Chess CAPTCHA • Hacker News Board

Re: Chess CAPTCHA

#51

Post by bartl » Sun, Mar 10, 2013, 2:55 PM UTC

raverbashing wrote: post #40

bdg wrote: post #21

Can brute force answer from the server quicky: http://en.lichess.org/captcha/0nbdeigw?solution=a1+a2 returns either 1 or 0. The total complexity of this to brute force is 768 possible moves. Most of us here could write a bot to spam their site with less than 30 minutes of time and effort.

Blocking bruteforce is 'easy', just make any attempts after X attempts be void for the given board/ip For the humans, just give another board (and add a time delay)

It's chess. You don't have to use this board to check every possible move, as any engine that knows the chess rules can verify if the result is indeed checkmate, without using this site's engine.

But, basically you're right. If the bot is not using an external chess engine, it could effectively be blocked from brute force attacks the way you describe.

Re: Chess CAPTCHA

#52

Post by rweba » Sun, Mar 10, 2013, 2:56 PM UTC

As I expected most of the HN comments are criticizing it for one reason or another but I like this just because solving simple chess puzzles is FUN which is not true for the tasks in the typical CAPTCHA.

Yes, there could be a concern over a spammer automating the process but that might be more hassle than it's worth just to spam an small chess forum.

Re: Chess CAPTCHA

#53

Post by throwawayG9 » Sun, Mar 10, 2013, 2:57 PM UTC

Swizec wrote: post #45

I am fairly certain it would be quicker to program a computer that can brute force a checkmate in one than I can solve these things by hand. You have what, 11 pieces, they can move into 64 positions each (at most, much less in reality). That means a computer must brute force 64*11 = 704 attempts. In other words, no time at all to bruteforce this once you've read the grid. Reading the grid in itself is rather trivial…

If you don't want to think about how to checkmate maybe this website isn't for you.

Re: Chess CAPTCHA

#54

Post by motters » Sun, Mar 10, 2013, 2:57 PM UTC

Chess doesn't seem like a useful CAPTCHA. To begin with not everyone knows the rules of chess, and secondly computers are much better and much faster than the average human chess player.

Re: Chess CAPTCHA

#55

Post by niggler » Sun, Mar 10, 2013, 2:59 PM UTC

edw519 wrote: post #43

Brilliant building of software. Less than brilliant copy. I would change Black plays; checkmate in one! This is a chess CAPTCHA. Click on the board to make your move, and prove you are human. to This is a chess CAPTCHA... To prove that you are human, click on a black piece, then click on the only destination square that will checkmate. I really don't mean to nitpick, but took me a minute to figure out what to do. Som…

The original copy is better than your proposal: you get to the checkmate point, which is the essence of the captcha, at the very end.

The way it was originally laid out, it's clear that you are looking for checkmate in one, while in your copy it seems acceptable to click any black piece.

Re: Chess CAPTCHA

#56

Post by Swizec » Sun, Mar 10, 2013, 2:59 PM UTC

throwawayG9 wrote: post #53

Swizec wrote: post #45

I am fairly certain it would be quicker to program a computer that can brute force a checkmate in one than I can solve these things by hand. You have what, 11 pieces, they can move into 64 positions each (at most, much less in reality). That means a computer must brute force 64*11 = 704 attempts. In other words, no time at all to bruteforce this once you've read the grid. Reading the grid in itself is rather trivial…

If you don't want to think about how to checkmate maybe this website isn't for you.

Probably not, but we are talking about the CAPTCHA itself :)

You raise a good point about making captchas that target your target audience in that they aren't really designed to keep out bots, but humans who wouldn't fit in. This looks very much like that sort of captcha.

Re: Chess CAPTCHA

#57

Post by tjoff » Sun, Mar 10, 2013, 2:59 PM UTC

bdg wrote: post #21

Can brute force answer from the server quicky: http://en.lichess.org/captcha/0nbdeigw?solution=a1+a2 returns either 1 or 0. The total complexity of this to brute force is 768 possible moves. Most of us here could write a bot to spam their site with less than 30 minutes of time and effort.

You would do an online bruteforce? I think hundreds of moves in a few seconds kind of rule out a human...

Just implement your own check-mate check if going the brute-force route.

Re: Chess CAPTCHA

#58

Post by mistercow » Sun, Mar 10, 2013, 3:01 PM UTC

This will be effective as long as it isn't widespread, but there are much simpler CAPTCHAs you can use to avoid spam if you want to take the obscurity approach. For example, I've had great success with simple traps that just make it hard for automated programs to figure out the input form. That approach is completely invisible to human users.

But if you do go for obscurity, you're going to lose once your technique becomes widespread, or once your site becomes big enough to be worth targeting.

Re: Chess CAPTCHA

#59

Post by bambax » Sun, Mar 10, 2013, 3:11 PM UTC

ornicar wrote: post #44

edw519 wrote: post #43

Brilliant building of software. Less than brilliant copy. I would change Black plays; checkmate in one! This is a chess CAPTCHA. Click on the board to make your move, and prove you are human. to This is a chess CAPTCHA... To prove that you are human, click on a black piece, then click on the only destination square that will checkmate. I really don't mean to nitpick, but took me a minute to figure out what to do. Som…

thanks for the feedback, I will apply the suggested change soon.

Please don't! The original is better and gets the point accross faster than the suggested change.

Re: Chess CAPTCHA

#60

Post by mich41 » Sun, Mar 10, 2013, 3:16 PM UTC

edw519 wrote: post #43

Brilliant building of software. Less than brilliant copy. I would change Black plays; checkmate in one! This is a chess CAPTCHA. Click on the board to make your move, and prove you are human. to This is a chess CAPTCHA... To prove that you are human, click on a black piece, then click on the only destination square that will checkmate. I really don't mean to nitpick, but took me a minute to figure out what to do. Som…

Black plays; checkmate in one!

What can be more clear than this?

If anything, I'd prefer to have the king I'm supposed to checkmate standing on a red field to make it easier to spot.