I am a bit confused about how reCAPTCHA works. I have implemented it
using ROR.
Sometimes even if i specify only one word out of two, it returns true
while sometimes it fails.
I am really confused and not able to understand the behaviour of
reCAPTCHA.
Only one of the recaptcha words is "known" by the system - it is relying on the user performing the captcha to tell the system what the other word is, because it is not machine-readable.
That is the "point" of recaptcha, or the added benefit - it is not only performing a human test, it is also massively group-sourcing translation where automated OCR has failed.
Recaptcha shows two words. One that a computer scanner has scanned and recognized and one that the computer scanner cannot recognize. Recaptcha checks for the word it knows the answer to and saves the response for the unknown word. These responses to the unknown words are compiled and analyzed so that it is essentially "solved" by humans and not by the computer scanner.
Here's more info, in their own words:
"But if a computer can't read such a CAPTCHA, how does the system know the correct answer to the puzzle? Here's how: Each new word that cannot be read correctly by OCR is given to a user in conjunction with another word for which the answer is already known. The user is then asked to read both words. If they solve the one for which the answer is known, the system assumes their answer is correct for the new one. The system then gives the new image to a number of other people to determine, with higher confidence, whether the original answer was correct."
source - http://www.google.com/recaptcha/learnmore
Recaptcha uses two words, one of which is known and one which is unknown (the unknown word is the one that the program is trying to help decipher--it's probably scanned out of an old book or something somewhere!). So really, all the service is looking for is the right answer to the KNOWN word. If that's the word you put it, it will succeed even if you don't put in anything for the unknown word. If you put in the other word (the unknown one) it will fail.
I think that's the main point of recaptcha. It helps developers make difference between humans and robots and it also helps digitalize books.
There're always two words. One is easier to read. If you can read this word, it's fine, you're human.
The second word is a scan from a book where automatic OCR (recognition) is not sure about this word. So users are helping read this word so books can be digitalized better.
Related
I am trying to find an easier CAPTCHA to use with my website. I currently have reCAPTCHA but the users are struggling to get the words right the first time.
I have came across Confident CAPTCHA (here) and would like to know what you guys think about it.
Has anyone used it before?
How safe is it?
Are there similar CAPTCHA's, excluding reCAPTCHA?
Interesting captcha, I have not seen this one before.
I will try to address your second question about How safe is it?. There are no docs available or sample code to check so the analysis is based on using it a few times.
It seems like it should be reasonably secure. I see that it uses a 3rd party service, so you will rely on API calls to generate the HTML markup and validate the captcha.
In their demo, you are required to choose 4 images out of a total of 9 which means the probability of guessing the correct value is about 0.000330688% (1/9 * 1/8 * 1/7 * 1/6).
It essentially works by creating an alpha captcha code based on the sequence of images you choose. So the server generates a random challenge (cat, vehicle, drink, house) and associates each element with a random letter from the range [A-Z].
Clicking the sequence of images creates a captcha code based on the letter assigned to each image (e.g. PKIR) if cat = P, vehicle = K, drink = I, house = R that gets placed in a hidden input and submitted with the form.
Therefore the only way to pass the captcha is to come up with a code that agrees with the sequence of images on the server side.
I would conclude it is relatively secure in that there is no way to defeat the captcha solely on the client side (see this question for example). Since there is no reason for them to ever present anything related to the solution to the client (browser); it would seem logical that the only way to get the correct captcha code is to select the correct images in the correct sequence.
Conclusion:
At first glance, the captcha seems secure (no easy bypasses).
This specific captcha may be more difficult to farm out to human solvers (a positive)
Depending on the number of objects and images in the database, it may be possible to generate a database of words to images.
One potential downfall to the captcha is that certain words may require a moderate level of understanding the English language; non-English speaking users may be completely cut off or at least have to put in additional effort to translate words to their native language.
You may want to do a usability check of this captcha on mobile devices (just a thought).
That's my 2 cents, I hope that helps you out.
I'm using it with ads and well, this is very secure.
About english language, the api support many languages and adapt the questions based on the browser language.
I have used GoogleTranslation to help people who have spoken language out of the ConfidentCaptcha reach.
No problem so far. They are very responsive, a very good support.
About mobile, if you don't use ads, you have a special mobile mode, which make it very easy and adapted to the tiny devices.
