Encryption keys: RSA vs. ElGamal

Roscoe eocsor at gmail.com
Mon Nov 26 23:49:43 CET 2007


http://www.samsimpson.com/cryptography/pgp/pgpfaq.html
PGP DH vs. RSA FAQ
Copyright (c) 1999 S.Simpson - All Rights Reserved

A bit old, but I still found it interesting when I read it (wasn't
quite so old then :).

-- Roscoe

On Nov 26, 2007 7:26 PM,  <at120 at hushmail.com> wrote:
> Hello,
>
> I need to create a subordinate key, which will be used for
> encryption only. I tried to find out how RSA differ from ElGamal by
> searching on the web, but I did not find much useful information.
> There are some pages that explain the algorithms in detail, but I'm
> not smart enough to evaluate their security and efficiency just by
> looking at the algorithms.
>
> So it would be great if someone could tell me how they differ when
> it comes to security and efficiency. I know that "A disadvantage of
> the ElGamal system is that the encrypted message becomes very big,
> about twice the size of the original message", and that both seem
> to be limited to use no larger than 4096-bit keys, but that's all I
> know. Please don't give me "they're both secure enough" or "just
> use the defaults" type of answers, I want detailed information.
>
> Are there any patent issues with ElGamal? The Wikipedia article
> mentions nothing about a patent. I found this: "Although the
> inventor, Taher Elgamal, did not apply for a patent on his
> invention, the owners of the Diffie-Hellman patent (US patent
> 4,200,770) felt this system was covered by their patent".
>
> I know that RSA was published in 1977, and the patent on it ran out
> in 2000. ElGamal is from 1984, so if there's a patent on it, will
> it expire/has it expired in 2007?
>
> -AT
>
>
> --
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