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Date: Sat, 25 May 2019 17:27:20 +0200
From: Solar Designer <>
Subject: Re: exact performance of supported ztex board for WPA/PSK cracking

On Fri, May 24, 2019 at 06:28:32PM +0200, Johny Krekan wrote:
> Thanx for information, so for cracking WPA PSK can John use other than GPU 
> acceleration if yes what devices?

For practical purposes, it is just GPUs and CPUs.  Theoretically, it is
also any other devices for which you have an OpenCL backend.

> GPUs are very temperature-intensive.

You can underclock GPUs or reduce their power limit (where supported),
or with our latest release (or bleeding-jumbo) you can also set a
maximum temperature that JtR will try not to exceed by adjusting the
duty cycle.  Of course, this hurts performance.  From the NEWS file and
the release announcement:

- Graceful handling of GPU overheating - rather than terminate the process,
  JtR will now optionally (and by default) sleep until the temperature is below
  the limit, thereby adjusting the duty cycle to keep the temperature around
  the limit.  (Applies to NVIDIA and old AMD drivers.  We do not yet have GPU
  temperature monitoring for new AMD drivers.)  [Claudio, Solar; 2019]

The corresponding john.conf settings are:

# Abort the process or sleep for a while if a GPU hits this temperature (in C)
AbortTemperature = 95

# Instead of aborting, sleep for this many seconds to cool the GPU down when
# the temperature hits the AbortTemperature value, then re-test the temperature
# and either wake up or go to sleep again.  Set this to 0 to actually abort.
# Suppress repeated sleep/wakeup messages when SleepOnTemperature = 1,
# we are interpreting this as intent to keep the GPU temperature around the limit.
SleepOnTemperature = 1

So you just change the 95 to a lower value according to your preference.


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