oclHashcat (old version)

Note: all versions of oclHashcat have been replaced by a unified OpenCL CPU/GPU version, now known simply as hashcat.


oclHashcat is a GPGPU-based multi-hash cracker using a combinator attack.

Note: this is the old deprecated version of oclHashcat up to version 0.26, see oclHashcat-plus for newer version.

Current Version

Last Version was 0.26 before it was replaced by oclHashcat-plus.


Before oclHashcat, there was only the CPU-based hashcat version from the hashcat family. However, when hashcat was written there were already GPU crackers like EGB, CUDA-Multiforcer, IGHASHGPU or BarsWF. In terms of cracking performance, they totally owned hashcat. However they were not faster than hashcat in terms of how fast they could crack a hash. That is the big difference. Since these tools all used Brute-Force attack, it was nearly impossible for them to crack a 12-character long password. That is why the most efficient method of cracking passwords is dictionary-based. None of the GPU crackers were able to handle dictionary-based attacks.

After reviewing some sites/forums/blogs etc. to find out why there is no GPU cracker using dictionaries, it quickly turned out that they can not run efficiently because of the slow PCI-E transfer rates. That does sound logical (at least for the fast algorithms), but no one wanted to do a simple dictionary attack. Hashcat already handled that very well.

Dictionary-based does not always mean a dictionary attack. There is much more to it, like rule-based attack, toggle-case attack or combinator attack. Unlike a simple dictionary attack, these advanced-attack versions should run efficiently on a GPU program. That is because they can mutate the base words on the kernel and because of this, there is no need to execute slow PCI-E transfers.

After some weeks of effort, the first engine worked. It was capable of doing a combinator attack. This first version was written as a simple proof-of-concept version that shows how to efficiently use GPUs for dictionary-based attacks and was called “Combination-CUDA”. A video can be watched here: http://www.youtube.com/watch?v=cCD65oWts5I. This program was very limited. For example, it only supported NVidia GPUs, no Multi-GPU setup and could crack MD5 only.

The next step was to write a real program bundling all the experience gained from hashcat and combination-cuda development. This approach was called “hashcat+” (NOTE: not oclHashcat+), but it was never released to the public. The reason for this was that during the development of hashcat+ a new version of OpenCL was released by the Khronos Group. The cool thing about OpenCL is that it supported both NVidia and ATI/AMD cards. Actually both vendors added an OpenCL runtime to their drivers/SDK. To utilize it, it was neccessary to rewrite hashcat+ from scratch, since it was made for CUDA, not OpenCL. This new program was called “oclHashcat”.

With the release of oclHashcat the limitations of combination-CUDA have been eliminated.

The first official Combination-CUDA release was v0.01, released on 05.02.2010.

The first official oclHashcat release was v0.18, released on 01.05.2010.


Usage: oclHashcat [options] hashlist dict_left|mask_left dict_right|mask_right

  -V,  --version             print version
  -h,  --help                print help
       --eula                print eula

Logging and Files:
       --quiet               suppress output
  -o,  --outfile=FILE        outfile for recovered hash
       --outfile-format=NUM  0 = hash:pass
                             1 = hash:hex_pass
                             2 = hash:pass:hex_pass
       --remove              enable remove of hash from hashlist once it is cracked
  -e,  --salt-file=FILE      salts-file for unsalted hashlists

       --runtime=NUM         automatically abort session after NUM seconds

       --hex-salt            assume salt is given in hex
       --hex-charset         assume charset is given in hex

       --gpu-async           use non-blocking async calls (NVidia only)
  -d,  --gpu-devices=STR     CUDA devices to use, seperate with comma
  -n,  --gpu-accel=NUM       workload tuning: 1, 8, 40, 80, 160, 400 or 800
       --gpu-loops=NUM       workload fine-tuning if -n is not precise enough
       --gpu-watchdog=NUM    automatically abort session at NUM celsius

Built-in charsets:

  ?l = abcdefghijklmnopqrstuvwxyz
  ?d = 0123456789
  ?s =  !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~
  ?h = 8 bit characters from 0xc0 - 0xff
  ?D = 8 bit characters from german alphabet
  ?F = 8 bit characters from french alphabet
  ?R = 8 bit characters from russian alphabet

Custom charsets:
  -1,  --custom-charset1=CS  user-definable charsets
  -2,  --custom-charset2=CS  example:
  -3,  --custom-charset3=CS  --custom-charset1=?dabcdef
  -4,  --custom-charset4=CS  sets charset ?1 to 0123456789abcdef

Attack options:
       --increment           enable increment mode
  -j,  --rule-left=RULE      rule applied to each word from left dict
  -k,  --rule-right=RULE     rule applied to each word from right dict

Hash types:
  -m,  --hash-type=NUM       number correlates to hash-type

    0 = MD5
    1 = md5($pass.$salt)
    2 = md5($salt.$pass)
    3 = md5(md5($pass))
    5 = vBulletin < v3.8.5
  100 = SHA1
  101 = sha1($pass.$salt)
  102 = sha1($salt.$pass)
  300 = MySQL > v4.1
  900 = MD4
 1000 = NTLM
 1100 = Domain Cached Credentials
 1400 = SHA256

Default Values

Attribute Value Note
--version false
--help false
--eula false
--quiet false
--outfile NULL
--outfile-format 0
--remove false
--salt-file NULL
--runtime 0
--hex-salt false
--hex-charset false
--gpu-async false
--gpu-devices NULL
--gpu-accel 0
--gpu-loops 128
--gpu-watchdog 90
--custom-charset1 NULL
--custom-charset2 NULL
--custom-charset3 NULL
--custom-charset4 NULL
--increment false
--rule-left :
--rule-right :
--hash-type 0

NOTE: A value “0” or “NULL” can mean undefined, unlimited or all.

Supported algorithms and supported password plaintext lengths

Hash-Type minimum length maximum length Note
MD5 2 15
md5($pass.$salt) 2 15 1
md5($salt.$pass) 2 15 1
md5(md5($pass)) 2 15
vBulletin < v3.8.5 2 15
SHA1 2 15
sha1($pass.$salt) 2 15 1
sha1($salt.$pass) 2 15 1
MySQL > v4.1 2 15
MD4 2 15
NTLM 2 14 3
Domain Cached Credentials 2 14 3, 2
SHA256 2 15
  • 1 Indicates that the maximum length for salt is 31.
  • 2 Indicates that the maximum length for salt is 15.
  • 3 Indicates that the maximum length for password (per side) is 7.

Supported attack modes, direct


Please use the reference at homepage to get latest benchmarks.


  • There are no “rule-files” possible since the rules are applied in the loading-phase. Only one rule per side.
  • Rules can not apply on masks.

Future Plans

  • None
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