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Date:      Thu, 4 May 2000 13:20:12 -0500 (EST)
From:      "Andrew J. Korty" <ajk@iu.edu>
To:        Mark Murray <mark@grondar.za>
Cc:        Matthew Dillon <dillon@apollo.backplane.com>, security@FreeBSD.ORG
Subject:   Re: Cryptographic dump(8) 
Message-ID:  <Pine.BSF.4.21.0005041318270.26492-100000@verbal.uits.iupui.edu>
In-Reply-To: <200005040628.IAA05648@grimreaper.grondar.za>

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> >     Store something like this in the header:
> 
> [ Good stuff snipped. ]
> 
> >     Storing a random sequence in the header that is MD5'd as well as 
> >     encrypted is very important because otherwise someone trying to break
> >     the encryption can 'guess' at what the contents of the header was in
> >     order to try to reverse-engineer the encryption.
> 
> Yes! It is _very_ important that the random number is cryptographically
> secure, ant that it is first, so as to maximise the security of the block
> cipher. It is also important to use one of the "feedback" modes, to spread
> the entropy over the whole block, seeing that this block is of paramount
> importance.

I was under the impression that the CBC mode would also propagate this
entry throughout the block.  Must I use one of the feedback modes?
-- 
Andrew J. Korty, Lead Security Engineer
Office of the Vice President for Information Technology
Indiana University



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