PGP flaw could let unauthorized people decode sensitive e-mail

[InfoSec News <isn () c4i org>]

http://www.siliconvalley.com/mld/siliconvalley/news/editorial/3845811.htm

Sun, Aug. 11, 2002

NEW YORK (AP) - Snoopers on the Internet could decode sensitive e-mail
messages simply by tricking recipients into hitting the reply button,
computer security researchers warned Monday.

The flaw affects software using Pretty Good Privacy, the most popular
tool for scrambling e-mail.

Researchers at Columbia University and Counterpane Internet Security
Inc. found that someone intercepting an encrypted message could
descramble it by repackaging the message and passing it on to the
recipient.

The message would appear as gibberish, possibly prompting the
recipient to request a resend.

If the recipient includes the original text with that request -- as
many people have their configured their software to do automatically
when they reply -- the interceptor could then read the original
message.

Bruce Schneier, Counterpane's chief technology officer, said most
people would never dream that security can be compromised simply by
returning gibberish.

Intercepting a message is trivial using software known as sniffers,
and companies may use such programs to monitor employees on its
network. An oppressive government may snoop on its citizens if it also
controls service providers or other access points.

Thus, human rights workers, some FBI agents and even the son of a
jailed mobster have used PGP to encrypt messages sent over the
Internet and data stored on computers.

So powerful is the technology that the U.S. government until 1999
sought to restrict its sale out of fears that criminals, terrorists
and foreign nations might use it.

Jon Callas, principal author of the OpenPGP standard at the Internet
Engineering Task Force, said the vulnerability is serious but very
difficult to exploit.

And, he said, many PGP software packages compress messages before
sending. Researchers found that such compression can sometimes thwart
the unauthorized decoding.

Nonetheless, an update to the OpenPGP standard was to be released
Monday to coincide with the announcement of the flaw. Many developers
already have begun to write software fixes, Callas said.

In the meantime, Schneier and Callas urged recipients of PGP e-mail to
avoid including full text of messages when replying.

Schneier and co-researchers Kahil Jallad and Jonathan Katz, who were
at Columbia University when they discovered the flaw, identified its
possibility about a year ago. The latest paper offered a demonstration
of the flaw in practice.

The findings come weeks after researchers at eEye Digital Security
Inc. discovered that hackers could exploit a programming flaw in
companion software -- a plug-in for Microsoft Corp.'s Outlook program
-- to attack a user's computer and in some cases, unscramble messages.

In neither case does the flaw affect the actual encrypting formulas
used to scramble messages.


On the Net:

Research paper: http://www.counterpane.com/pgp-attack.html PGP site:
http://www.pgpi.org




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