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Date: Sat, 21 Nov 2020 14:09:53 +0100
From: Solar Designer <>
Subject: Re: Session management on AMI - Interrupting and resuming


On Fri, Nov 20, 2020 at 03:56:53PM +0100, Solar Designer wrote:
> On Fri, Nov 20, 2020 at 10:01:38PM +0900, SQP Admin wrote:
> > We are currently running an Openwall Amazon AMI, running an incremental 
> > session on a ZIP archive. We have chosen to go with a c5.24xlarge 
> > infrastructure and using multiple CPU threads like so:
> > 
> > john --session=XX --incremental=Alnum --fork=96 xxxx.hash
> > 
> > We are in a situation where we expect getting a correct guess will take 
> > some time and also have budget restrictions. We understand sessions can 
> > be interrupted and resumed using the --restore=[sessionname] option. Here 
> > are my questions:
> > 
> > 1. Is the approach we've taken to take advantage of the 96 CPUs correct? 
> > (--fork=96) - or is there a better way of leveraging that instance 
> > performance?
> The approach you've taken is probably optimal, but we need to know
> whether your archive is of PKZIP (fast) or WinZip (slow) kind.  For
> PKZIP, "--fork" is certainly the way to go.  For WinZip, OpenMP works
> well enough and is more flexible (allows you to adjust thread count on
> restore) and enables incremental mode to test passwords in a slightly
> more optimal order.

Actually, for WinZip you'd have better speed and performance/dollar on a
GPU in p3.2xlarge.  So I assume/hope you have a PKZIP archive, for which
"--fork=96" on c5.24xlarge is appropriate.


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