From: collins@newton.apple.com (Scott Collins)
Date: Wed, 11 Aug 93 12:02:22 PDT
To: uri@watson.ibm.com
Subject: Re: How long would it take?
Message-ID: <9308111856.AA22501@newton.apple.com>
MIME-Version: 1.0
Content-Type: text/plain


  >How does your "Yes" wash with the next paragraph of your note?

I'm sorry.  My answer was misleading (read 'wrong').  What I was trying to
say was:

  "Yes, but not in a reasonable amount of time."

My implication was that an attack against RSA with a 1264 bit key and an
attack against IDEA with a 128 bit key are both prohibitive, but that my
_guess_ is that cryptanalysis of the IDEA cypher would be the more fruitful
attack.

If the real question is:

  "Am I safe from the NSA when I use PGP and encrypt with a 1264 bit key?"

Then I must answer:

  "In my opinion, you are reasonably safe."

If the question is:

  > Could the NSA reverse PGP encryption on a message that was encrypted with a
  > 1264 bit key?

Then I must answer:

  "Yes, it is mathematically possible; although unlikely in the extreme."



I apologize.

  >Sorry I didn't include more numbers,

...really sorry.  They said what I meant.



  >And IDEA is not susceptible to diff.cryptan  -  that's the way
  >it was *designed* (actually the designer proved mathematically
  >the invinsibility of IDEA to this attack).

Thanks for this info.  I have been trying to get the IDEA papers:

  "Detailed Description and a Software Implementation of the IPES Cipher"
  "Markov Ciphers and Differential Cryptanalysis"

without success, as yet.  Perhaps you have them or know of an ftp site?

Thanks,

Scott Collins         | "Few people realize what tremendous power there
                      |  is in one of these things."     -- Willy Wonka
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