I am going to be hashing user passwords on the client machine, and I would like the hash to be generated in 0.3 seconds.
Do I need to find the number of rounds myself and make every user use this number, or should the number of rounds depend on the machine?
For example, if I found that 10 rounds took 0.3 seconds on my machine, does this mean every user should use 10 rounds? Or should it be on a per-machine basis. If it's per machine, I will have to send the number of rounds to a server and store the number of rounds on the user machine to make sure this number is always used in the future. Is that ok? Or do things not to be that complex?