Re: Cypherpunk Certification Authority

At 11:20 AM 11/25/95 -0800, you wrote:
>At 01:53 AM 11/26/95 -0800, anonymous-remailer@shell.portal.com wrote:
>>You'd rather sign before encryption??
>>Doesn't that give you "known plain-text" to attack?
>
>The signature is not known unless the whole message being signed is
>known.

Signatures often have known, or easily guessed, plaintext in them,
like the signer's name or ID number, or various header fields
such as X.509's equivalent to ----- BEGIN PGP ....

>And any encryption scheme that is vulnerable to known plaintext attack
>where only a part of the message is known, is worthless anyway.

DES isn't worthless.  It's a bit weak, but not worthless.
#--
#				Thanks;  Bill
# Bill Stewart, Freelance Information Architect, stewarts@ix.netcom.com
# Phone +1-510-247-0663 Pager/Voicemail 1-408-787-1281

Hello,

On Mon, 27 Nov 1995, Bill Stewart wrote:

> Signatures often have known, or easily guessed, plaintext in them,
> like the signer's name or ID number, or various header fields
> such as X.509's equivalent to ----- BEGIN PGP ....

  If the signature is padded with random junk on the end, then it makes 
it harder to do a known text attack.  There was a message a few days ago 
by Anderson and someone else (in England) that dealt with weaknesses in 
some encryption protocols.  It was good to read.

> DES isn't worthless.  It's a bit weak, but not worthless.

  Even though he didn't have proof Bruce Schneier stated in "Applied 
Cryptography 2nd Ed" that the NSA might have a machine that can crack DES 
in 15 mins, and maybe as low as 3-5, as one was built and sold.  The book 
can explain it more, as I am doing this from memory.
  Take care and have fun.
 
==========================================================================
James Black (Comp Sci/Comp Eng sophomore)
e-mail: black@eng.usf.edu
http://www.eng.usf.edu/~black/index.html
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