Improve security of weak passphrases by implementing PBKDF2

[NxtChg]

Users often pick low-entropy passphrases, because they are used to regular passwords.

And then their account gets hacked with something that looks like offline bruteforcing.

So instead of doing

MessageDigest.getInstance("SHA-256").digest(secretPhrase.getBytes("UTF-8"))

we should do something like PBKDF2 to improve security.

[Jean-Luc Picard]

Whatever gets done in the javascript client has to be supported in other clients too, so that when the js client is dropped users have a way to migrate. So only if PBKDF2 becomes standard in at least a few alternative clients, and if we still maintain the js client at that time, then it would make sense to also add PBKDF2 to the js client.

[NxtChg]

No argument there.

I will continue nagging client devs to agree on some sort of standard for this.