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Date: Mon, 17 Dec 2012 00:09:13 +0100
Subject: Re: gpg2john -> false positive -> how to exclude?

Hi magnum,

thanks for your fast and detailed answer, that helps in understanding 
how it works.
Supplying the key would be no real problem since - as you guessed 
correctly - this key is in no
productive use anymore.
Here some facts about my setup: 'make linux-x86-64-native', enabled the 
two "gcc with openMP" lines in the Makefile.

the converted gpg2john hash is:

the one false positive i got is in clear-text: bortaloo
(which is not my phrase | and thus does not work for unlocking)

output of gpg --list-secret-keys is:
sec   1024D/615B53E0 2001-01-29
uid                  Donny
ssb   1024g/8646A815 2001-01-29

john-version used: unstable-jumbo (from .git as zip-download via http)

If you need the real secring.pgp and a ciphertext file, private email 
would be great :)


On 16.12.2012 23:15, magnum wrote:
> On 16 Dec, 2012, at 21:04 , wrote:
>> is it possible to let john go on with brute-forcing in incremental mode, after
>> an obvious false positive is found?
> Some formats are expected to have collisions, like CRC32 for instance. You can make any format behave like such by adding FMT_NOT_EXACT to the format flags in the end (normally) of the source file. In this case, this line:
> of gpg_fmt_plug.c (or opencl_gpg_fmt.c) would be
> However, see below.
>> I recently did 'gpg2john' and finally ended up with incremental mode and got an false positive.
>> I forgot my gpg-passphrase (from>10 years ago), and I know it's not the found word, besides:
>> it simply does not work :)
> As far as I understand from the source, it should really not emit false positives. Maybe there is a bug in the format. At worst that means once Dhiru fixes it you'd have to re-start from scratch.
> We might need more information. Were you running the CPU format or the OpenCL one? And are you using Jumbo-7 or the unstable-jumbo from git? Would you by any chance reveal the gpg key or input file (perhaps privately, to Dhiru) so we can reproduce the bug? I take it you do not use that passphrase anymore anyway :)  Failing that, I guess we'd be helped by knowing what exact time key it is.
> magnum

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