Mining task instead of captcha - will take off?

Question

CAPTCHA

I did not create a post, because it is too small for a post. I invite you to discuss here.
The bottom line: what happens if, instead of captcha, you protect operations that can be abused with a simple mining problem?
The fundamental difference between a normal user and a spammer (when we protect the writing of messages / registration) or a brute-forcer (when we protect the authorization form) is in the number of requests per unit of time. At the same time, the attacker is not necessarily a bot, and a normal user is a human - it is not difficult to hire a team of Indians to send spam, and a normal user can use an answering machine or IM transport for good purposes.
However, if we demand to brute the hash to confirm the request, the enemy will have to spend a lot of computer time to pollute the forum or hack the account, and neither Indians nor the coolest OCR will help him. At the same time, the user will not be very upset if authorization or sending a post takes a few seconds - roughly, the same few seconds he will look at and type captcha.
As a hash algorithm, let's take Script or another algorithm that is difficult to hardware accelerate. The JS-library will deal with the solution of the problem.
In the case when protection by this method is in the interests of the user, and not the service itself (protecting the authorization of his account, for example) - we will give him the opportunity to choose an algorithm and set the complexity in order to find the optimal point for himself between protection and convenience. Libraries like cryptojs allow you to count many different algorithms, so expanding the "range" is very simple.
What do you think?

Answer 1

Why would it be difficult for Indians to sit for a few seconds instead of typing captcha?