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Date: Sat, 15 Sep 2018 10:04:28 -0300
From: Claudio André <>
Subject: John the Ripper on Windows (includes OpenCL on Windows)

Hi all, after a private discussion about JtR on Windows I would like to 
share my point of view [1].

I would say that if you need John for Windows you should use [2][3]:
- it is 100% JtR magnum's source code;
- it is built and tested on an actual (and auditable) Windows machine;
- it works on CMD, no need to install CygWin, ...
- I (tried, at least, to) handled all details;

For example: from jeff at
 > Warning: '/dev/shm' does not exists or is not a directory.
 > POSIX shared memory objects require the existance of this directory.
 > Create the directory '/dev/shm' and set the permissions to 01777.
 > For instance on the command line: mkdir -m 01777 /dev/shm
 > No OpenCL devices found

This is a known issue, please read:

Well, my advice is (and it applies to all "Windows situations"):
- use the package ( and check if it works;
- or verify if replacing cygOpenCL-1.dll with OpenCL.dll JtR works;
- or what happens if other format is used;

What I know:
- CygWin OpenCL DLL needs proper ICD information;
- This information might be in some package I'm not aware (yet). I need 
to play with CygWin when I put my hands on some M$ box.
- I doubt you have all the necessary things in the right place.
- Anyway, IMO, the choices made by CygWin make sense;

That said, I know the package works "out of the box" for some people. 
Still need to test it in the wild.


[1] I'm not a mailing list user [4]. So, I'm afraid I can't be part of 
the discussions.
[2] The readme is at
[3] At least,
      - check if you are running an updated CygWin
      - check if you have installed all needed CygWin OpenCL packages
      -  run `strace -e -f trace=open john [arguments]`
      And so on.
[4] They are pre-flood tech, IMO.

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