Archive for: October, 2008

Reviewing the TMobile G1 - aka the Google Android Phone

Oct 29 2008 Published by under Chatter

Once again, please don't forget about our DonorsChoose drive! Please click in the panel to you left, and go make a donation to help schools get the supplies they need to be able to teach math!

IMG_0007.JPG

Most people must have heard by now that about a week ago, T-mobile
released the first Android based phone, with software by Google. I've been using an Android as a tester for about 6 weeks, and I'm now allowed to talk about it, so I thought I'd post a review from the viewpoint of an extreme geek. Please excuse the low quality of the images; I took the pictures using my iPhone.

Obviously, there's a bit of a conflict of interest here. Google is very proud of the Android software, and I'm very happy and proud to be a software engineer at Google. I think that my review of the phone is fair
and unbiased, but take that with a grain of salt, given my connections.

So, as I said, I've had the phone for about six weeks now. For a little over a year before I got my Android, I was using one of the original iPhones (not the 3g). So in a lot of things, I'm
going to compare my experiences with the Android to my experiences with the iPhone.

Overall, I love the Android. It's not without its flaws, and some of them are fairly significant. I'll go into details below, but the short summary of my opinion is that the software is excellent, the hardware less so.

To be honest, I think the software is really late-beta quality. It's lacking polish, and there are a few awkward points. But overall, it's
extremely well done. Details below the fold.

Continue Reading »

No responses yet

Margin of Error and Election Polls

Oct 28 2008 Published by under statistics

Before I get to the meat of the post, I want to remind you that our
DonorsChoose drive is ending in just a couple of days! A small number of readers have made extremely generous contributions, which
is very gratifying. (One person has even taken me up on my offer
of letting donors choose topics.) But the number of contributions has been very small. Please, follow the link in my sidebar, go to DonorsChoose, and make a donation. Even a few dollars can make a
big difference. And remember - if you donate one hundred dollars or more, email me a math topic that you'd like me to write about, and I'll
write you a blog article on that topic.

This post repeats a bunch of stuff that I mentioned in one of my basics posts last year on the margin of error. But given some of the awful rubbish I've heard in coverage of the coming election, I thought it was worth discussing a bit.

As the election nears, it seems like every other minute, we
hear predictions of the outcome of the election, based on polling. The
thing is, pretty much every one of those reports is
utter rubbish.

Continue Reading »

No responses yet

How Not to Do Message Integrity, featuring CBC-MAC

Oct 24 2008 Published by under Encryption

In my last cryptography post, I wrote about using message authentication codes
(MACs) as a way of guaranteeing message integrity. To review briefly, most ciphers
are designed to provide message confidentiality - which means that no one but the
sender and the intended receiver can see the plain-text of the message. But
ciphers that provide confidentiality don't necessarily make any guarantees that
the message received is exactly the message that was sent. There are a good number
of cryptographic attacks that work by altering the message in transit, and
depending on the cipher, that can result in a variety of undesirable
results.

For example, if you use DES encryption with the ECB mode of operation,
you can insert new blocks anywhere in a message that you want. By using
a replay attack (where you take encrypted blocks from other messages using
the same encryption, and resend them), an attacker can alter your messages, and
you won't be able to detect it.

So in addition to just confidentiality, we need to provide integrity. What does integrity really mean? Basically, it expands the definition of the
decryption function. Written as a function signature, confidential message
decryption is a function decrypt : ciphertext × key → plaintext. With message integrity, we add the
option that decrypt can return a result saying that the message is invalid: decryptinteg : ciphertext × key → (plaintext | REJECT).

Continue Reading »

One response so far

Credit Default Swaps: Gambling as Insurance

Oct 23 2008 Published by under Bad Economics

So, the financial questions keep coming. I'm avoiding a lot of them, because
(A) they bore me, and (B) I'm really not the right person to ask. I try to stay
out of this stuff unless I have some clue of what I'm talking about. Rest assured, I'm not spending all of my blogging time on this; I've got a post on cryptographic modes of operation in progress, which I hope to have time to finish after work this evening.

