HMAC is intended to be fast, which makes it ideal for crackers. For passwords you want something deliberately slow. Bcrypt is one such function, and it can be tuned to be even slower if you prefer.
For example, you can crunch through potentially a million passwords per second using a GPU-accelerated rig and software like HashCat if it's just HMAC-SHA3.
Bcrypt with default settings is around 13K per second on the same hardware. It's hundreds of times slower, plus you can increase the factor which can make it even slower still.
When protecting passwords you need to consider how long you need to keep them protected. Eventually every hashing method will be compromised, MD5 and SHA1 have been effectively beaten. By using a stronger Bcrypt setting you can make it harder to crack passwords on not just today's hardware, but hardware that exists ten years from now, protecting your application against future attacks.
Twenty-five years ago when using SHA-based password hashes it was inconceivable that a consumer-grade GPU could have several thousand threads, that would be more powerful than any supercomputer on the planet at the time. What hardware will exist twenty-five years from now? What if having a half-million threads is considered no big deal?
As much as twenty-five years seems like a long time, what if ten years from now your app gets hacked, and ten years after that the database starts floating around as part of a Torrent? Those passwords might still be in use, some people are really bad at changing them, which means you've got a responsibility to do your best to protect them.
There's a lot to understand here, but this post covers a lot of ground.
Yeah, I used HashCat to attack a Bcrypt hash before. I could do roughly 10-11 thousand attempts per second.
You did take note I wasn't just HMACing and encrypting the password though, right? I don't want any confusion. I was using a password hashing function.
That's what makes Bcrypt so great. Smashing through a dictionary against a compromised database is painful, and you can make it even more painful by cranking up the difficulty factor. It's very resistant against brute force attacks.
HMAC is meant for other things, like signing, where you're not dealing with brute-force attacks, where instead performance, authentication and verification are what matters. It's not in any way intended for, nor suitable to use as a password hash.
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