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Date: Tue, 5 May 2015 22:53:10 +0300
From: Aleksey Cherepanov <>
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

Does binary_hash_6() and get_hash_6() functions have to return the
same values for the same hashes?


Aleksey Cherepanov

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