RE: PPTP (again)

From: Stout, William (
Date: Fri May 15 1998 - 10:40:35 PDT

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    First of all, apologies to the list and Weld for replying to the wrong
    list.  I kept quiet since I thought no one would notice my dumb mistake
    ;) .  Secondly, these are borderline firewall issues, and probably are
    more appropriate to the firewalls-list than firewall-wizards.  The
    thread of PPTP insecurities is on the NTBUGTRAQ list.  Background:
    Nial Smart said:
    >It seems to me that changing the RC4 key each packet is not enough.
    >Consider the case where an attacker can predict a reasonably large
    >proportion of the (unencrypted) contents of the packets going in one
    >direction, in this case the attacker can simply XOR the ciphertexts to
    >produce the XOR of the plaintexts, then XOR this with the plaintext he
    >knows to produce the plaintexts of the other packet.  
    Weld Pond replied:
    >This is correct.  All that spam you get for "get rich quick" scams is
    >actually data the NSA floods  mailboxes and USENET with so that they
    >have known plaintext passing through encrypted tunnels.
    Which I challenged, noting a limited number of 'wild but true' items I
    know about:
    >- a funded covert (cyberwar) project to compromise some
    >encryption/security products for intelligence purposes (clipper
    >contingency plan), 
    >From confidential sources internal and external to the gov't - also
    makes sense, it's 'what they do', why wouldn't they?
    >- an overt FBI plan to compromise encryption/security products for 'law
    >enforcement' purposes (by Lois Freeh), .
    >- a project to place sniffers on all Internet backbones (via Janet
    (CALEA),, which was actually passed
    as an Act in Congress in 1994 and discussed in an International Law
    Enforcement Conference
    >- and a plan to put 'Mind control' elements of Psychological Warfare on
    >Internet sites & postings (Congress, Porter Gross-R Fla.), 
    CIA Iraq story (password site) San Jose
    Mercury News "Budget cuts hobbled CIA on Iraq, lawmaker says".
    I did find one source for SPAM from the FBI: .
    Bill Stout

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