pgpverify(8)pgpverify(8)NAMEpgpverify - cryptographically verify Usenet control mes-
sages
SYNOPSISpgpverifyDESCRIPTION
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 program to determine who signed the control message.
If the control message was validly signed, pgpverify out-
puts (to stdout) the User ID of the key ID that signed the
message.
OPTIONS
The pgpverify program takes no options.
EXIT STATUSpgpverify returns the follow exit statuses for the follow-
ing 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.
AUTHOR
David C Lawrence <tale@isc.org>
ENVIRONMENTpgpverify does not modify or otherwise alter the environ-
ment before invoking the pgp program. It is the responsi-
bility 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 public keys for the appro-
priate Usenet hierarchy administrators.
SEE ALSOpgp(1)NOTES
Historically, Usenet news server administrators have con-
figured their news servers to automatically honor Usenet
control messages based on the originator of the control
messages and the hierarchies for which the control
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messages applied. For example, in the past, David C
Lawrence <tale@uunet.uu.net> always issued control mes-
sages for the "Big 8" hierarchies (comp, humanities, misc,
news, rec, sci, soc, talk). Usenet news administrators
would configure their news server software to automati-
cally 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 tem-
porarily) any Big 8 newsgroup they wanted by simply forg-
ing 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 cryptographi-
cally verify control messages before automatically acting
on them. Under the pgpverify system, a Usenet hierarchy
maintainer creates a PGP public/private key pair and dis-
seminates the public key. Whenever the hierarchy main-
tainer 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 appro-
priately essentially eliminates the possibility of mali-
cious 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 hierar-
chy 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 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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