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[Cfrg] Using Diffie-Hellman With a Non-prime Modulus

Michael D'Errico <mike-list@pobox.com> Wed, 28 October 2020 19:41 UTC

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Date: Wed, 28 Oct 2020 15:38:26 -0400
From: Michael D'Errico <mike-list@pobox.com>
To: cfrg@irtf.org
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Archived-At: <https://mailarchive.ietf.org/arch/msg/cfrg/GZFMRENUhG1tYfhwPXa-0HeLu8M>
Subject: [Cfrg] Using Diffie-Hellman With a Non-prime Modulus
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Hi,

Can someone please point me to a reference showing
how to use Diffie-Hellman where the modulus is not 
a prime number?  Preferably one readable by laymen.

The reason for this is I'm considering looking for 
a modulus M which is not prime, but where M is the 
number between some pair of Twin Primes, and also 
maybe where M is a prime times a power of two.

I found at least one of these: 786431,786433 is a 
twin prime pair with midpoint 3*2^18.

I'd hope to find an M whose odd prime factor is 
very large.

Thanks,

Mike

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