1994-09-14 - Re: alleged-RC4

Header Data

From: Bill Sommerfeld <sommerfeld@orchard.medford.ma.us>
To: Hal <hfinney@shell.portal.com>
Message Hash: d0f8fb7b2adc73244ae7b02894c86ed17f67d8a4b6597c369cf11ede38f868c0
Message ID: <199409141522.LAA00525@orchard.medford.ma.us>
Reply To: <199409140402.VAA26572@jobe.shell.portal.com>
UTC Datetime: 1994-09-14 15:36:57 UTC
Raw Date: Wed, 14 Sep 94 08:36:57 PDT

Raw message

From: Bill Sommerfeld <sommerfeld@orchard.medford.ma.us>
Date: Wed, 14 Sep 94 08:36:57 PDT
To: Hal <hfinney@shell.portal.com>
Subject: Re: alleged-RC4
In-Reply-To: <199409140402.VAA26572@jobe.shell.portal.com>
Message-ID: <199409141522.LAA00525@orchard.medford.ma.us>
MIME-Version: 1.0
Content-Type: text/plain


I agree; this cypher should definitely be handed a unique key each
time it is used.

However, you can do this pretty easily for file encryption, too..
Generate and store an "initialization vector" with each file of
cyphertext.  Instead of passing the user key directly to RC4, you
instead pass a hash (MD5 or SHA) of the user key concatenated with the
IV.

If you don't have room to store the IV's, you could use some
position-dependant information (e.g., per disk ID plus disk block
number or file inode number) instead.

						- Bill

Thread

• Return to September 1994

• Return to “Bill Sommerfeld <sommerfeld@orchard.medford.ma.us>”
• Return to “Hal <hfinney@shell.portal.com>”

• Return to “schneier@chinet.chinet.com (Bruce Schneier)”

• 1994-09-13 (Mon, 12 Sep 94 21:18:26 PDT) - RC4 - schneier@chinet.chinet.com (Bruce Schneier)
  • 1994-09-13 (Mon, 12 Sep 94 23:05:45 PDT) - Re: RC4 - Hal <hfinney@shell.portal.com>
    • 1994-09-13 (Tue, 13 Sep 94 08:13:32 PDT) - Re: alleged-RC4 - Bill Sommerfeld <sommerfeld@orchard.medford.ma.us>
      • 1994-09-14 (Tue, 13 Sep 94 21:02:52 PDT) - Re: alleged-RC4 - Hal <hfinney@shell.portal.com>
        • 1994-09-14 (Wed, 14 Sep 94 08:36:57 PDT) - Re: alleged-RC4 - Bill Sommerfeld <sommerfeld@orchard.medford.ma.us>