Captcheck
=========
Easy, light, self-hostable CAPTCHA service. Works on all modern browsers and
IE9+. Uses icons from Font-Awesome.
How to use
----------
In your form, put an empty div with the ID "captcheck_container".
Add `captcheck.js` into your page.
Captcheck Sample Form
When the form is submitted, your server will receive two extra form fields:
`captcheck_session_code` and `captcheck_selected_answer`.
In your form handling code, send a request to `http(s)://captcheck-url/api.php`.
Pass the variables `session_id` and `answer_id` with the values sent with the form,
and also pass the variable `action` with the value `verify`.
You will receive a JSON response with (among other things) `"result": true` or
`"result": false`. If result is false, the user failed the test, and another
variable `msg` is available with an explanation.
Example URL:
`http(s)://captcheck-url/api.php?action=verify&session_id=&answer_id=`
Example responses:
`{"session":"some_session_id","result":true}`
`{"session":"some_session_id","result":false,"msg":"Answer incorrect."}`
Execution Flow
--------------
JS = captcheck.js, API = api.php, FORM = parent form,
SITE = form processing code, -> = some action taken on the right by the left
JS -> API: Request session ID, question, and answers (with scrambled random codes)
API -> JS: Sends info, saves session ID, correct answer, and scrambled answer codes in DB
JS -> API: Requests answer images by sending scrambled value and session ID
JS -> FORM: Adds hidden field with value=session ID, displays question and images
[USER SUBMITS FORM]
SITE -> API: Sends session ID and scrambled answer
API -> SITE: Responds with true/false to indicate if the answer is valid, marks session as expired to prevent CAPTCHA reuse