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Date: Thu, 24 Jan 2013 19:18:48 +0100
From: Frank Dittrich <>
Subject: Re: Formats ssh and ssh-ng

On 01/24/2013 06:39 PM, magnum wrote:
> On 24 Jan, 2013, at 17:08 , Dhiru Kholia <> wrote:
>> On Thu, Jan 24, 2013 at 8:50 PM, Frank Dittrich
>> <> wrote:
>>> Can't ssh-ng report "SSH RSA / DSA" instead of "ssh-ng SSH RSA / DSA"?
>>> This would allow to pick the fastest of several benchmarks for
>>> performance comparison in relbench.
>>> (Of course, the format name should only be changed if both formats
>>> understand the same canonical hash representation and if ssh-ng doesn't
>>> produce false positives.)
>> ssh-ng *might* produce false positives (but it hasn't so far!) and
>> making ssh-ng understand old-style hashes requires more work (i.e.
>> patches welcome).
>> Hence, for now, it is better to treat them as separate formats.
> They should be separate formats in Jumbo, but I agree with Frank they could still be "one" format in relbench.

As long as ssh doesn't understand ssh-ng hashes and vice versa, there is
a risk of duplicate effort (cracking hashes which have already been
cracked using the other format).
If someone implements a prepare() for ssh-ng so that this format
understands the old ssh hash representation, we might want to move
up, so that it is registered before the plugin formats, *if* ssh-ng
really is still experimental.
That it can produce false positives is not that much of a problem,
provided the probability of false positives is very small.
(Did anybody compute that probability?)
Because of FMT_NOT_EXACT, john will not remove that hash once the first
match is found.
And you can still use --format=ssh to verify the password.


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