The problem with current captchas
I think that people > 50 years have problems to recognize the current captchas. So I thought a different approach instead just make harder to read a bunch of symbols (current captcha direction).
A different approach
So I spend time seeking for a different way to separate humans from machines. And I found something more enjoyneable instead of tryng to recognize wierd letters. The result of this was puzzle captcha.
How it works?
On the left, the original image. Right, the puzzled
1. Load a random image from Flickr.
2. Create a puzzle
3. The user can drag the pieces to solve the puzzle, and when finish, click a button to send the result.
Internal mechanism
Each piece contains a code, the first piece has the code A1, the second piece B2, etc. When the puzzle is randomized, that codes are in a random order. When the user sends the result to the server, it must be in the correct order to pass the challenge.
What are the problems of puzzle captcha?
After a little research, I figure out that maybe this kind of captcha it’s easy to solve for a human, but also for a computer. The other nasty thing is that a 3×3 puzzle can take several time to solve (and that isn’t very cool). Maybe we can try with a 2×2 puzzle, but the possibilities to get the solved puzzle are very high, 1:24 (the factorial of 4 => 4.3.2.1).
How machines can solve this kind of puzzles
Machines can compare the % of similarity betwen the borders of each piece. This technique maybe is not 100% successful, but 1% of success is a serious problem. Just think 30 tries per second in 16 hours, that is 17 280 00 intents.
Possible solutions to this problems
- Leave a gap between each piece (losing part of the image) in order to force to the machine bot to compare between inner pixels instead compare the borders.
- Apply a mask with grain or diagonal lines in order to decrease the % of similarity between pieces.
- Show random shapes and then ask to the user to enter the number of a particular kind (i.e. how many red squares are in the image).
- Punish puzzle errors. The user can refresh the puzzle with a new image, but after X tries, she/he must wait 10 minutes.
Current state of puzzle captcha
For me, this project is archived. If you have some ideas or really think that it can work, please leave a comment or reach me.
I see one simple problem.
say you want to actually sent correct sequence to server to get the picture captcha to work. who is going to stop user from predicting the sequence.
if we keep sequence like
A1,A2,A3,B1,B2,B3,C1,C2,C3
and string going out from client is
say
132213123 who is stoping them to change it to
123123123
hope you got my point.