If pgpverify is installed as part of INN, it uses INN's configuration to determine what signature verification program to use, how to log errors, what temporary directory to use, and what keyring to use. Otherwise, all of those parameters can be set by editing the beginning of this script.
By default, when running as part of INN, pgpverify expects the PGP key ring to be found in pathetc/pgp (as either pubring.pgp or pubring.gpg depending on whether PGP or GnuPG is used to verify signatures). If that directory doesn't exist, it will fall back on using the default key ring, which is in a .pgp or .gnupg subdirectory of the running user's home directory.
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, appropriate use of the signcontrol and pgpverify programs 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 administrators properly protect their PGP private keys, the only way a malicious user could forge a validly-signed control message would be by breaking the public key encryption algorithm, which (at least at this time) is believed to be prohibitively difficult for PGP keys of a sufficient bit length.
<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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