Date: Sun, 25 Nov 2018 17:24:57 +0100 From: Frank Dittrich <frank.dittrich@...lbox.org> To: john-users@...ts.openwall.com Subject: Re: Chunk of work specification Hi all, I just noticed that I accidentally sent a direct reply (prior to Alexander's replies) instead of replying to the list, so I'll just send the same information to the list... Am 24.11.18 um 10:02 schrieb Vojtěch Večeřa: I know that JtR has --node parameter but it doesn't seem too > intuitive nor precise when it comes to the exact sizes of chunks. The trouble is, even if you had chunks of exactly the same chunk size, some might be much faster than others, e.g., because some chunks crack many passwords, while others don't. (For fast hash algorithms, writing the cracked passwords into the pot file and logging the crack in the log file will have a measurable performance impact.) But you don't easily (i.e., without a measurable performance impact, at least for faster hash algorithms) get chunks of the same size for many cracking modes. Even for simple --wordlist mode with --rules, where you could define chunks of the same size, real work depends on how many of the rules get rejected (e.g., because the hash algorithm isn't case sensitive), or how many words from the word list file will get rejected, e.g., because they don't contain a letter a, e, o, i, l, etc. (So, a node which gets a large chunk of l337 rules will be much faster than others, because the amount of actual work is smaller.) For incremental mode, the chunk sizes will vary depending on password candidate length and the character count. In general, the chunk sizes will get larger the longer you run incremental mode. If you want to use --incremental mode with slow hash algorithms, you could look into john's Parallel external mode, adjust it accordingly, and run --incremental combined with a different --external=... mode on each of your machines. For faster hashes or a large number of nodes, you'll just waste a lot of CPU time, because each john instance will generate all the password candidates, but reject all but 1 out of N candidates in --external mode. (But you'd definitely get chunks of the same size.) Frank
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