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Date: Wed, 27 Apr 2011 05:25:12 +0400
From: Solar Designer <>
Subject: Re: Bcrypt functionalities implementation in hardware

On Tue, Apr 26, 2011 at 04:50:03PM -0300, Yuri Gonzaga wrote:
> Alexander talked about implementing only the inner loop of bcrypt or the
> 2^cost loop.

It should be the latter.

> (From
> )
> bcrypt(cost, salt, key)
> >    state <- EksBlowfishSetup(cost, salt, key)
> >    ctext <- "OrpheanBeholderScryDoubt"
> > *   repeat(64)
> > **      ctext <- EncryptECB(state, ctext)
> > *   return Concatenate(cost, salt, ctext)
> Is this (in bold) the inner loop?

No.  This is a cheap loop that may be implemented in software.  The one
we need to implement in hardware is in EksBlowfishSetup().

> (From
> )
> EksBlowfishSetup(cost, salt, key)
> >    state <- InitState()
> >    state <- ExpandKey(state, salt, key)
> >  *  repeat(2^cost)
> > **      state <- ExpandKey(state, 0, salt)
> > **      state <- ExpandKey(state, 0, key)
> > *   return state
> Is this the other one?

Yes, this is the only one to implement in hardware.

I am sorry that I confusingly used different words in the IM
conversation we had.  I only meant one loop.

> So, Should the other pieces of code implemented in software?

Yes, provided that sending a little over 4 KB of data to/from FPGA is no
problem - e.g., it might be problematic over your JTAG/USB adapter
cable, but it should be no problem over USB 2.0 or PCIe.

Since we'll need interfacing from C code, I suggest that you pick my
crypt_blowfish package:

or JtR's BF_std.c (force it to the simpler BF_X2=0 and BF_mt=1 case) and
replace the loop with a call into the FPGA interface.  You don't need to
implement the rest of bcrypt in C on your own - the existing code should

In BF_std.c, the loop to replace is:

		count = salt[4];
		do {
		} while (--count);



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