phc-discussions - Re: [PHC] Is bandwidth all that counts?

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAOLP8p5UgQoEWnReu9Xb3fDBEp+m-k3XE1KrKjAJq5yeR1arFQ@mail.gmail.com>
Date: Wed, 12 Feb 2014 13:58:12 -0500
From: Bill Cox <waywardgeek@...il.com>
To: discussions@...sword-hashing.net
Subject: Re: [PHC] Is bandwidth all that counts?

On Tue, Feb 11, 2014 at 5:50 PM, Andy Lutomirski <luto@...capital.net> wrote:
> The attacker will need more memory, right?  Interleaving between
> different passwords increases bandwidth, but it proportionately
> increases the amount of memory needed, I think.
>
> --Andy

Yes, and that makes his system more expensive.

If a user has a reasonable time limit of 1 second of patience for
hashing 4GB of memory (write once, read once), an attacker will need
around 4GB per guessing core.

I did a bit of googling to see how cheaply I could build a 4GB DDR3
10GB/sec guessing unit.  I think it can be done for around $100 with a
cheap low-end GPU and 8GB of cheap DDR3 memory.  DDR3 is running about
$10/GB, and low-end GPUs to match seem to be around $35.  There is
still cost for the board, capacitors, power supply and I/O interface,
so I think $100 is about right.

At that price, we'd have guessing hardware costs of about $100 per
guess per second for NoelKDF guessing hardware, which isn't bad, but
it's still 5X cheaper than my son's home-built Linux MineCraft server.
 I really do think memory bandwidth is where the metal meets the road
and where we'll draw the line in the sand against brute force attacks.

Bill