BCrypt + GTX670 = 6 c/s?

[gat3way]

Look at the speeds for bcrypt on http://hashcat.net/oclhashcat-plus/ under "Performance". A Radeon 7970 gets 4020 c/s and nVidia GTX 580 get 1618 c/s which should be similar to a GTX 670 going from the chart @ http://www.gat3way.eu/est.php

That's what I initially was hoping for. The GPU's are broadly speaking in the same weight category, so why the roughly 600x difference in performance.

Never tried to crack bcrypt on NV but if you change the number of hashes the speed should change. If you take a greater wordlist and the speed improves you tried a to small dictionary.

So basically, trying one hash at a time with a bigger (say, rockyou.txt) wordlist should make a difference? Will report. JFYI, I used the wordlist from JtR just to get a benchmark off my newly bought GTX.

Thanks for all the input, will update as per results.
Anton.

Hello Anton,

What atom meant is that attack depends on the number of hashes you are trying to attack (this correlation is linear, e.g attacking 5 hashes will yield 1/5 of the attack speed).

Another reason for the slow speed could be the iterations count which is "embedded" in the hash string. I guess you could post the hash prefix and that's not against the forum rules, but basically the bcrypt hashes look like:

$2$<iterations>$<salt>$<base64-encoded hash>

The common hashes have "5" for iterations (which actually means 2^5=32), so they start with $2$05$

However some implementations might increase the iterations count.

Keep in mind that bcrypt is quite an anti-GPU algorithm as it requires a lot of memory accesses. A mid-end CPU would often crack it faster as compared to a high-end GPU.