1994-09-15 - thoughts on RC4

Header Data

From: perry@imsi.com (Perry E. Metzger)
To: cypherpunks@toad.com
Message Hash: 27ba39edcdada11b49cda45f7131af94abf3bca210407e7b7f323ba6466a7636
Message ID: <9409151452.AA03618@webster.imsi.com>
Reply To: N/A
UTC Datetime: 1994-09-15 14:52:27 UTC
Raw Date: Thu, 15 Sep 94 07:52:27 PDT

Raw message

From: perry@imsi.com (Perry E. Metzger)
Date: Thu, 15 Sep 94 07:52:27 PDT
To: cypherpunks@toad.com
Subject: thoughts on RC4
Message-ID: <9409151452.AA03618@webster.imsi.com>
MIME-Version: 1.0
Content-Type: text/plain

I've been looking at the RC4 (or alleged RC4) code a bit.

Unlike most ciphers, RC4 doesn't seem to have any particular word
length dependancies in its principles. That is to say, a cipher like
IDEA has lots of magic numbers involved, but RC4 does not, which means
that one could, in principle, extend it from being byte oriented
stream to being word oriented stream without causing particular
harm. (It would, of course, become incompatible, but thats not a real
issue.) Can anyone see any reason why one could not change RC4 to
being a word oriented stream cipher, call it "ERC4"?

The reason I ask is because this would speed things up by a factor of
four on 32 bit machines, which would mean modest hardware could
possibly break 100mbps speeds. The 64 bit extension on 64 bit RISC
processors could go far, far, faster still.

This is a real consideration in the protection of network traffic,
where extremely fast encryption in software has been a stumbling block.