Date: Tue, 27 Feb 2018 17:36:15 -0600 From: Adam Lininger <arlininger@...il.com> To: john-users@...ts.openwall.com Subject: Re: Getting full performance out of multiple GPU's Thanks Alexander. That gives me a much better understanding of how JtR does things internally also. I believe I will have much better luck with this guidance. Adam On Tue, Feb 27, 2018 at 4:11 PM, Solar Designer <solar@...nwall.com> wrote: > On Tue, Feb 27, 2018 at 03:59:44PM -0600, Adam Lininger wrote: > > Thank you for the help. I believe I am properly using a GPU and the > actual > > hashing is being done there. The nvidia-smi command seems to agree. Based > > on your email, I suspect the problem is that the korelogic rule > generation > > is still happening on the CPU rather than the GPU. Is there an easy way > to > > correct that? I've copied my command below. > > > > john --wordlist=rockyou.dict --format=descrypt-opencl > > --devices=1,2,3,4,5,6,7,8 --fork=8 --rules=korelogic htpasswd > > Yes, it's one of those cases where you'll have to use --mask, and this > prevents you from using solely the KoreLogic rules - at best, you may > add a mask on top of them, but a mask would push many candidates beyond > the length of 8, which is the maximum for descrypt, making this approach > not entirely reasonable. > > You may have better luck running the rules against your descrypt hashes > on CPU, and using your GPUs for something like: > > john --incremental --mask='?w?a?a?a?a' --format=descrypt-opencl > --devices=1,2,3,4,5,6,7,8 --fork=8 htpasswd > > This will output something like: > > Loaded 1 password hash (descrypt-opencl, traditional crypt(3) [DES OpenCL]) > Warning: MaxLen = 13 is too large for the current hash type, reduced to 4 > > The warning is OK - it means that JtR correctly reduced incremental > mode's maximum length to 4 due to descrypt's maximum of 8 and mask of 4. > > You could also want to use the --min-length and --max-length options to > split this into several invocations of JtR varying by length (perhaps > from 5 to 8), so that you keep track of what lengths have already been > exhausted vs. not yet. You'll probably complete lengths up to 7 > inclusive within a day, and then focus on length 8 for some days more > (if for one hash; otherwise multiply by the number of different salts). > > Alexander >
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