search

openwall / john

John the Ripper jumbo - advanced offline password cracker, which supports hundreds of hash and cipher types, and runs on many operating systems, CPUs, GPUs, and even some FPGAs
https://www.openwall.com/john/
Other
10.4k stars 2.11k forks source link

We lack developer documentation #1475

Open frank-dittrich opened 9 years ago

frank-dittrich commented 9 years ago

What we need to document:

(And I am sure lots of other stuff)

magnumripper commented 9 years ago
magnumripper commented 9 years ago

Openwall's wiki is almost dead and that might be partly because it's horrible to use: It's the worst wiki [the software] I've encountered as a writer.

On the other hand, this Github wiki is, in my opinion, wonderful. It's simple and intuitive. I have some pages here mostly for my own notes.

jfoug commented 9 years ago

https://github.com/magnumripper/JohnTheRipper/wiki/Developer-Help-Documentation

I have added some place holder pages, listing all items from this post. I really would like to be able to control what shows up in that 'Pages' sidebar. It will get HEAVILY cluttered and unusable.

magnumripper commented 9 years ago

The place holders are annoying. Please either drop them for now, or fill them in.

frank-dittrich commented 9 years ago

Another question: How to decide whether or not an OpenCL format should be OMP or not. E.g., rar-opencl is OMP, some other formats are OMP as well, but (at least for my Haswell with beignet) I don't really know why.

magnumripper commented 9 years ago

It's pretty obvious: For example, the CUDA version of WPAPSK does significant post-processing on CPU, so should (and does AFAIK) use OpenMP for that. The OpenCL version does it all on GPU, so there's simply nowhere you could put an OpenMP pragma.

frank-dittrich commented 9 years ago

OK, then I might need a real GPU instead of Intel's Haswell to see the benefit of using OpenMP for rar-opencl. For me. there's no difference running a non-OMP version, and the CPU is still mostly idle.

magnumripper commented 9 years ago

You got it backwards. Again, the OpenCL version of WPA does not and can not utilize OpenMP, because all work is done on GPU.

frank-dittrich commented 9 years ago

NO, I didn't get it backwards. I didn't mention WPA at all. I just discussed rar-opencl. May be here the CPU has work to do, but at least with my Haswell, there's so little work to do for the CPU that the CPU is idle most of the time, even in a --disable-openmp build.

magnumripper commented 9 years ago

Oh, my bad. The thing with RAR is we have very good early rejection nowadays. Whenever that code fails to reject early, we need to do, worst case, an AES decryption of a whole file in the archive. That file is potentially huge.

frank-dittrich commented 9 years ago

Can that AES decryption of a whole file benefit from OpenCL? I just ask because I intend to run rar-opencl in parallel ro rar (where I would use default OMP_NUM_THREADS on CPU), and I am afraid that enabling OpenCL for GPU might hurt perfrmance rather than help.

frank-dittrich commented 9 years ago

The --test benchmarks just indicate that I can combine --format=rar and --format=rar-opencl, and get more or less the same speeds as when I run --format=rar and --format=rar-opencl individually.

magnumripper commented 9 years ago

AES can be done on GPU but I don't think it's worth it. But I'm pretty sure it will be worthwhile to run CPU and GPU in parallel, because of the mentioned early rejection stuff.

magnumripper commented 9 years ago

We should also document the use of error() and pexit(). And why to use them (there are very good reasons) instead of exit() when possible.

magnumripper commented 9 years ago

Some stuff in #350 too.

kholia commented 7 years ago

We also have a doc/HACKING.md file now. I am looking for suggestions about topics which could be added to this file.