phc-discussions - Re: [PHC] Specification of a modular crypt format

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Date: Sun, 20 Sep 2015 17:18:40 +0000
From: Jean-Philippe Aumasson <jeanphilippe.aumasson@...il.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Specification of a modular crypt format

Great, thanks Thomas, will review.

If the code turns out to be a formal reference it'll need to mention your
copyright and any public domain-like license you like (CC0, WTFPL, etc.).



On Sat, Sep 19, 2015 at 7:03 PM Thomas Pornin <pornin@...et.org> wrote:

> Hello,
>
> here is some example C code that implements encoding and decoding of
> hash strings for Argon2i.
>
> According to the remarks made here, I followed rules that differ from my
> earlier draft in the following respects:
>
>  -- The decoder does not validate input strings; it may accept strings
>  that do not comply with the specification (e.g. "p=01" instead of
>  "p=1").
>
>  -- I am using "normal" Base64 (not the crypt variant), although I do
>  not include the '=' padding signs.
>
>  -- I added two optional parameters "keyid" and "data", that correspond
>  to an identifier for the key (if any), and associated data. Both are
>  binary (encoded in Base64); the key ID is up to 8 bytes, while the
>  associated data is up to 32 bytes. When they are empty, they are omitted
>  (i.e. there is no difference in encoding between "no associated data"
>  and "associated data has length 0").
>
>  -- I set the parameter order to "m, t, p, keyid, data".
>
> The code includes some generic Base64 encoder/decoder (about 150 lines),
> then code specific to Argon2i (about 200 lines), and some test vectors.
> The Base64 code is constant-time with regards to the data contents (no
> data-dependent table lookups or branches); this is probably useless in
> most situations, but easy enough to achieve.
>
>
> This sample code is meant to give some discussion basis about
> implementation complexity. Feel free to reuse under "public domain"
> rules (i.e. do everything you want except blame me).
>
>
>         --Thomas Pornin
>

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