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I've been reading up on RAM Disks and their roles in various uses. The role one no one talks much about is password cracking. I pulled the below quote from here

"It's also important to know that hard drives (the magnetic, rotating disk variant, anyway) have access times in the millisecond range. RAM is orders of magnitude faster, but still slow compared to L1 cache, which again is much slower than direct register access in a CPU. Unfortunately, general purpose CPU registers can only store maybe 128 bytes in total, and L1 cache only stores a few kb in total. "

Let's assume the password file is 3.9 GB and we have a 4 GB RAM\tmpfs Disk\volume. So my question is, would creating a RAM Disk OR a tmpfs volume (linux) and then putting said password file on that virtual disk offer any tangible increase in speed. So my question is, would creating a RAM Disk\tmpfs volume and then putting said password file on that virtual disk offer any tangible increase in speed? Does the cache play any role in this besides storing the hash file and would it help to store the hash on the RAM/tmpfs disk too? Also would the difference be lessened is the user were reading the password file of a SSD instead of a hard drive?

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Most likely not.

Password cracking is a computationally-bounded operation. Modern SSD and hard disks can read way beyond the number of hashes you can do with current CPU/GPU.

Additionally, all modern operating systems will do read ahead buffer and file caches automatically, so most of the time you'd be reading from RAM already.

I once ran john-the-ripper with a large piped word list like so with apr1 hashes:

pv wordlist.txt | john-the-ripper --pipes --rules hashes.txt

pv is a tool similar to cat, but it can calculate and show you the speed of data going through your pipe. Most of the time, you'll notice that the pipe is stalled.

If you used a fast hash and you have a cracking cluster with very large computational power, then the speed of reading the file could possibly affect the cracking speed more, but it's quite unlikely that the speed of the disk would be your first bottleneck.

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