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Date: Wed, 3 Oct 2012 18:45:09 +0200
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: o5logon format hacks
On 3 Oct, 2012, at 18:24 , magnum <john.magnum@...hmail.com> wrote:
> On 3 Oct, 2012, at 17:44 , Dhiru Kholia <dhiru.kholia@...il.com> wrote:
>
>> I have replaced the cracked array approach with standard get_hash* functions.
>>
>> But does this patch make any sense since binary value is always same?
>>
>> I suspect that it will still run into "too many collisions detected" problem.
>
> I think it does not make sense, it should probably be reverted (although there was some other changes too in that commit, right?). What you should do is use fmt_default_binary *and* set BINARY_SIZE to 0 for all formats that does not use a binary. This will change the warning text a little, as well as reduce unneeded memory use.
Maybe I'm confused now but here's how I *think* we could do to all non-hash formats in order to get proper dupe detection and no warnings.
1. Use a short binary size (eg. 4) so we don't waste too much memory.
2. Write a simple mockup binary() that just returns a 4-byte hash of the full ciphertext. This could be standard crc32 or something else, but it should use all of the ciphertext.
3. Use standard binary_hash() functions just like the ones you used now.
Actually, this binary() function will be 100% identical for all non-hash formats so I think the fmt_default_binary() should be modified to do this. BUT I'm not sure if any format actually use the present fmt_default_binary() as-is and depend on it's output (it currently outputs the ciphertext as-is). So we could instead name this new function (still in formats.c) fmt_default_binary_nonhash() or something like that.
BTW the binary_hash() functions too could be placed in formats.c as this would remove a lot of duplicated code.
magnum
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