I am using recaptcha on my site and it is working fine. Only problem is that just because there are two words, it is getting difficult and time taking process. So I want to show one word of captcha instead of two. The question is can we somehow tell the recaptcha to just show one word, rather then two?
It is urgent so please try to suggest me the solution as soon as possible.
Problem: Once i got recaptcha with language "URDU". So is there any way where i can define that i want recaptcha in english only.
Thanks
Tanu
The whole point of reCaptcha is to have two words - the other word is known, the other must be identified by the user. This is the method reCaptcha uses to decipher unknown words. So no, there is no way to have reCaptcha display only one word as that would defeat its purpose.
Scanned text is subjected to analysis by two different optical character recognition programs; in cases where the programs disagree, the questionable word is converted into a CAPTCHA. The word is displayed along with a control word already known. The system assumes that if the human types the control word correctly, the questionable word is also correct.
I wanted to run some captcha possibities past people to see if they are easily by passed by bots etc.
What if colors were used - eg: there is a string of 10 characters are you ask people to type the red characters of where there are 5? Easy to bypass?
I've noticed a captcha on plentyoffish that involves typing in the characters under the circles. This seems a touch more complex - would this be more challenging for bots?
The other idea I was thinking was putting the requirement in an image as well meaning like in no. 1 above - you can put "type the red characters" in an image and this could change with different colors. Any value here?
Interested in what people think.
cheers
Colours are easy to bypass. A bot just takes the red channel and gets the answer. It is even easier than choosing between many possible solutions. The same applies to any noise that has another colour than the letters the user needs to find.
Symbols that don't touch the letters are very easy to ignore. Why would a bot even look at those circles that probably always stay at the same position? (valid but wasn't asked here)
Identifying circles or other symbols is easier than identifying letters, if one can do the latter, a simple symbol is no challenge.
I think captchas are used too frequently in places where they aren't the best tool. For instance, are you trying to prevent registration spam? Why use a captcha rather than email validation?
What are your intentions and have you considered alternatives to the (relatively ineffective) captcha technology?
As a side note, if you have to use them, I prefer KittyAuth myself :) http://thepcspy.com/kittenauth/#5
Color blind people will have trouble separating red from green letters. People who have trouble reading and understanding descriptions, or have other disabilities may have trouble reading the captchas too.
In some of these, the texts are so mangled that almost everyone has a hard time reading them.
I think captcha's, if used at all, should be quite easy to read. The one with the dots and triangles is doable, although it's a matter of time before someone writes an algorithm to hack them. It is very easy for computers to read this kind too.
The best way to deal with this, is increase moderation. Make your site so that it isn't rewarding to spam it at all. Don't make it the problem of your users.
Also, if you're gonna use captcha's, it may be better to build something yourself than to use common libraries. I've found that these are easier hacked, probably because it is more rewarding to write a captcha solver for something that is used by thhousands of sites.
No matter which CAPTCHA you construct, spammers will find a way to work around it, given enough incentive. Large CAPTCHA services like reCAPTCHA, for instance, get bypassed by outsourcing solving them to cheap labor in India(source).
If you run a small site, your best bet is to make your own mini-CAPTCHA, which asks a simple question. If it isn't a standard question, isn't a standard CAPTCHA module and isn't a large site, it isn't worth it for the spammers to automate bypassing it.
I've been working on a community site for an organization at my university, and we've had trouble with spammers registering, despite us using every CAPTCHA module in the book. As soon as we made our own simple one-question CAPTCHA, all spam stopped. The key to preventing this sort of spam often lies in uniqueness.
This was asked in an interview.
I think the answer can be done by constructing a trie of all valid words and then suggestions can be made based on a possible valid path which was otherwise given as incorrect.
Say if user types apfle, and system would detect that after ap a possible valid path was app, which would then satisfy apple.
Is there any better solution than this? Perhaps the one implemented by spell checkers.
See:
How does the Google "Did you mean?" Algorithm work?
How do I approximate "Did you mean?" without using Google?
How to write a spelling corrector
Youtube Video: Search 101
Within typical search engines you will find a lot of Analyzer stuff, which directs to the same underlying problem. A very popular Analyzer would be the n-gram Analyzer.
Perhaps this helps.
