Everyone knows the annoyance caused by captchas that are unreadable. HashCash is a different kind of validation. Unlike other captcha solutions, HashCash doesn't rely on 3rd party services or resources - and it doesn't require anything from your users other than a JavaScript enabled browser. No mangled words to decipher, no math problems to solve, no photos to match - nothing but arrival on a form page.

Originally proposed by Adam Beck in 1997, HashCash requires a form to include the solution to a complex calculation. The calculation is so complex (it takes hundreds or even thousands of attempts to solve it) that any human or bot attempting to abuse your forms will spend so much processor time solving the calculation that it wouldn't be profitable to continue attacking your forms! The server receives the result and can easily and quickly test it in 1 calculation - either it's right and your user continues or it's wrong and the form submission fails.

The best part is, HashCash is invisible (you can't read it - or even see it) and it happens in the background without user interaction! Your users arrive at the form and the HashCash calculation is automatically executed. Any bot attempting to submit your form without completing the calculation is rejected, and the calculation changes every time the form is submitted.

HashCash is Joomla 5 native. The Joomla compatibility plugin is not required.

Since version 5.1.0, Captcha - HashCash leverages the Web Cryptography API to perform the hashing functions. This puts less stress on the single JavaScript thread, pushing calculation into JavaScript engine itself. Although it makes the calculation run faster, it also doesn't slow your page down or prevent other scripts from functioning properly.

Since 5.2.0, "Delayed Start" is enabled by default. This feature delays the hashing function until the user interacts with the form in some meaningful way (by typing something, choosing a radio/select/checkbox, etc). Bots programmed to wait for the hash value to populate will wait forever. Bots who fill in the form too quickly will not pass the captcha value. I had this idea while eating a cheddar jalapeno sausage at Chili's. It was delicious.

Configuration is simple:
- Choose the difficulty level (default 3)
- The predefined minimum (1) and maximum (5) levels prevent calculations that are too simple or too difficult to complete in an acceptable amount of time.
- Enable Delayed Start (enabled by default)
- This delays the start of calculation until the user interacts with the form