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Date: Sun, 18 Dec 2011 06:38:13 +0530
From: piyush mittal <piyush.cse29@...il.com>
To: john-dev@...ts.openwall.com
Subject: Re: Bit slice implementation of DES based hashes

>
> You really don't need salts and iterations of DES_bs_crypt().  You need
> different ones, which you may implement externally to your slight
> revision of DES_bs_crypt_LM().
>

Yes *Of course.*May be today I will be able to finish out the whole work*.*


Thanks




On Sun, Dec 18, 2011 at 3:54 AM, Solar Designer <solar@...nwall.com> wrote:

> On Sat, Dec 17, 2011 at 10:01:24PM +0530, piyush mittal wrote:
> > Yes, that is true that we can call  DES_bs_set_key() with same fixed key
> > for all layers.But what about different plain text that we need i.e if we
> > see into struct fmt_main initialisation it sends all stored list of
> > password through method set_key().
>
> Just because the format method is named set_key() doesn't imply that it
> has to call DES_bs_set_key().  In your case, it sounds like it should not.
> Instead, according to what you're saying, it should either initialize a
> bit layer in B or it should save the password as-is e.g. in a
> saved_key[] entry (like some formats do) and then have crypt_all()
> process those passwords into their bit layers in B[] before calling a
> revision of DES_bs_crypt_LM().
>
> > > As I suggested, DES_bs_crypt_LM() is a closer match.  DES_bs_crypt()
> > > adds salts and iterations, which you don't need.
> >
> > No.Salt and iterations also exist in oracle.Salt here is user name and we
> > need two iterations.
>
> You really don't need salts and iterations of DES_bs_crypt().  You need
> different ones, which you may implement externally to your slight
> revision of DES_bs_crypt_LM().
>
> > Let me summarise you what actually going on.
> >
> > 1.Concatenate user name(i.e salt) and password to get plain text
> string(i.e
> > input plain text for DES).
> > 2.Encrypt plain text string in CBC mode using fixed key
> 0x0123456789ABCDEF.
> > 3.Encrypt the plain text string again in CBC mode but using the last
> block
> > of o/p of previous step as the encryption key.
> >
> > so if I will apply DES_bs_crypt_LM() then step 2 can be done but step 3
> > again needs number of modifications
>
> Please don't worry about efficiency for your initial implementation.
> When you don't worry about efficiency, you can just use a trivial
> revision of DES_bs_crypt_LM() (with B initialization removed) for both
> step 2 and step 3 above.  You will need to replace K between steps 2 and
> 3, but you can do it externally to the function.
>
> Of course, the goal of bitslicing is to improve performance, so you will
> need to worry about it at some point, but initially your goal is just to
> get things working.
>
> Thanks,
>
> Alexander
>



-- 
Piyush Mittal
Department of Computer Science and Engineering
National Institute of Technology,Rourkela
INDIA

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