Subject: Double Wide SHA-1 & EL Gamal Signatures

From: "William H. Geiger III" <[email-masked]>
Date: Tue, 09 Nov 1999 16:44:10 -0600

Hi,

In my periodic scanning throught the keyserver databaes I have stumbles
across some interesting signatures:

3 Algo 20 sigs [ElGamal (Encrypt or Sign)]

and over 500 Hash 4 sigs [SHA-1 (Double Width)]

Does anyone have any URL's for documentation on the ELGamal Signatures &
the Double Width SHA-1 HASH?

tks,

-- 
---------------------------------------------------------------
William H. Geiger III                    http://www.openpgp.net  
Geiger Consulting    

Data Security & Cryptology Consulting
Programming, Networking, Analysis
 
PGP for OS/2:                   http://www.openpgp.net/pgp.html
---------------------------------------------------------------

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From: Werner Koch <[email-masked]>
Date: Wed, 10 Nov 1999 10:09:21 +0100

> 3 Algo 20 sigs [ElGamal (Encrypt or Sign)]

Probably these are all created by GnuPG.  When I started with GnuPG I
had no info about OpenPGP and used ElGamal for both encryption and
signing using an algo ID of 42.  Later I kept this as an optional 
algorithm for those who really want the large signatures and for a
while I sticked to algo 20 for the encryption subkey until I
recognized all the problems with the keyservers and PGP 5 so the
default is now to create a 17/16 key.

For GnuPG there is no difference between algo 16 and 20.  Both keys 
are not subject to the Bleichenbacher attack and therefore usable for
signatures.

> and over 500 Hash 4 sigs [SHA-1 (Double Width)]

Don't know about this and IMHO a combination of SHA-1 and RipeMD-160
may be better.

BTW, anything new about the rumours that the NSA has a new extendable
hash algorithm with a digest length of up to 512 bits?

  Werner

-- 
Werner Koch at guug.de           www.gnupg.org           keyid 621CC013