Is my plan a good idea?

[Saint]

Rainbow tables don't actually store the hash value, they store hash chains using a reduction function. So you still have to do quite a bit of calculation and false-alarm checking to look up a hash in a rainbow table, it is by no means instantaneous. And it does not scale well; the more hashes you have, the slower it gets. Rainbow tables are slow as shit with e.g. 20k hashes.

For much faster lookups you could store the hash (hopefully as a binary blob) in an indexed database. The tradeoff here is significantly more disk space since you're not using any reduction function, and it still won't be incredibly fast since your index will be way too large to hold in memory. If you don't care about disk space and have a few months you can spend running your laptop 24/7 to generate and index this table, then this would probably be what you'd want to do.

But again, I can't stress enough that this is a very silly solution to your perceived problem. It would be much better to just run straight dictionary attacks against fast hashes on your CPU, and leave your GPU to do more advanced high-yield attacks. And it doesn't really matter that you only have a laptop with a weak CPU and GPU. Several members of Team Hashcat got their start with only a netbook with an embedded CPU and no GPU, and have been more successful than people with multiple high-end GPUs because they are smart about their attacks.

And remember, quality over quantity. Most wordlists you download from the Internet are going to be pure garbage, and the larger it is the more garbage you're going to have in there.

Thanks for enlightening me on how a rainbow table works, I wasn't quite sure.

I have made a couple of wordlists myself, one being small, made up of a few small leaks, including, myspace, twitter and 10k most common passwords. Also a bigger one.

http://forum.insidepro.com/viewtopic.php?t=34386

Feel free to try it out.

What I find weird is, my CPU doesn't seem to be at its full potential. On a straight wordlist run, it says ~20 MH/s, but it only seems to run at ~10 MH/s. My wordlist has 302M words.

302,000,000 / 20,000,000 = 15

However it takes 27 seconds to complete. When running through a list of 45k hashes it takes 42 seconds. Which is ~7 MH/s, although it displays an average of 10 MH/s.

Threads: 4
Segments Size: 64MB
i5-2450M

Is there a bottleneck? Maybe my hard drive?