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Re: determining the initialization vector in CBC mode

To: Peadar Harmon <peadar@nortelnetworks.com>
Subject: Re: determining the initialization vector in CBC mode
From: obennis@motus.qc.ca
Date: Thu, 21 Oct 1999 15:08:03 -0400
cc: ipsec@lists.tislabs.com
Sender: owner-ipsec@lists.tislabs.com

Hi,

In order to compute the IV, you don't need a HMAC hash function like HMAC-MD5
but a Hash function like MD5, SHA or Tiger as illustrarted in the RFC- 2409 page
33.
A Hash function doesn't use a key to compute a Hash value. The HMAC functions do
need a key to compute a specific hash wich can be used for integrity check and
authentication.

So IV = prf(  g^xi | g^xr)  and prf is MD5, SHA-1 or Tiger

Omar Bennis
Motus Technologies Inc

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