Date: Fri, 14 Jun 2019 13:58:33 +0200 From: Solar Designer <solar@...nwall.com> To: john-users@...ts.openwall.com Subject: Re: Issues cracking an ssh key On Mon, Jun 10, 2019 at 07:25:14PM +0530, Dhiru Kholia wrote: > On Fri, May 31, 2019 at 10:17 PM Adam Lininger <arlininger@...il.com> wrote: > > I've got an encrypted ssh private key. I've managed to use ssh2john to > > convert it and seem to have a crack (using --format=ssh-opencl). > > However, the resulting passphrase doesn't decrypt the key. Instead > > openssl errors out. > > > > When I use --format=ssh and a fresh pot file, the same passphrase does > > NOT appear to crack the key. What's odd is that the ssh format warns > > about false positives and keeps going while ssh-opencl does not. > > The OpenCL SSH code is missing the "second round" (extra set) of > verification checks IIRC, which leads to this problem of false > positives. I am not sure how hard it would be to make the OpenCL SSH > code as rigorous as the CPU code (I haven't seen JtR code in a while). Meanwhile, we've just added the FMT_NOT_EXACT flag to ssh-opencl in bleeding-jumbo, which will make it keep going after finding a guess. The same effect can also be achieved using the "--keep-guessing" option. Alexander
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