28 December 2009

Now with twice as many 0's and 1's

New York Times, Code That Protects Most Cellphone Calls Is Divulged:

The GSM algorithm, technically known as the A5/1 privacy algorithm, is a binary code — which is made exclusively of 0's and 1's — that has kept digital phone conversations private since the GSM standard was adopted in 1988.

But the A5/1 algorithm is a 64-bit binary code, the modern standard at the time it was developed, but simpler than the 128-bit codes used today to encrypt calls on third-generation networks. The new codes have twice as many 0's and 1's.

That last statement, while technically true, is remarkably vacuous—even when compared to other sentences in the same article. To an uninitiated reader it gives no hint as to the relative complexity of the two codes (a 128-bit code being 18 billion billion times harder to guess in the absence of any other vulnerabilities).

21 December 2009


For as long as I've been alive, 2010 has been synonymous with "way in the future." It is a little jarring to realize that it is only two weeks away.

As a kid, one of my favorite movies was Back to the Future II, where Marty McFly traveled in time to the year 2015. That doesn't seem all that far away anymore either. Where are our hoverboards?

09 December 2009

The power of incentives (in the wireless industry)

As someone who took a couple of economics classes (and knows just enough to be dangerous), I find AT&T's continued network troubles to be quite puzzling.

[AT&T] has been criticized by owners of the [iPhone] for delayed text and voice messages, sluggish download speeds and other network problems.

[President and CEO for AT&T Mobility and Consumer Markets Ralph] de la Vega cited the heaviest data users, saying that 40 percent of AT&T’s data traffic came from just 3 percent of its smartphone customers.

But he emphasized that the company would first focus on educating consumers about their data consumption in the hope that doing so would encourage them to cut back, even though they are paying for unlimited data use.

(New York Times, "AT&T to Urge Customers to Use Less Wireless Data")

I laughed out loud when I read the headline. AT&T thinks that educating users will get them to consume less data, even if it gives them no incentive to do so. I think this is about as likely to work as encouraging people to emit less carbon while giving them no incentive to do so. The article does say AT&T might be considering a non-constant pricing plan; I hope they realize this is a really good idea, soon.

The unlimited data plan is untenable with today's technology. When you, as a user, actually try and take advantage of your "unlimited" data plan, not only are you limited by the mediocrity of the network, you are making other users very, very sad by congesting the network! Offering unlimited plans only makes sense when you have actually built out sufficient capacity to cover the demand. That's why unlimited long distance calls (on both landlines and cell phones) are a good idea (now), and unlimited data plans aren't.

Carriers and consumers claim to prefer unlimited data plans because they're simple. But that simplicity comes at a huge cost to quality, which I bet many people would be willing to pay some amount to avoid.

Personally, I would welcome pay-per-byte pricing to the wireless industry (though I'm not holding my breath). By making people pay an amount commensurate with their impact on other users, it would avert the tragedy of the commons that is AT&T's network today.

Perhaps more importantly, pay-per-byte also provides the right incentives on the network provider's end. When you pay by the byte, your provider has an incentive to build out capacity, because they want to deliver those bytes to you as fast as possible, so they can free up their resources, so they can push you more bytes, which makes them even more money. Under an unlimited pricing structure, the provider has every incentive to drag their feet. Building out capacity costs them money now, but doing nothing at all doesn't cost them anything until your contract expires.

07 December 2009

The story of Sage

William Stein has written a personal account of how he ended up writing Sage (the free software computer algebra system).

For many years, Stein worked on various bits and pieces of mathematical software to satisfy his own research needs. But with just him and a couple of other people working on it, they kept very low expectations for what would eventually become Sage. After all, how could a small group of people match the work of the thousands of engineers and mathematicians who were hired by the proprietary math software companies?

Stein only decided that Sage had to succeed when his license for Magma was terminated, and he realized (1) how insane it was to be dependent on proprietary secrets for math research and (2) how much leverage proprietary software makers had over him and his career:

Isn't it weird that mathematics can be done that way? In 2004, almost everybody in the world doing serious computations with elliptic curves, modular forms, etc., were using Magma. Magma was the industry standard, Magma had won for the forseable future. David Kohel and I were a big reason why. And yet what kind of mathematics is it, when much of my work fundamentally depends on a bunch of secret algorithms? That's just insane. [...]

Anyway, John Cannon's email [...] seriously scared me. I wasn't in any way confident that Sage would ever replace Magma for my work and teaching, and I had big plans involving interactive mathematical web pages. These plans were temporarily on hold as I was drawn into Sage. But there were still there. What John did with that email is tell me, in no uncertain terms, that if I was going to create those interactive mathematical web pages, they couldn't depend on Magma. "This is to formally advise you that your permission to run a general-purpose calculator based on Magma ends." I was scared. It was also the first time I saw just how much power John Cannon had over my life and over my dreams. That email was sent on a whim. I hadn't got any official permission to run that Magma calculator for a specific amount of time (just open ended permission). What John made crystal clear to me was that he could destroy my entire longterm plans on a whim. I looked around for other options, and there just weren't any. Sage had to succeed. But still I was certain that it just wasn't humanly possible, given that I had to do almost all the work, with limited funding and time.