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Date: Sun, 7 Apr 2013 17:10:42 +0200
From: magnum <john.magnum@...hmail.com>
To: john-users@...ts.openwall.com
Subject: Re: What am I doing wrong?

On 7 Apr, 2013, at 15:50 , Sandra Schlichting <littlesandra88@...il.com> wrote:
>> The incremental and markov modes choose strings based on
>> likelihood/statistics rather than just iterating through every possible
>> combination in order. If the passwords are going to be over 8 characters,
>> you will have to re-compile john so that it's incremental mode will work
>> with more than 8 characters. Markov does not use the .chr files so it
>> wouldn't be limited or need to be compiled to support longer lengths but it
>> does have to be trained.
> 
> That is very interesting!
> 
> So Marcow can not be stopped and resumed. Can Incremental that?

Both can be stopped and resumed nowadays. The main practical difference between them is that while Incremental tries the most "probable" candidates first, Markov does not. So for Incremental, you just start it and run it for as long as you want but for Markov you need to choose beforehand how long you want it to run (by picking a suitable "markov level"). Within that given level, Markov will not pick better ones early.


> Can I ask a bonus question about compiling jtr?
> 
> I started the job on a "Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz"
> wjich have these "flags" as "cat /proc/cpuinfo" calls them:
> 
> fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36
> clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx lm constant_tsc
> arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl
> vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 lahf_lm dtherm tpr_shadow vnmi
> flexpriority
> 
> and compiled it by
> 
> wget http://www.openwall.com/john/g/john-1.7.9-jumbo-7.tar.bz2
> tar xjf john-1.7.9-jumbo-7.tar.bz2
> cd john-1.7.9-jumbo-7/src/
> make  clean linux-x86-64
> ../run/john --format=raw-md5 /tmp/hashs
> 
> Is that the correct architecture I have chosen?

I think so, but you may get slightly better speed with linux-x86-64i.


> Reading the FAQ, it seams that if I want to use both cores, then I have to
> hand schedule the jobs?

For raw-md5, yes (some slower formats can use OpenMP but not the raw ones) - either that or you can let MPI do it for you (see doc/README.mpi).


> Given that I have started the job with
> 
> ../run/john --format=raw-md5 /tmp/hashs
> 
> can I then stop it, split the remaining in two, and resume using both cores?

Theoretically, maybe. But I don't recall it having ever been described.

magnum

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