From: Bill Frantz <frantz@pwpconsult.com>
Replying To: Rob Withers <rwithers12@attbi.com>
Date: Wed, 20 Nov 2002 11:14:31 -0800
Subject: Re: [e-lang] [VatTP] MAC calculation

At 10:44 PM -0800 11/19/02, Rob Withers wrote:
>    Never mind these questions, folks, I managed to  find the issue.  CBC
>was broken and so I disabled it.  I am feeding  the padded plaintext, on
>the Receive side, to the computeMac: method.  I  see that I need to go
>ahead and unmarshall the aggregated msgs, to remove the  pad.  The part
>that makes me shudder is recalculating each msg header for  feeding the
>SHA1 hash function.  Other than this it is working.    :)   rob

The basic reasoning is to include as much of the hairy communication code
under the MAC,  so the MAC can test for edge cases that aren't handled
properly.  We actually found a bug in the old E protocol that resulted in a
one bit difference in the MAC.

If we include compression in some future version of the protocol, having
the MAC check the compression/expansion seems to me to be a useful feature. 

What was the bug you found in CBC?  I will need to fix it. 

Cheers - Bill 


-------------------------------------------------------------------------
Bill Frantz           | The principal effect of| Periwinkle -- Consulting
(408)356-8506         | DMCA/SDMI is to prevent| 16345 Englewood Ave.
frantz@pwpconsult.com | fair use.              | Los Gatos, CA 95032, USA


_______________________________________________
e-lang mailing list
e-lang@mail.eros-os.org
http://www.eros-os.org/mailman/listinfo/e-lang