DH/DSS vs ElGame/DSS?

Robert J. Hansen rjh at sixdemonbag.org
Fri Apr 24 13:50:23 CEST 2009

allen.schultz at gmail.com wrote:
> What is the difference between DH/DSS and ElGamel/DSS? I was reading up
> on S/MIME v3 and PGP/MIME differences when that came up.

I don't know how it's used in the S/MIME standard.  However, the Elgamal
encryption algorithm is often misnamed the Diffie-Hellman encryption

The DH key exchange algorithm (DHKEA) came first, way back in the '70s.
 Then an Egyptian-American named Taher Elgamal did some groundbreaking
work in generalizing DHKEA, discovering the mathematical roots of why it
worked as well as it does, and in the process developed a whole family
of algorithms.  This family is often called the "Elgamal family."  He
also developed the Elgamal encryption and signing algorithms.

It is my understanding that the correct name for what OpenPGP uses is
the Elgamal encryption algorithm.  I don't know why PGP Corporation
calls it Diffie-Hellman encryption; it seems to be an idiosyncratic usage.

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