I use dovecot as my mail transfer agent and I aim to use the strongest password scheme which is supported by my system: SHA512-CRYPT or SHA256-CRYPT (BLF-CRYPT doesn't work).
For my own written webinterface I look for a function or library in node.js for hashing a password (with SHA***-CRYPT).
You may consider checking: https://github.com/mvo5/sha512crypt-node which contains a implementation for sha512crypt in JS. Its very new but passes the testvectors from the glibc reference implementation.
Check out my fork of shacrypt - a Node.js addon that supports SHA-256 crypt and SHA-512 crypt password hashing.
I extended it to:
Support asynchronous operation where computation is performed in Node.js's libuv thread pool, so it won't block the event loop.
Allow the module to be built under Windows
You will need to have C++ build tools installed on your system to successfully install the package. If you are running under Windows, you can download Microsoft's Build Tools for Visual Studio 2017.
Have you seen this page: cryto.createHash sha512 with hexDigest input type
You can use crypto.createHash function, but why SHA512? Are you sure you need it for your website?
