[47952] in Cypherpunks
Re: Why is blowfish so slow? Other fast algorithms?
daemon@ATHENA.MIT.EDU (James A. Donald)
Thu Jan 25 01:34:51 1996
Date: Wed, 24 Jan 1996 22:26:12 -0800
To: daw@beijing.CS.Berkeley.EDU (David A Wagner), cypherpunks@toad.com
From: "James A. Donald" <jamesd@echeque.com>
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.
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