Is it similar to https://friendlycaptcha.com/ ?

Author of mCaptcha here o/

Yes, the only differences are that mCaptcha is 100% FOSS and uses variable difficulty factor, which makes it easy to solve Proof-of-Work under normal traffic level but becomes harder as an attack is detected.

It’s funny how they have a section with three human avatars and one robot, with green checkmarks on the humans, yet those faces look AI-generated.

mCaptcha is interesting, but I wonder what its energy impact would be on a sufficiently large deployment, e.g imagine we replaced all reCAPTCHAs with mCaptcha.

Author of mCaptcha here o/

mCaptcha uses PoW and that is energy inefficient, but it not as bad as the PoWs used in blockchains. The PoW difficulty factor in mCaptcha is significantly lower than blockchains, where several miners will have to pool their resources to solve a single challenge. In mCaptcha, it takes anywhere between 200ms to 5s to solve a challenge. Which is probably comparable to the energy used to train AI models used in reCAPTCHA.

The protection mechanisms used to guard access to the internet must be privacy-respecting and idempotent. mCaptcha isn't perfect, and I'm constantly on the lookout for finding better and cleaner ways to solve this problem.

> Which is probably comparable to the energy used to train AI models used in reCAPTCHA

Are you comparing the energy it takes to train a model which is bounded and defined with unbounded inference which can (in principle) go multiple order of magnitude depending on the usage? Or maybe I misunderstood what you are trying to say? then I apologize in advance.

I am, but what I said was more of a hypothesis than a fact :)

From what I understand of reCAPTCHA, the model isn't static and is continuously learning from every interaction[0]:

> reCAPTCHA’s risk-based bot algorithms apply continuous machine learning that factors in every customer and bot interaction to overcome the binary heuristic logic of traditional challenge-based bot detection technologies.

I don't know the energy demands of such a system.

mCaptcha, under attack situations, will at most take 5s of CPU time on a busy (regular multitasking with multiple background process) smartphone.

[0]: https://www.google.com/recaptcha/about/

> Which is probably comparable to the energy used to train AI models used in reCAPTCHA.

I had not considered that. Naturally, we're just speculating here, but yeah that does sound plausible.

I was also no aware of the "hard" 5s bound (which you seem to have tested on a normal smartphone setup); sounds neat.

I expect its not significantly larger than loading your average 2023 webpage with 15MB of js

Doesn't traffic consume more energy than computation (or whatever smartphone battery life tests say)?

Oh what a perfect find. I have on my todolist to add POW to some of my api endpoints

I've had that idea for years.

Two versions that I experimented with. One is where the incoming POW hashes contribute to hashing power for some blockchain mining. An alternative "pay as you use the API" system.

The other using hashcash. Just a way to slow down abuse.

Both, however, suffer from the downside that many/all "ASIC resisting crypto mining" suffer from as well: the cheapest CPU power is CPU power from machines/power you don't own. Botnets, viruses, trojans etc.

So such a mechanism to throtthe or protect APIs won't hold back spammers and abusers for long.

Dirty energy is (often) cheap, so that's the energy the bad actors will use. I don't know that incentivizing bad actors to waste energy in a climate crisis is the best way to fight this problem.

You might correctly claim clean energy is often cheaper, but you must also consider the regions in which they'll get away with nefarious activity, and whether those areas have made the investments into making clean energy cheap.

I was specifically talking about "ASIC resistant crypto mining".

>Dirty energy is (often) cheap, so that's the energy the bad actors will use

Hmm, I don't get this, surely all actors will want the cheapest energy, no? The problem being the underlying one, that the dirty energy doesn't pay its externalities and is thus cheaper than renewables.

My guess is most bad actors will just use stolen energy (your computer with a botnet on it).

I'm not sure whether that's genius or horrifying. On the one hand, that could form the micropayments network the web always needed. On the other hand, it would enable quite a bit of abuse on its own.

or https://altcha.org which is easier to integrate ;)