I think that's the problem here: Bitwarden hashes the passwords on the client side but it runs on various client devices, some more powerful than others, and others not able to run efficient Argon2 implementations.
Citing the OP:
>Sure, you might tolerate a longer unlock time, but is the security gain really worth the cost to your battery?
I think the battery concern is over-blown. How often do you login into a service? I think that for typical use-cases, amortized battery-cost of a login is negligible. And for other use-cases you can let users choose.
I don't see any issues with that.
Via the master-key, the program derives(locally) the key to encrypted the data and a different secondary key for authentication against the server. without knowing the master-key you can't decrypt the vault even if you were able to trick the server into sending you the vault.
The vault is decrypted locally
No. Master key doesn't leave client machine, only its hash is transmitted over the network. See dchest's link above.
Like what? It looks like personally my phone is 4x slower than my desktop. So if I calibrate for one or two seconds on my phone, the security should be pretty acceptable. Do I need to worry about devices much slower than that?
I don't think a 3s wait for a session, for greater security, and that on an unoptimized device is going to be breaking UX.
The submitted github comment also makes that point, this is actually hard to do.
Choice is always better. for people who care\worry, they can change to something more resistant to cracking.
Users will forget their Master Passwords even and because they forgot them they will believe they've been "hacked" and blame you.
Users on Hacker News and similar sites where users actually understand the underlying technology to some degree are the exception, not the norm. Adding options does not help a vast majority of the user base and it complicates your codebase further. Imagine making that change and less than 1% of your users actually use that feature?
You're thinking wrong.