Date: Tue, 27 Feb 2018 23:11:53 +0100 From: Solar Designer <solar@...nwall.com> To: john-users@...ts.openwall.com Subject: Re: Getting full performance out of multiple GPU's 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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