1994-09-17 - Re: if this is RC4

Header Data

From: Jim Gillogly <jim@acm.org>
To: cypherpunks@toad.com
Message Hash: 60f7a78a659250c53db263f0ab17e716985256fcbd1e94550ba9a1f3c6748853
Message ID: <9409171644.AA08193@mycroft.rand.org>
Reply To: <9409171312.AA24429@prism.poly.edu>
UTC Datetime: 1994-09-17 16:44:38 UTC
Raw Date: Sat, 17 Sep 94 09:44:38 PDT

Raw message

From: Jim Gillogly <jim@acm.org>
Date: Sat, 17 Sep 94 09:44:38 PDT
To: cypherpunks@toad.com
Subject: Re: if this is RC4
In-Reply-To: <9409171312.AA24429@prism.poly.edu>
Message-ID: <9409171644.AA08193@mycroft.rand.org>
MIME-Version: 1.0
Content-Type: text/plain



> rarachel@prism.poly.edu (Arsen Ray Arachelian) writes:
> > One possibility is that the author may have simply decompiled the
> > original code...

> This might explain the char % 255's in the code.  Normally such a 
...
> may surprise some of us that some machines can do a MOD faster than
> an AND and the compiler used might have exploited that feature.

It wouldn't explain the construct Hal pointed out, though:

>         xorIndex = state[x] + (state[y]) % 256;

Here it's either a bug or a no-op, so a decompiler wouldn't have produced it.

	Jim Gillogly
	26 Halimath S.R. 1994, 16:43

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• 1994-09-15 (Thu, 15 Sep 94 11:59:51 PDT) - if this is RC4 - Carl Ellison <cme@tis.com>
  • 1994-09-15 (Thu, 15 Sep 94 12:06:52 PDT) - Re: if this is RC4 - “Perry E. Metzger” <perry@imsi.com>
    • 1994-09-16 (Thu, 15 Sep 94 18:25:33 PDT) - Re: if this is RC4 - “Ian Farquhar” <ianf@wiley.sydney.sgi.com>
      • 1994-09-16 (Fri, 16 Sep 94 06:18:41 PDT) - Re: if this is RC4 - “Perry E. Metzger” <perry@imsi.com>
        • 1994-09-16 (Fri, 16 Sep 94 07:55:18 PDT) - Re: if this is RC4 - jamesd@netcom.com (James A. Donald)
          • 1994-09-16 (Fri, 16 Sep 94 07:57:20 PDT) - Re: if this is RC4 - “Perry E. Metzger” <perry@imsi.com>
          • 1994-09-19 (Sun, 18 Sep 94 22:04:52 PDT) - Re: if this is RC4 - “Ian Farquhar” <ianf@wiley.sydney.sgi.com>
        • 1994-09-17 (Sat, 17 Sep 94 06:25:13 PDT) - Re: if this is RC4 - rarachel@prism.poly.edu (Arsen Ray Arachelian)
          • 1994-09-17 (Sat, 17 Sep 94 09:44:38 PDT) - Re: if this is RC4 - Jim Gillogly <jim@acm.org>