offline keygeneration

Prasad ndprasad at gmail.com
Tue Oct 3 02:00:12 WST 2006


Hans,
I printed the size of the alloc after the mp_exptmod_fast() function
was called and it was changing from 0x40 to 0xC0. So this is what i
did in my keyread function(which reads from the file all the fields of
mp_int ) after i allocate the memory. This seems to solve the problem.

 if (dh_pub->alloc != MP_PREC)
   {
        m_free (dh_pub->dp);
        dh_pub->dp = m_malloc (sizeof (mp_int) * dh_pub->alloc);
        TRACE (("pub key Alloc size changed\n"));
   }

> On 10/2/06, Hans-Christian Egtvedt <hcegtvedt at atmel.com> wrote:
> > >
> > > Turns out underlying libtommath exp function changes/reallocates the
> > > value of alloc and dp (in the mp_int) from whatever allocated in
> > > mp_init(). This was the problem that was causing me weird behaviour
> > > (becos of uclinux). Now offline keygeneration works fine for me.
> >
> > This is interessting, where in the code did you discover this? This
> > might be the root to some problems I see on my platform.
> >
> > --
> > With kind regards,
> > Med vennlig hilsen,
> >
> > Hans-Christian Egtvedt, siv.ing. (M.Sc.)
> > Applications Engineer - AVR Applications Lab
> > Atmel Norway
> >
>



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