Re: [P1619-2] Subtle error/ambiguity in EME-2 drawing
I'm not going to be able to attend today but the fixed drawing looks OK to me -
Hal Finney
PGP Corporation
On Mon, Jan 25, 2010 at 10:11 AM, Fabio Maino <fmaino@xxxxxxxxx> wrote:
> Attached is the updated pic for discussion later today. This should address
> the issue pointed out by Colin.
> It's also in
> https://siswg.net/index.php?option=com_docman&task=doc_download&gid=217&Itemid=41
>
> Thanks,
> Fabio
>
> On 1/20/10 7:01 AM, Matt Ball wrote:
>
> Let's briefly discuss at the SISWG face-to-face meeting this Monday. I'll
> add it to the agenda.
>
> Cheers,
> -Matt
>
> On Mon, Jan 18, 2010 at 8:02 AM, Shai Halevi <shaih@xxxxxxxxxxxx> wrote:
>>
>> I concur, the summation should start at i=2. -- Shai
>>
>> Colin Sinclair wrote:
>> > Folks,
>> >
>> > I just noticed a subtle but minor error/ambiguity on the EME-2 drawing
>> > (Figure 2) in the 1619-2 drafts.
>> >
>> > It concerns the summations sum(PPP_j) and sum(CCC_j) which used to be
>> > called
>> > SP and SC respectively in the original EME (EME-32-AES-Nov-04.pdf). When
>> > Shai updated this to EME-2 by back in 2007, these intermediate variables
>> > and
>> > the precise definition of the summation were dropped and this is when
>> > the
>> > drawing became wrong, or at least ambiguous. Compare the pseudocode in
>> > Tables 3 & 4 which correctly says:
>> >
>> > MP = PPP_1 ^ PPP_2 ^ ... ^ PPP_m ^ T_star
>> > and CCC_1 = MC ^ CCC_2 ^ ... ^ CCC_m ^ T_star
>> >
>> > with the drawing which shows:
>> >
>> > MP = PPP_1 ^ sum(PPP_i) ^ T_star
>> > and CCC_1 = MC ^ sum(CCC_i) ^ T_star
>> >
>> > Unless the bounds of the summation on the drawing are explicitly stated
>> > as
>> > i=2..m, then the PPP_1 term will cancel and block 1 will be lost!
>> > Similarly
>> > on the ciphertext side.
>> >
>> > Sorry I didn't get this to you in time for last week's meeting, I only
>> > spotted it on the day of the meeting when scanning the latest draft.
>> >
>> > Regards,
>> > Colin.
>> >
>> > Colin Sinclair
>> > HELION Technology Limited
>> > Ash House, Breckenwood Road
>> > Fulbourn, Cambridge CB21 5DQ
>> > England.
>> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> > tel: +44 1223 500 924
>> > fax: +44 1223 500 923
>> > http://www.heliontech.com
>> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> >
>
>
>
> --
> Thanks!
>
> Matt Ball, Chair, IEEE P1619 Security in Storage Working Group
> Staff Engineer, Sun Microsystems, Inc.
> 500 Eldorado Blvd, Bldg #5 BRM05-212, Broomfield, CO 80021
> Work: 303-272-7580, Cell: 303-717-2717
>
>