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Date: Tue, 5 May 2015 22:53:10 +0300
From: Aleksey Cherepanov <lyosha@...nwall.com>
To: john-dev@...ts.openwall.com
Subject: Re: get_binary_*() and get_hash_*() methods
On Tue, May 05, 2015 at 09:07:49PM +0200, Frank Dittrich wrote:
> On 05/05/2015 08:53 PM, Aleksey Cherepanov wrote:
> > Formats provide get_binary_[0-6]() and get_hash_[0-6]() methods to
> > john. If the algo in them is the same then it is possible to construct
> > default cmp_all function. Are they used this way? Are they required to
> > have the same algo? If so, why is not there default cmp_all() based on
> > them?
>
> I think many formats could just use fmt_default_binary_hash_0 -
> fmt_default_binary_hash_6. Only formats which know that their hashes
> have a non-random distribution in (certain parts of) their hashes should
> need to implement their own binary_hash_[0-6].
> But I think fmt_default_binary_hash_0 - fmt_default_binary_hash_6 are
> jumbo specific, they don't exist in core.
>
> But fmt_default_salt_hash just returns 0 (which is OK for saltless hashes).
> So, we would need other "default" implementations for salt_hash_[0-6].
I don't touch salt_hash() yet.
I mean, we can implement cmp_all using other methods, something like
the following:
static int cmp_all(void *binary, int count)
{
int i;
int b = fmt_default_binary_hash_6(binary);
for (i = 0; i < count; i++) {
if (get_hash_6(i) == b)
return 1;
}
return 0;
}
Though some formats define get_hash_6 as "return 0;".
Hm, get_hash_6 is in format's file. self is needed to access it in
default implementation. But then it will not be inlined.
A macro may be used to insert the code of cmp_all into format's file.
Though get_hash_6 gives only 31 bits, while raw-sha512 checks all 64
bits in 1 check.
So I think my question about default implementation of cmp_all is
solved.
Does binary_hash_6() and get_hash_6() functions have to return the
same values for the same hashes?
Thanks!
--
Regards,
Aleksey Cherepanov
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