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

Header Data

From: nospam-seesignature@ceddec.com
To: Ray Arachelian <sunder@brainlink.com>
Message Hash: f0d7a74292b2a8791691d2b99a1f0703c2ba51dc34866f8a383b2626787ca7a1
Message ID: <97Aug13.172635edt.32257@brickwall.ceddec.com>
Reply To: <Pine.SUN.3.96.970813145505.7599M-100000@beast.brainlink.com>
UTC Datetime: 1997-08-13 21:36:30 UTC
Raw Date: Thu, 14 Aug 1997 05:36:30 +0800

Raw message

From: nospam-seesignature@ceddec.com
Date: Thu, 14 Aug 1997 05:36:30 +0800
To: Ray Arachelian <sunder@brainlink.com>
Subject: Re: Encrypting same data with many keys...
In-Reply-To: <Pine.SUN.3.96.970813145505.7599M-100000@beast.brainlink.com>
Message-ID: <97Aug13.172635edt.32257@brickwall.ceddec.com>
MIME-Version: 1.0
Content-Type: text/plain



On Wed, 13 Aug 1997, Ray Arachelian wrote:

> On Wed, 13 Aug 1997 nospam-seesignature@ceddec.com wrote:
> 
> In terms of padding does it matter WHERE I put the padding info?  Is it
> better to put random stuff in the front or at the end?  The reason I ask,
> say that you're going to encrypt an N byte block where N is bigger than
> your block cypher's key size?
> 
> If my intution is correct, and you have the same data encrypted with many
> keys (even RSA) but have the padding at the end, the 1st block would still
> be breakable.  I suppose putting the data at the end would also result in
> the same kind of problem, though it might be a bit harder to attack than
> putting the data 1st...
> 
> Would it not make sense to scatter the random padding throughout the
> block?   How is this normally done?  Front?  Back?  Middle?  Scattered?

The location does not matter.  The standard RSA libs place the padding at
the front - it is one of those PKCS specifications.

You would simply need to break the conventional key down to a few bytes
smaller than the modulus size, so each would be padded with a few random
bytes.

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