Date: Fri, 13 Jul 2018 11:56:18 +0200 From: Solar Designer <solar@...nwall.com> To: john-users@...ts.openwall.com Subject: Re: Need info - multiple hashes On Fri, Jul 13, 2018 at 12:05:57PM +0530, Sudheendra S S wrote: > Need help - If the input file to john contacts diff type of hashes (MD5 > Crypt, DES, Blowfish), would john try to crack all hash types? I am trying > to input shadow hashes from multiple servers with diff OSes (Suse/RHEL). Usually not. John will tell you that there are multiple hash types and what "--format" options you may use to request testing of those other types. Then you need to run one session per hash type. It is OK to run those multiple sessions simultaneously, including in the same directory. Just give them different "--session" names and don't exceed your total logical CPU count. Limit each session's use of logical CPUs (with OMP_NUM_THREADS environment variable and "--fork" option parameter, which are multiplied) such that the total isn't greater than what you have supported in hardware. For example, on a machine with N logical CPUs, you could set OMP_NUM_THREADS=1 in all invocations and split N across the "--fork" counts for your different sessions, or you could do it the other way around with OpenMP thread counts adding up to N (or a bit less if the machine isn't otherwise completely idle) and then don't use "--fork". For those hash types you mention, there's a trick that will make John crack them simultaneously: "--format=crypt". But it will result in much worse performance, both in terms of code efficiency (system-provided not-so-optimized password hashing code will be used) and in terms of (not) proceeding further to more complex passwords for faster ones of the hash types (the overall progress will be limited by the slowest hash type, so you will miss easily crackable passwords of the faster hashes). Alexander
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