Comments on: Google’s New CAPTCHA: The Only Way Is Up!

By: AlexW

AlexW — Thu, 21 May 2009 22:26:54 +0000

@mark Exactly. If I understand correctly, each image would come to acquire a margin for error *specific* to it, based on the normal distribution of results submitted for it. For instance, a profile shot of a doorway might only allow +-2 degrees of error. Other images might build in larger margins.

But, yeah, an average of 1:36 seems reasonable to me, and once you start using more than one at a time the number of possible combinations becomes huge.

By: Mark

Mark — Thu, 21 May 2009 10:29:34 +0000

If the margin of error is 1 in 36 (as guessed at above) then the odds of fluking all three are 1/36 * 1/36 * 1/36 = 1 in 46656. If you reduce this margin of error then it increases significantly – say 2/360 * 2/360 * 2/360 = 6 in 46656000 = 1 in 7776000.

A lot of people seem to be assuming that the same picture will always be rotated by the same amount, and therefore when you get it correct you can store that value somewhere. I would assume the picture is rotated a random amount each time it is presented, meaning you couldn’t assume the same values, and also if you gave the picture a different file name how would you know which picture was being shown? You could also run filters over the images to change them maybe?

I guess image recognition might advance to the point where a machine can tell what it is (like facial recognition), but couldn’t you just put the same squiggly lines over it that any current CAPTCHA has?

By: omnicity

omnicity — Fri, 15 May 2009 19:02:40 +0000

“You only have to look at the comparatively plodding movements of Honda’s Asimo robot or robot soccer to understand just how taxing a task this can be for a machine.”

I’m sorry, but a physical machine trying to imitate natural motion, as an actual method of locomotion has nothing in common with image processing.
This task would probably not need any understanding of the image: if it is possible to detect horizontal or vertical lines in the image, then that gives a completely dumb algorithm a one in four chance of getting a single image right, and therefore 1 in 64 chance with three images, which is easily enough for a brute force approach.

By: FastLionDesign

FastLionDesign — Thu, 14 May 2009 00:18:42 +0000

I think a website should present the beginning of a joke. Then the websurfer would have to provide the punchline (instead of a captcha).

Spammers are a dour, humorless bunch. They wouldn’t be able to figure it out.

George
http://www.fastliondesign.com

By: AlexW

AlexW — Wed, 13 May 2009 01:17:14 +0000

@michael @smarsh Guys, as this is a research paper, it has no current real world implementation, so you can’t assume it won’t have an accessible audio fallback option.

Now, it won’t be an audio equivalent of this system — I can’t imagine how that would work. But there’s no reason why it should be, is there?

So, I can’t see why we’d be any worse off, and in many ways we should be better off.

By: michael - ohio

michael - ohio — Tue, 12 May 2009 14:59:14 +0000

Smarsh is correct: A CAPTCHA system which does not provide an audio option is not viable for any serious website as it would be inacessible to a significant number of people. Assuming that the details of the visual interaction can be worked out – what would the audio option be for the sight impaired?

By: smarsh

smarsh — Tue, 12 May 2009 02:49:16 +0000

There is soooooo much on this site about accessibility – even a forum. It’s a joke to consider captcha a good thing while touting the need for accessible web sites.

One or the other people – make up your minds!

By: AlexW

AlexW — Tue, 12 May 2009 00:09:20 +0000

If you read the detail of the white paper, the user would be presented with more than one image to re-orient (three most likely). I guess you could think of this like a combination barrel lock. A machine might well fluke one at the right angle, but acing all three would be tough.

This also provides a test bed for images. Some images are going to be less obvious than others — for instance a close-up of table setting versus a person standing in a doorway.

As data accrues the table setting shot might allow for a +-10 degree margin for error. The door shot may only allow 2 degrees. The system would learn.

This means, like spam email filtering, the system will automatically evolve and improve as people use it.

@melissapbr I doubt you would try to produce an audio equivalent of this method. What is the audio equivalent of up? I would think this would be teamed with more traditional accessible fallback options.

By: melissapbr

melissapbr — Mon, 11 May 2009 16:57:42 +0000

what would be the accessible alternative for screen reader users?

By: peach

peach — Mon, 11 May 2009 09:42:00 +0000

if google would use a pool of images like flickr they’re going to have a substantial miss-rate from people who cant take picutres straight. Im pretty sure my mobile phone pictures that I upload are rarely straight,