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Date: Tue, 1 Jan 2013 21:12:58 +0100
From: magnum <john.magnum@...hmail.com>
To: john-dev@...ts.openwall.com
Subject: Re: A few questions regarding the newly added BLAKE2 format

On 1 Jan, 2013, at 20:22 , Dhiru Kholia <dhiru.kholia@...il.com> wrote:
> On Wednesday 02 January 2013 12:37 AM, Frank Dittrich wrote:
>> Should we really allow newly added formats to treat ambiguous hashes as
>> valid?
>> The hash
>> 4245af08b46fbb290222ab8a68613621d92ce78577152d712467742417ebc1153668f1c9e1ec1e152a32a9c242dc686d175e087906377f0c483c5be2cb68953e
>> is considered as valid by raw-sha512 and more than 20 dynamic formats.
>>  
> 
> I don't like "raw" hashes (hashes without leading FORMAT_TAG) much. If magnum agrees, I can remove support for them
> from BLAKE2 format.



First let's ignore dynamic:

My personal opinion is that we should definitely accept untagged hashes, of course provided that the length and charset is correct. We have this very good feature where John tells us what formats could be using the hash. To make an input file automatically pick a certain format, add tags in the file with a trivial sed one-liner. Or just supply the --format option. On a related note, I think we should always add tags to john.pot (and this format do) unless the hash format is odd enough to be easily recognized even with future in mind. I'd really like to hear other's opinions too, including but not limited to Solar. And the john-users crowd too btw.

Second, the dynamic format currently does not seem to accept *any* untagged hash until you set DynamicAlwaysUseRawHashes=Y in john.conf. But if you do, dynamic seem to get too greedy, even accepting this 128 character hash as raw-md5! I am not quite sure how it is supposed to work: Maybe the current behavior is on purpose and it would only use the first 32 characters of that 128 char hash for eg. raw-md5? If that's it, I would prefer dynamic to accept it as dynamic_80 with that option turned off. But that is up to Jim to decide, I know dynamic is very complicated.

magnum

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