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Date: Fri, 5 Aug 2016 10:19:52 -0400
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Subject: Re: [RFC][DISCUSSION] Argon2 Password Hash
From: fsb@thefsb.org (Tom Worster)

On 8/5/16 8:47 AM, Charles R. Portwood II wrote:

> The RFC is available at: https://wiki.php.net/rfc/argon2_password_hash.

Hi Charles,

Thanks for doing this. I'm glad Argon2 is coming to PHP.

You can have a longer voting period if you like, which I think would be
a good idea.

I think it's confusing to have two consts to identify the algorithm. I
don't understand the analogy to PASSWORD_DEFAULT. If we only provide
Argon2i, one const is easier. If we anticipate adding another Argon2
algo in the future that is not backward compatible with this one then I
don't think we would want to change PASSWORD_ARGON2 to point to it.

Finally, I wonder if it wouldn't be better if, for the time being, we
do not provide default costs constants. Argon2 is new (as crypto algos
go) and very early in a gradual introduction in deployments. And it is
hard to use because of the three cost factors. Correctly tuning those
for different machines is not yet a commonly-understood skill. (You
even can find conflicting advice on how to tune Bcrypt's time factor.)

If we offer default costs then it will appear, to some people, even
those who know little about it beyond the name, as though deploying
Argon2 is just a matter of using it with the defaults. I'm not sure
this is a good idea.

If, on the other hand, we omit the constants and require the $options
argument then it discourages inexpert users. At the same time it
encourages experimentation and understanding of the costs, among those
who take an interest, which I think is just what we want.

Those who want to use Argon2 are going to make special efforts to get
the lib and enable it in PHP. So I don't think it's unreasonable to
expect the early adopters to give some thought to the costs.

Tom