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Best Hardware for bcrypt - Printable Version

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Best Hardware for bcrypt - ArnoNym - 03-21-2025

Caio
I am looking to rent hardware for a little hash encryption.
I have a bunch of bcrypt hashes (around 500) with workfactor 10 and mostly 12.
Atm. i am using wordlists and "oneruletorulethemstill".

Until now i used my own hardware but for educational purpose and because i am interested in the efficiency of new hardware i am thinking about renting hardware from vast.ai (or similiar)

So what is the best hardware (i expect a gpu) to use for bcrypt hashing?

So far i was looking up some benchmarks for:
  • H100 pcie: 251kH
  • A100 pcie: 130kH
  • V100: 52kH
  • RTX 5090: 250 - 300 kH/s
  • RTX 4090: 184kH
  • RTX 3090ti: 103 kH
  • 6000ada: 23kH
  • L40S: 178kH
But i realized that these benchmarks are not always the real situation cause of lack in memory of the gpu and decreasing hashSpeed after a few seconds/minutes in bcrypt hashing.

Thanks for your recommendations and kind regards

RE: Best Hardware for bcrypt - DanielG - 03-21-2025

The benchmark uses workfactor 5. Going from workfactor 5 (32) to workfactor 10 (1024) is a 32 times increase (32*32=1024). Meaning that cracking will be about 32 times slower. Workfactor 12 (4096) is again four times slower.

So you will need to divide all your benchmarks to get real cracking speeds. See post https://hashcat.net/forum/thread-12524.html about someone getting only 1kH on the RTX 5090.

After this you will need to think how large your search space is going to be. If you want to crack passwords of a length of 6 (uppercase, lowercase, numbers and no special characters) a RTX 5090 for the workfactor 10 hashes is going to take 1800 years.

RE: Best Hardware for bcrypt - ArnoNym - 03-21-2025

Hey Daniel
Thanks for your explanation.
I know that the benchmarks I mentioned are for workfactor5 and that 10 or even 12 will be much slower.
The minimum password length is 8 characters and i know that bruteforce is not realistic.

Luckily i dont want to get one cleartext from one hash.
I am rather looking how many cleartexts i can "guess" using wordlists.
And i think i got a good wordlist from hashmob.

But now i wanted to ask the hashcat community which hardware would be best to use for my purpose.
i already tried my own hardware and realised it is very slow.
So i want to know what hardware would be better/best and how far is this hardware pushing the speed in my specific case.

Thanks for further answers

RE: Best Hardware for bcrypt - ArnoNym - 03-25-2025

Noone else has recommendations about good hardware for bcryp?
Which gpu has more or faster caches, rather many gpus or one powerful gpu?
Something?

RE: Best Hardware for bcrypt - slyexe - 03-26-2025

You are asking what is the best hardware for bcrypt but yet you've already been given an answer. The follow up question of asking whether to use 1 or multiple gpus is irrelevant, you know which is the best hardware its just multiplying the hashrate by X amount of GPUs you want to use. There's not much else to tell you, bcrypt is slow so the more power you throw at it the sooner your wordlist will finish.

RE: Best Hardware for bcrypt - ArnoNym - 03-26-2025

Thanks Smile

RE: Best Hardware for bcrypt - ArnoNym - 03-26-2025

After a while of playing around with differen vast.ai GPUs i dont think it is that easy anymore.
I would be glad if someone could help me answering this questions:
  1. I have one instance with 4 times RTX 3080 wich is shown as 117.0 TFLOPS which runs my bcrypt hashes with 840 H/s = 3360.
    Another instance with 8 times RTX 2080ti is also shown as 117.0 TFLOPS but each instance is at 343 H/s = 2743 in Sum.
    For me it looks like it is not just a matter of "power" but also some other specific criteria. someone know more about this?
  2. I run an instance of the rtx 4090 which was very powerful (7k H/s) for one hash and a big wordlist.
    But the same instance/hardware was just at 2k H/s when i used it with 90 hashes and the same wordlist.
    Why isnt hashcat just going through the hashes one by one if it would be almost 3 times faster if you look at the H/s?
  3. And as far as i know bcrypt hashing has some specific hardware requirements (it needs alot of vram?). Thus i would ask the same question again: Is it better to use one powerful hardware that has alot of vram or is it more effizient to use alot of less powerful GPUs because they have the better "storage" ratio?
  4. Does anyone have a similiar scenario or knowledge and can recommend hardware for this usecase (alot of hashes, wordlist attacks and a workfactor of 10 and 12)?
    What about the datacenter GPUs A100 and H100 are they better/more effizient than RTX GPUs?
    And for the RTXs are the higher generations more efficient than a bunch of lower generations?

Thanks for sharing your expierence and best regards

RE: Best Hardware for bcrypt - Chick3nman - 03-28-2025

There is no good hardware that's readily available for bcrypt. That's sorta the point, the algorithm was designed to try and ensure this was the case.

As for your specific case, 4090s are the fastest cards you will be able to find and rent, and likely the most cost efficient as well. The speed issues you are seeing are likely related to mixed cost factors in the same hash file, or perhaps some workload tuning issues. All in all, 2kh/s doesn't sound that bad for what you are doing and if that's not enough, 7kh/s is certainly not going to be enough either. At these speeds, you're not going to get much from switching hardware, as even if it doubles your speeds, most attacks are still going from "completely infeasible" to "still completely infeasible". I would simply stick with the 4090s and work on optimizing your attacks and methodologies, as that's going to be required regardless of the hardware you end up with since there is nothing readily available that will give you vast improvements in speed.

Unfortunately, what you are trying to do is something most people simply don't even attempt due to how slow and constrained it is and how hard it will be to crack almost anything. Those of us who do work with hashes this slow have spent a very long time working out attack optimizations and hardware solutions and despite all that work and sometimes significant financial investment, it's STILL incredibly difficult to work with bcrypt.