Wi-Fi (802.11x) - Что это такое? (Новости)
Выпуск № 16 от 9.11.2004.
Тема:
WPA security cracked
Is your wireless network open to attack?
By John Cox, Network World Fusion
A dictionary attack tool designed to exploit a weakness the Wi-Fi
Protected Access security for wireless LANs has been published on the
Web.
The software, called WPA Cracker, exploits one option that can
be used in WPA, usually in consumer applications or residential WLANs:
a pre-shared encryption key. This key is simpler to use and deploy than
using the more complex 802.1x for authentication.
With the pre-shared key, a common shared pass phrase is set for
users and the WLAN access point. This phrase and the Service Set
Identifier (SSID) - the network name - of the WLAN access point then
are changed via an algorithm into an encryption key used to scramble
the packets between clients and the access point.
The weakness was first reported by Wi-Fi Networking News.
WPA Cracker is available at tinypeap.com, which also offers a very
compact Radius server supporting 802.1x authentication using PEAP as
its authentication protocol, designed to run on WLAN access points such
as the Linksys WRT54G.
The WPA vulnerability was first disclosed a year ago in a
paper. The author, Robert Moskowitz, a senior technical director as
ICSA Labs, noted that using the pre-shared key broadcasts in the clear
certain information needed to create and verify the session encryption
key. This information can be recovered and then subjected to an offline
dictionary attack, usually with a program that runs through words and
character combinations until it finds the original pass-phrase.
The attack will not work against nets that don't use the
pre-shared key option. But Moskowitz paints a disturbing picture for
those that do rely on it, saying this attack is even easier than those
mounted against the original WLAN encryption scheme called WEP. WPA was
designed to correct key weaknesses in WEP.
"As the WPA standard states, passphrases longer than 20
characters are needed to start deterring (dictionary) attacks. This is
considerably longer than most people will be willing to use," he
writes. "This offline attack should be easier to execute than the WEP
attack."