a three-part web page with outline, references, and any details of the argument that seem to require elucidation. Perhaps even a short essay.

I would do this because the two scenarios are so different: One involves having me at the front of a room, using slides to illustrate and orient around my words. The other, without me there, means that the message needs to be self-contained.

Tony Chor on Presenting at MIX

Tony Chor has a good post on “Backstage at MIX06.” The effort that goes into a good presentation, including the practice, the extra machines, the people to keep them in sync, etc, is really impressive:

Normally, when I do a presentation and demo, both the demos and the presentation are on the same machine. I advance the slides and do the demo myself. Sometimes, for a big talk like my keynote at Hack-in-the-Box, we separate out the slides and demo onto separate machines (especially when the demos have pre-release bits like Windows Vista or IE7) and maybe I’ll have someone help me with the demos/slides to keep things running more smoothly.

Well, MIX took that to a whole new level. First, the demo machine was backstage, connected to a monitor, keyboard, and mouse via a switch. We also had a backup demo machine hooked up.