But there's one question that keeps coming in, involving the nature of things
like so-called "Credit Default Swaps", which I thought I'd explained, but
apparently my explanation wasn't particularly clear. So I thought I should fill
in that gap, and strengthen the main weakness in my earlier explanations.

The basic question is: "What's a credit default swap?"; I think what people
really want to know is both what, specifically, a credit default swap is, and how
the system surrounding credit default swaps and related monstrosities work.

Credit default swaps are interesting - in the same way that a Rube Goldberg
device is interesting. They are in a fundamental sense very simple, but the
structure that's built up around them is so bizarre, so ridiculous on the face of
it, that when you look at it in retrospect, it's hard to believe that anyone
actually thought that it was a good idea, or that it could ever work.

Continue Reading »

30 responses so far

Stupid Economic Comparisons at the New York Times

Oct 14 2008 Published by under Bad Economics

nyt-stocks.png

This is just a short gripe at the NYT, and a feature
that they included in today's Op-Ed section.

It purports to compare how the economy does under democratic versus
republican administrations. They claim that they're computing the returns
on a 10,000 dollar stock investment under 40 years of republican
administrations and 40 years of democratic administrations, in the 80 years
since 1929.

Continue Reading »

35 responses so far

Infinity is NOT a number

Oct 13 2008 Published by under Uncategorized

Writing this blog, I get lots of email. One of the things that I get over and over again is a particular kind of cluelessness about the idea of infinity. I get the same basic kind of stupid flames in a lot of different forms: arguments about Cantor's diagonalization; arguments about
calculus (which I've never even written about!); arguments about
surreal numbers; and worst of all, arguments about nullity.

Continue Reading »

115 responses so far

Friday Recipe: Stuffed Flank Steak

Oct 10 2008 Published by under Recipes

This is a recipe I created just a couple of weeks ago. I saw a beautiful Angus beef flank steak on sale, and wanted to find something to do with it. I came up with this idea of stuffing it. Amusingly, the day after it, a recipe appeared in the New York Times food section for a stuffed flank steak. But there's really nothing common between the two except the name.

The basic idea behind this is that flank steak has a terrific flavor, but it can be a bit tough. So I wanted to do something to it that would
make it tender, while taking advantage of that terrific flavor. The idea I came up with was to flatten it out by butterflying and pounding with a tenderizer, and to marinate it with some wine. After doing that, I had a very large, very thin piece of steak. So I wanted to roll it up - and if you're rolling, you've got a great chance to put something between the layers of the roll. I used a bit of bacon in the recipe - it's important not to give in to temptation and use more. Bacon has a very strong flavor, and you want to complement the flavor of the flank steak, not overwhelm it.

Continue Reading »

No responses yet

Nobel Prize Blogging: Symmetry Breaking

Oct 07 2008 Published by under goodmath

Today the 2008 Nobel Prize winners were announced for physics. It was given to three physicists who described something called symmetry breaking. Since most people don't know what symmetry breaking is, but people remember me writing about group theory and symmetry, I've been getting questions about what it means.

I don't pretend to completely understand it; or even to mostly understand it. But I mostly understand the very basic idea behind it, and I'll try to pass that understanding on to you.

Continue Reading »

No responses yet

Cryptographic Integrity using Message Authentication Codes

Oct 06 2008 Published by under Cryptography

I don't have a lot of time to write; I'm having my fifth (I think) upper endoscopy done tomorrow, which means that the day's going to be a wash; and Yom Kippur is thursday, and I need to cook, so between the personal crap and work, I'm not going to have much time for blogging. So I'm trying to make use of the time I have to write one short but (hopefully) interesting post.

One thing that I've mentioned in passing is the distinction between message confidentiality, and message integrity.

Confidentiality is most of what we've been talking about
so far. Confidentially provides a guarantee that when you send an encrypted message, no one but your intended recipient is able
to read the plaintext.

