[OSM-talk] ReMAPTCHA Demo BETA 0.2 online! (Was: Hate captchas!!!!)

moltonel 3x Combo moltonel at gmail.com
Mon Mar 31 11:21:06 UTC 2014

On 29/03/2014, Stefan Keller <sfkeller at gmail.com> wrote:
> Hi moltonel
> You wrote:
>> I'm worried about bots still having a very high chance of sucess. With
>> two fairly-legible words in the image and a chalenge asking me to
>> write either one of the words or both, a bot still has 33% chance of
>> success if answering randomly
> I can't follow what 33% means and why you are more worried than about the
> usual CAPTCHAs: The known word (the one which is more scrambled) in our
> ReMAPTCHA currently consists of 5 characters, and the word is placed
> anywhere in the image - slightly tilted. This makes it at least as
> difficult as usual CAPTCHAs.

I'm not an OCR expert, but your scrambling looks less intense than
most CAPTCHAs out there, so I assume that it isn't much of a challenge
for current bots and consider it "solved". From that point onward, the
challenge asks me to look at the map to decide wether to type word A
or words A and B. If a bot can't read the map (that's what we hope),
it'll just try random combinations: either word A, or word B, or words
A and B. That's 33% of success.

Again, you could scramble more heavily or add more words to choose
from. But if you do that, ReMAPTCHA will quickly become as annoying
(if not more) as traditional CAPTCHAs.

The original idea of CAPTCHAs is that humans are better at reading
scrambled characters than computers. But computers got better at that
task, to the point that we have to make the task diffucult for humans
in order to make it difficult from computers.

Today we have a new type of task that humans are supposedly better at:
interpreting satellite imagery. Even better: we're asking the computer
to reproduce a brain process (armchair mapping) rather than a computer
process (reversing the scrambling algorythm).

Please drop the "scrambled text" idea altogether. And make solving a
CAPTCHA a fun activity in the process. A "click features on the
satellite imagery" task is one way to do it, but I'm sure there are

More information about the talk mailing list