From: "James A. Donald" <jamesd@echeque.com>
Date: Thu, 25 Jan 1996 15:58:26 +0800
To: cypherpunks@toad.com
Subject: Re: Why is blowfish so slow?  Other fast algorithms?
Message-ID: <199601250629.WAA16623@mailx.best.com>
MIME-Version: 1.0
Content-Type: text/plain


At 07:32 PM 1/23/96 -0500, David A Wagner wrote:

>If you want authentication, you must use a crypto-strength MAC.
>Encryption (be it RC4, DES, etc.) is not enough.

Not so:  If the message is encrypted and checksummed with a simple
not non cryptographic checksum, this gives you everything a MAC 
gives you, plus the message is secret.

MACs are only useful in the strange and unsual case where you want
authentification using a symmetric key, but you want to transmit in
the clear.  I cannot see any reason why anyone would ever wish to use
a MAC except perhaps to obey government bans on encrypted messages.

 ---------------------------------------------------------------------
              				|  
We have the right to defend ourselves	|   http://www.jim.com/jamesd/
and our property, because of the kind	|  
of animals that we are. True law	|   James A. Donald
derives from this right, not from the	|  
arbitrary power of the state.		|   jamesd@echeque.com