Integrity is something very different. Integrity guarantees
that if you send an encrypted message, there's no way that the encrypted message could have been tampered with after you encrypted it, without the recipient knowing it.

Continue Reading »

15 responses so far

Friday Random Ten, October 3

Oct 03 2008 Published by under Music

Don't forget to go and donate some money to schools through
our DonorsChoose challenge. Seriously - throw them a couple of bucks. It doesn't need to be much. There are around three thousand people per day who read this blog; if you each contribute $5, it would more than pay to fully fund every project I chose for the challenge!

And don't forget: if you donate more than $100, you get to pick a topic for a post! (Just email me to let me know you donated that much, and tell me what you want your post to be about.)

  1. Metaphor, "The Sparrow": An excellent track
    from a great neo-progressive band. They've got a very distinctive sound, and this is an excellent example of it.
  2. Marillion, "A Collection": a track off Marillion's
    worst-ever album. It's not a bad song; probably the best
    on that profoundly mediocre album. But that's not saying much.
  3. Sonic Youth, "Fauxhemians": very good, very strange, very noisy stuff.
  4. Porcupine Tree, "The Creator Has a Mastertape": I love Porcupine Tree. This is an excellent track, very typical of them. Great stuff built around highly distorted vocals and guitar, backed by great bass work. Amazingly great stuff.
  5. A Silver Mount Zion, "Sow Some Lonesome Corners So Many Flowers Bloom": Post-rock from a subset of Godspeed You! Block Emperor. They're nowhere close to as good as the full-blown
    Godspeed collective, but they're pretty good. This is off of my favorite Mt. Zion recording, "This is Our Punk Rock, THee Rusted Satellites Gather + Sing". It's very good, with a nice minimalist structure of building up layers.
  6. Peter Schickele, "Allegro Ma Non Troposphere": If you don't know about PDQ Bach, you're sadly deprived. PDQ is the invention of Professor Peter Schickele; he is allegedly the 13th illegitimate grandson of J. S. Bach; the last and least of the
    musical descendants of Bach. Schickele writes music allegedly by PDQ. It's amazingly funny stuff, ranging from slapstick (this
    one starts off with the musicians playing off of the wrong sheetmusic), to the very deep (musical tricks making fun of the typical gimmicks used by various composers; for example, this
    one contains a climbing melody in the beginning that's similar to something commonly used by Vivaldi; but instead of rising up twice or three times the way Vivaldi would, it does it something like twelve times. It's also got a few digs at Mozart, John McLachlan, and a few others.) I happen to have been lucky enough to be in the audience of the performance this recording was made from.)
  7. Zoe Keating, "Legions": This is brilliant and strange. It's a classically trained cellist who performs solo with tape-loop. She starts by laying a basic loop, and then building layers on top of it, until she's got a texture, and then playing the main composition on top of the loop. It's amazing.
  8. Anekdoten, "The Great Unknown": a neo-progressive group that sounds a lot like "Red"-era King Crimson. They're very good, but they sound a bit too much like KC. In general, I think that there aren't enough groups that try to follow in the footsteps of Fripp and Friends, but I'd like to hear something a bit more original. If you listen to one track by Anekdoten, it sounds fantastic. But by the time you've listened to an entire album, you're very bored; it's all so derivative.
  9. The Redneck Manifesto, "Good With Tempos": a post-rock band that's very much in the style of Mogwai, but with their own distinctive style. The Rednecks are fantastic.
  10. Magma, "Ork Alarm": I've mentioned Magma before. They're one of the strangest groups I listen to. They're sort of a cross between classical music and progressive rock. The leader of the band actually invented his own language to sing in, and the singing is more in the style of a choir singing in a symphony. This sounds a lot like a 20th century classical opera. Fortunately, I like
    20th century opera. I'm not a fan of the older, traditional Italian opera like Verdi, but a lot of the 20th century stuff by folks like John Adams, Phillip Glass, and Igor Stravisky have, while not necessarily being traditional opera, been utterly brilliant.

No responses yet

Older posts »