phc-discussions - Argon2d nit picks

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Message-ID: <CAOLP8p6=w7hhAU=XTYBQws1CjnDpuJ0oNLcCOdUk52LV71+xyg@mail.gmail.com>
Date: Wed, 22 Jul 2015 09:25:10 -0700
From: Bill Cox <waywardgeek@...il.com>
To: "discussions@...sword-hashing.net" <discussions@...sword-hashing.net>
Subject: Argon2d nit picks

Now that it's the winner, it's time to point out minor flaws.  I did a
quick read through the reference code, and some of the opt code.  Here's my
notes:

Argon should return an error code when output > MAX_OUTLEN (currently 2^32
- 1).  Currently, it fills only MAX_OUTLEN bytes, and returns success.
Similarly, return error codes for msglen, noncelen, secretlen, adlen, and
m_cost when they are too long.  What is ad?

Rename msg to passwd or password.  There is no way to know that msg means
the password otherwise.

What is ad?  If it is not clear just reading the code, that's a problem.

Why is the max secret size 32?  Why not be variable, like the password?

Line 321: comment is out of date.  Minimum t_cost is now 1: //minimum
t_cost =3

Code should be reformatted to conform to a popular standard.  For example,
this is not cool:

    }
    else prev_index = BLOCK(lane, slice, i - 1);

Argon2d borrows more from TwoCats than I realized, such as 4 sync points
for multi-threading, in addition to the 1-pass architecture.  I approve :-)
 It should also borrow they hybrid model, unifying Argon2i and Argon2d.

Optimized and reference code do not clear any secret parameters, making it
vulnerable to garbage collector attacks.

Bill

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