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pgpverify(8)									     pgpverify(8)

       pgpverify - cryptographically verify Usenet control messages

       pgpverify [ -test ]

       The  pgpverify  program	reads  (on standard input) a Usenet control message that has been
       cryptographically signed using the signcontrol program.	pgpverify then uses the pgp  pro-
       gram  to  determine  who  signed  the control message.  If the control message was validly
       signed, pgpverify outputs (to stdout) the User ID of the key ID that signed the message.

       The ``-test'' flag causes pgpverify to print out the input it is passing to pgp (which  is
       a  reconstructed version of the input that supposedly created the control message) as well
       as the output of pgp's analysis of the message.

       pgpverify returns the follow exit statuses for the following cases:

       0      The control message had a good PGP signature.

       1      The control message had no PGP signature.

       2      The control message had an unknown PGP signature.

       3      The control message had a bad PGP signature.

       255    A problem occurred not directly related to PGP analysis of signature.

       David C Lawrence <tale@isc.org>

       pgpverify does not modify or otherwise alter the environment before invoking the pgp  pro-
       gram.   It  is the responsibility of the person who installs pgpverify to ensure that when
       pgp runs, it has the ability to locate and read a PGP key file that contains the PGP  pub-
       lic keys for the appropriate Usenet hierarchy administrators.


       Historically,  Usenet  news  server  administrators  have configured their news servers to
       automatically honor Usenet control messages based on the originator of  the  control  mes-
       sages  and  the	hierarchies  for which the control messages applied.  For example, in the
       past, David C Lawrence <tale@uunet.uu.net> always issued control messages for the "Big  8"
       hierarchies  (comp, humanities, misc, news, rec, sci, soc, talk).  Usenet news administra-
       tors would configure their news	server	software  to  automatically  honor  newgroup  and
       rmgroup control messages that originated from David Lawrence and applied to any of the Big
       8 hierarchies.

       Unfortunately, Usenet news articles (including control messages) are notoriously  easy  to
       forge.	Soon, malicious users realized they could create or remove (at least temporarily)
       any Big 8 newsgroup they wanted by simply forging an appropriate control message in  David
       Lawrence's name.  As Usenet became more widely used, forgeries became more common.

       The  pgpverify program was designed to allow Usenet news administrators to configure their
       servers to cryptographically verify control messages before automatically acting on  them.
       Under the pgpverify system, a Usenet hierarchy maintainer creates a PGP public/private key
       pair and disseminates the public key.  Whenever the hierarchy maintainer issues a  control
       message,  he uses the signcontrol program to sign the control message with the PGP private
       key.  Usenet news administrators configure their news servers to run the pgpverify program
       on  the	appropriate  control  messages, and take action based on the PGP key User ID that
       signed the control message, not the name and address that appear in the control	message's
       From or Sender headers.

       Thus,  using  the  signcontrol and pgpverify programs appropriately essentially eliminates
       the possibility of malicious users forging Usenet control messages  that  sites	will  act
       upon,  as  such users would have to obtain the PGP private key in order to forge a control
       message that would pass the cryptographic verification step.  If the hierarchy administra-
       tors  properly protect their PGP private keys, the only way a malicious user could forge a
       validly-signed control message would be by breaking the RSA  encryption	algorithm,  which
       (at  least  at this time) is believed to be an NP-complete problem.  If this is indeed the
       case, discovering the PGP private key based on  the  PGP  public  key  is  computationally
       impossible for PGP keys of a sufficient bit length.

       <URL:ftp://ftp.isc.org/pub/pgpcontrol/>	is  where the most recent versions of signcontrol
       and pgpverify live, along with PGP public keys used for hierarchy administration.

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