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Date: Sun, 20 Jul 2014 09:36:13 +0400
From: Solar Designer <solar@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: ZedBoard: bcrypt

Katja,

On Sun, Jul 20, 2014 at 06:48:57AM +0400, Solar Designer wrote:
> I've just added a 40mm 12V 0.08A fan connected at 5V.  I tried several
> of these 40mm 12V fans, and chose one that most reliably spins up at 5V.
> I think when connected like this it consumes under 0.5W (maybe 0.3W).

This wasn't good enough.  Although individual tests like the below
passed, two of them in a row (without delay) resulted in a reboot.

I've reconnected the fan to 12V, and so far 30 tests in a row passed
(more than an hour total).  I'll probably interrupt further testing.

The easiest place to take 12V from appeared to be the J21 "current
sense" jumpers.  Unfortunately, this breaks the "current sense" for its
intended functionality (measuring the board's current draw at 12V) since
the connector itself has resistance way in excess of the 0.01 Ohm that
is used for the current sense, so the voltage across these two jumpers
is dominated by the extra current going to our fan.  Without the fan, I
measured 5.8 mV at idle, 7.0 mV when running this test.  These are
with the Epiphany FMC plugged in (would be ~2 W lower without it).
These translate to:

0.0058/0.01*12 = 6.96 W
0.0070/0.01*12 = 8.40 W

so the idle to load delta is about 1.44 W.  (BTW, this is about 1.44 A
extra at 1.0 V, which slightly exceeds that voltage regulator's maximum
of 1.3 A according to docs for ZedBoard, but is below the 2 A maximum
specified for this output of the Maxim chip.)

With the fan abusing one of J21 pins to take 12V from, I get ridiculous
readings like 25 mV or -15 mV (yes, negative, which is easy to explain),
depending on which of the two pins I connect the fan to.

The fan should be consuming about 1W now.

> root@...aro-ubuntu-desktop:~/k3/JtR_112/JohnTheRipper/run# ./john -i=digits4 ~solar/pw-bcrypt-12-64 
> Loaded 64 password hashes with no different salts (bcrypt [Blowfish 32/32])
> Press 'q' or Ctrl-C to abort, almost any other key for status
> 1                (?)
> 12               (?)
> [...]
> 46               (?)
> 47               (?)
> 64g 0:00:02:46 0.3848g/s 64.65p/s 64.65c/s 2477C/s 282..275
> Use the "--show" option to display all of the cracked passwords reliably
> Session completed

Alexander

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