From: David Mazieres <dm@amsterdam.lcs.mit.edu>
Date: Mon, 22 Jan 96 10:51:25 PST
To: "James A. Donald" <jamesd@echeque.com>
Subject: Re: Why is blowfish so slow?  Other fast algorithms?
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Message-ID: <199601221851.NAA16938@amsterdam.lcs.mit.edu>
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In article <199601221601.IAA14610@mailx.best.com> "James A. Donald" <jamesd@echeque.com> writes:

> From: "James A. Donald" <jamesd@echeque.com>
> Date: Mon, 22 Jan 1996 19:56:43 -0800
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> At 02:00 AM 1/22/96 -0500, David Mazieres wrote:
> >Failing that, can anyone suggest other secure, preferably unpatented,
> >shared-key encryption algorithms that could encrypt at ethernet speeds
> >(1 MByte/sec) without using most of the CPU on a fast Pentium or
> >equivalent processor?
> 
> RC4 is of course unpatented and faster than anything else.
> Of course the name RC4 is trademarked, so you could simply 
> call it "the well known algorithm" in your documentation 
> and give the algorithm explicitly.

The problem with RC4 is that it works in OFB only.  If I need data
integrity in the face of known plaintext, I will need to compute a MAC
in paralell with the encryption which could significantly slow things
down.  With a block cypher in CFB, I can just re-encrypt the last
block of data.

That said, OFB has the advantage that I can overlap computation of the
RC4 stream with I/O, which might be a win for me.  Are there any MACs
significantly faster than say ~50 cycles per byte?

Thanks,
David