asp.net mvc - reCaptcha valid if first word is correct -

i implementing recaptcha in mvc project follows.

    [httppost]     [validateantiforgerytoken]     [recaptchacontrolmvc.captchavalidatorattribute]     public actionresult index(indextemp indextemp, bool captchavalid)     {         if (!captchavalid)         {             modelstate.addmodelerror("", "you did not type verification word correctly. please try again.");         }          if (modelstate.isvalid)         {             // stuff here         }     } 

and in web.config have following.

<add key="recaptchaprivatekey" value="some_key"/> <add key="recaptchapublickey" value="another_key"/> 

i got recaptcha here.

i noticed recaptcha not work expected (i.e. validates when words entered invalid). after bit of testing noticed long enter first word correctly valid!

any ideas?

this answer helpful: recaptcha authenticates valid 2 incorrect words

from recaptcha wiki:

recaptcha consists of 2 words: verification word, recaptcha server knows answer , read word comes old book. read word not graded (since server using human guesses figure out answer). as such, word can entered incorrectly, , captcha still valid. each read word sent multiple people, incorrect solutions not affect output of recaptcha.

on verification word, recaptcha intentionally allows "off one" error depending on how trust user giving solution. increases user experience without impacting security. recaptcha engineers monitor functionality abuse.