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1997-08-13 - Re: Encrypting same data with many keys…

Header Data

From: Bill Stewart <stewarts@ix.netcom.com>
To: amp@pobox.com
Message Hash: bb275df0a9e1749ab54428748db90816213f1a43272751edba0d6309f21e7021
Message ID: <3.0.2.32.19970813003535.0068e9b4@popd.ix.netcom.com>
Reply To: <Pine.SUN.3.96.970812111223.26326D-100000@beast.brainlink.com>
UTC Datetime: 1997-08-13 07:46:38 UTC
Raw Date: Wed, 13 Aug 1997 15:46:38 +0800

Raw message

From: Bill Stewart <stewarts@ix.netcom.com>
Date: Wed, 13 Aug 1997 15:46:38 +0800
To: amp@pobox.com
Subject: Re: Encrypting same data with many keys...
In-Reply-To: <Pine.SUN.3.96.970812111223.26326D-100000@beast.brainlink.com>
Message-ID: <3.0.2.32.19970813003535.0068e9b4@popd.ix.netcom.com>
MIME-Version: 1.0
Content-Type: text/plain



At 05:37 PM 8/12/97 -0500, amp@pobox.com wrote:
>So would that then be a possible weakness in encrypting to multiple 
>recipients with PGP? Probably not, since the actual data is encrypted with 
>idea.

The actual data is encrypted with IDEA, but the identical IDEA key is 
encrypted with each recipient's RSA key.  To avoid this attack,
PGP uses random padding after the IDEA key (which makes the message
encrypted with RSA different for each recipient, avoiding the trap.
Since IDEA keys are 128 bits long, and RSA moduli are typically 384-2047,
there's plenty of room for random noise in the format.)


#			Thanks;  Bill
# Bill Stewart, +1-415-442-2215 stewarts@ix.netcom.com
# You can get PGP outside the US at ftp.ox.ac.uk/pub/crypto/pgp
#   (If this is a mailing list or news, please Cc: me on replies.  Thanks.)

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