Is it too early to be suggesting Argon2? I've not heard of it until now, but the Wikipedia entry[1] shows that the paper was just released late last year.
Most environments don't have an implementation for it yet, and the ones that do will probably only get it through libsodium for the first few years.
> I've not heard of it until now, but the Wikipedia entry[1] shows that the paper was just released late last year.
Argon2 was the winner of the Password Hashing Competition, a several-year cryptography competition to find a new password hashing algorithm that would be secure against an attacker armed with a large GPU cluster.
The judges included a lot of famous cryptographers and security experts. Of particular note: Colin Percival, the author of scrypt, and Jens Steube, the project lead for hashcat.
I've read the paper and I think Argon2 will stand the test of time, but I could (of course) be wrong.
Most environments don't have an implementation for it yet
Disclaimer: I wrote the Ruby one.
When I started looking through the node bindings, I found a number of minor bugs and a critical issue that left ~1% of passwords vulnerable.
I trust that the C developers do a good job, but phc-winner-argon2 does not appear to have ever made a formal release. Is master really always perfect?
It's not ready yet.
Don't do it yourself.
Define X as the maximum time you can allow a hash to run on your server, before it either starts to annoy users, or becomes a DoS issue. Moving from "Argon2, such that it runs for X" to "both algorithms, with a total cost X" means both of them are running with a much reduced work strength.
In the case of Argon2, there is an "iterations" counter, but t=2 is already reasonable, and on low end hardware, you may see t=1. So as per the spec, reducing runtime in order to make whole thing work is going to involve reducing m.
Except bcrypt is already not memory hard, and you've just reduced the only memory constraint in your algorithm.
And entirely possible there are bigger issues I didn't up with two minutes of thinking about it.