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I am writing a user manual and I have come to a discussion with a colleague. He says I cannot use the word "you" anywhere in the manual. Now I remember something about this at school but that was not for writing procedures. Also, doing some googling I observed that most tutorials where using it a lot. I would prefer using it but only if this is considered good practice. what do you think?
The alternatives that I know of are:
'You' (second person singular) - "You should put the plate on the table."
Imperative - "Put the plate on the table."
'We' (first person plural) - "We should put the plate on the table."
'The user' (third person singular) - "The user should put the plate on the table."
Passive - "The plate should be put on the table."
My own preferences are:
I prefer the imperative as the default mode, because it's the briefest (least verbiage).
I avoid the passive, and the first person plural.
I use the second person pronoun ("you") or a third person noun (e.g. "your system administrator") when I want an explicit subject instead of the imperative.
Some people believe that manuals should be written as if they were scientific papers. Others believe that technical accuracy and readability is more important. I'm of the latter persuasion - use "you" if it fits with your overall style, but be consistent in your usage - I find documents that switches between "you" and "we" are irritating (and it's a sin I've been guilty of myself).
Which is easier to understand?
Click the button. You will see a dialog box where you can type your name.
or
The action of clicking the button will cause the appearance of a dialog box allowing the possibility for the user to enter his or her name.
The first is much easier to grasp. (Using "you" can sometimes be sloppy, but that tends to be in cases where it's used as a substitute for "one", or "some people", or "people in general". It's fine to use it where you are actually referring to the person reading the text.)
If you want, you can avoid the
you-style by writing in the
passive/imperative style. You can
also try the 'we' approach, but that
might sound a bit childish. You're
doing nothing wrong with using you
though.
To avoid writing in the you-style,
use the passive/imperative style. The
we-approach might also work, though
it might sound a bit childish. There
is nothing wrong with using you
though.
We can avoid writing in the you-style
by employing the passive/imperative
style. Or we could use the
we-approach, though we might sound a
bit childish. One could try the one
approach, but risk sounding to
stiff-upper-lip and alienating the
reader. We don't mind using you once
in a while, though.
I myself do prefer the second line. A series of commands is easier to follow then a story in the you-form.
You should be writing explantions in the third person.
The Java streams model is a classic Decorator pattern example.
You should write instructions in the second person, but even then, it's still not a good idea to refer to the reader as "you".
Create a constructor that can initialize lists based on a given list of lists.
Now, how did you feel after I issued 2 commands to you, my reader?
Technical Writing Enforce the rule of using passive text only. which mean avoiding "you" will be a good idea to stay in the safe side. that's based on how i do it personally.
I would do what Google, Microsoft, Yahoo, etc do. Here's a random Help page from Google:
http://mail.google.com/support/bin/answer.py?hl=en&answer=8494
shows that "you" is being used. You can check how Microsoft writes their User Manual too.
As a side note, I wouldn't use "I" or "we".
I think if you are providing imperatives, such as "Open the door", or otherwise directly addressing the reader, then you should use "you" instead of making yourself more difficult to comprehend by talking about some abstract user.
Even in scientific papers, some of the most formal writing I can think of, it is debatable whether or not I, we and other first person language is permissible. As much as high school grammar teachers might like you to think otherwise, there is no universally appropriate scheme.
I would say just be careful. It could come across as too casual. If the intended audience is business-y, I would avoid it. However, if it's a home user scenario or the marketing is casual (think Southwest Airlines), I'd say go with it.
Just don't overuse. Then it becomes taxing on the reader.
Sample of how it's intended to be used?
It all depends on the tone and style of your writing. Formal approaches discourage the use of "you". Personally, I like
to use a style that is concise, to the point and relatively informal. I have no problem with the "you" word when used sparingly.
Avoid over usage as in:
When you want to start the application you have to enter your password and then you have to select the function you want to use.
From the Handbook of Technical Writing. 8th Edition (p. 262):
You can make sentences shorter by leaving out some articles(a, an, the), some pronouns (you, this, these), and some verbs, but such sentences may result in telegraphics style and be harder to understand.
So, I'd say it's OK to use you, but like Gilbert Le Blanc said in his comment, it's often better to write 'then click the button' instead of 'then you click the button'.
Impersonal form should be preferred. The use of 'you' would be too clear, and most of your clients will believe you are not professional. A clear manual will also reduce the need for post-sale customer support, and cause losses to the company.