1994-07-26 - CYPHERPUNKS TO THE RESCUE

Header Data

From: hughes@ah.com (Eric Hughes)
To: cypherpunks@toad.com
Message Hash: 46e6a26eebc5e4a121785c23b53f572add8243be48ee211f06eb367131ecd38e
Message ID: <9407261649.AA05830@ah.com>
Reply To: <m0qSmuj-000I8XC@crynwr.com>
UTC Datetime: 1994-07-26 17:10:51 UTC
Raw Date: Tue, 26 Jul 94 10:10:51 PDT

Raw message

From: hughes@ah.com (Eric Hughes)
Date: Tue, 26 Jul 94 10:10:51 PDT
To: cypherpunks@toad.com
Subject: CYPHERPUNKS TO THE RESCUE
In-Reply-To: <m0qSmuj-000I8XC@crynwr.com>
Message-ID: <9407261649.AA05830@ah.com>
MIME-Version: 1.0
Content-Type: text/plain


   Why not generate a random number, checksum it, and sign it using a
   public key?  Or is that overkill?

That's overkill.  For an affordable microprocessor for the price point
of an electronic lock, you can't do a modular exponentiation in a
reasonable amount of time.  A two-second delay is likely too long for
_mass_ market, even if certain markets would bear it.  Sandy also
suggest public key.

A shared secret key for a symmetric cipher is sufficient, since the
binding between a single garage and a single opener is usually not
broken.  If your opener had to work with multiple doors, and if the
usual case pertained where two people share the permission to open
some doors but not others, then public key woudl be needed.

So you can do challenge/response, but there's no need to use public
key.  DES would be sufficient.

Eric





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