scrypt Smoketest

This is just a simple script to find which value of log₂(N) should use for the scrypt password hash on your machine. The paper recommends that each hash take ~100ms - we simply bench the hash for each value of N until we reach one that takes the recommended time.

Installation

Assuming you have the Rust toolchain installed, simply:

$ git clone https://github.com/slightknack/scrypt-smoketest.git
$ cd scrypt-smoketest
$ cargo run --release
Starting smoketest
...

The program will terminate after it finds a value of N which takes longer than 100ms/hash to execute.

So, what should N be?

I've heard that N should be anywhere from 14 to 20, but I wasn't sure which value to use in practice. Of course, these results will be different across machines; If you'd like to contribute the results of your tests, see the section below.

Here are the results for the machine I tested these benchmarks on, a 2015 MacBook Air with a 1.6 GHz Intel i5:

...
i = 13; 100 in 2397275310 ns; 23972753 ns/hash; 23.972753 ms/hash
i = 14; 100 in 4780038600 ns; 47800386 ns/hash; 47.800386 ms/hash
i = 15; 100 in 9491265365 ns; 94912653 ns/hash; 94.912653 ms/hash
i = 16; 100 in 19257962378 ns; 192579623 ns/hash; 192.579623 ms/hash
Smoketested up to i = 16, which took longer that 100ms/hash

Based on these results, I recommend you use N = 15 minimum, preferably higher. This is an older machine, so I doubt these results are fully relevant.

Help collect more results

If you'd like to clone this repo and run this smoketest on your machine (just make sure to --release it, y'all), I'd love to make a nice table or something. Just open an issue with the title Smoketest on <Computer Model> containing your results.

Thanks and have a wonderful day!
Isaac Clayton