From: "Mark M." <markm@voicenet.com>
Date: Wed, 10 Jul 1996 08:09:43 +0800
To: cypherpunks@toad.com
Subject: Re: A case for 2560 bit keys
In-Reply-To: <199607090309.XAA00077@darius.cris.com>
Message-ID: <Pine.LNX.3.94.960709134510.248A-100000@gak>
MIME-Version: 1.0
Content-Type: text/plain


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On Mon, 8 Jul 1996, David F. Ogren wrote:

> Despite the above, there are convincing arguments for longer RSA keys.
> Instead of asking "Why should we have longer keys?", perhaps we should be
> asking "Why _shouldn't_ we have longer keys?"
> 
> In a hybrid cryptosystem such as PGP, very little of the computational
> process is consumed by RSA encryption.  Only a tiny fraction of the message
> is RSA encrypted (the session key), and thus the time-critical operation is
> the symmetric crypto system (IDEA for PGP).
> 
> As an experiment generate a 2047 bit PGP key and a 512 bit PGP key.
> Encrypt a file (preferably of a reasonable size) using both keys.
> Depending on the computer you are using, the time difference between the
> two keys will be a matter of few seconds or even a fraction of a second.

Now try decrypting the file, or signing another file.  I have a 486-66 which
is now considered hopelessly sluggish by today's standards.  It takes about
5 seconds, while doing the same operation with a 512-bit key takes less than a
second.  I sign every one of my messages, so such a time delay gets quite
annoying.  I do have a 2048-bit key and encourage people to encrypt messages
with it, but I won't be signing messages with that key anytime soon unless
there is a much faster mpilib for PGP.

Other than that, I do completely agree with what you have written.

- -- Mark

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