Email Delivery

Receive new posts as email.

Email address

Syndicate this site

RSS | Atom

Contact

About This Site
Contact Us
Privacy Policy

Search


November 2010
Sun Mon Tues Wed Thurs Fri Sat
  1 2 3 4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30        

Stories by Category

Basics :: Basics
Casting :: Casting Listen In Podcasts Videocasts
Culture :: Culture Hacking
Deals :: Deals
FAQ :: FAQ
Future :: Future
Hardware :: Hardware Adapters Appliances Chips Consumer Electronics Gaming Home Entertainment Music Photography Video Gadgets Mesh Monitoring and Testing PDAs Phones Smartphones
Industry :: Industry Conferences Financial Free Health Legal Research Vendor analysis
International :: International
Media :: Media Locally cached Streaming
Metro-Scale Networks :: Metro-Scale Networks Community Networking Municipal
Network Types :: Network Types Broadband Wireless Cellular 2.5G and 3G 4G Power Line Satellite
News :: News Mainstream Media
Politics :: Politics Regulation Sock Puppets
Schedules :: Schedules
Security :: Security 802.1X
Site Specific :: Site Specific Administrative Detail April Fool's Blogging Book review Cluelessness Guest Commentary History Humor Self-Promotion Unique Wee-Fi Who's Hot Today?
Software :: Software Open Source
Spectrum :: Spectrum 60 GHz
Standards :: Standards 802.11a 802.11ac 802.11ad 802.11e 802.11g 802.11n 802.20 Bluetooth MIMO UWB WiGig WiMAX ZigBee
Transportation and Lodging :: Transportation and Lodging Air Travel Aquatic Commuting Hotels Rails
Unclassified :: Unclassified
Vertical Markets :: Vertical Markets Academia Enterprise WLAN Switches Home Hot Spot Aggregators Hot Spot Advertising Road Warrior Roaming Libraries Location Medical Public Safety Residential Rural SOHO Small-Medium Sized Business Universities Utilities wISP
Voice :: Voice

Archives

November 2010 | October 2010 | September 2010 | August 2010 | July 2010 | June 2010 | May 2010 | April 2010 | March 2010 | February 2010 | January 2010 | December 2009 | November 2009 | October 2009 | September 2009 | August 2009 | July 2009 | June 2009 | May 2009 | April 2009 | March 2009 | February 2009 | January 2009 | December 2008 | November 2008 | October 2008 | September 2008 | August 2008 | July 2008 | June 2008 | May 2008 | April 2008 | March 2008 | February 2008 | January 2008 | December 2007 | November 2007 | October 2007 | September 2007 | August 2007 | July 2007 | June 2007 | May 2007 | April 2007 | March 2007 | February 2007 | January 2007 | December 2006 | November 2006 | October 2006 | September 2006 | August 2006 | July 2006 | June 2006 | May 2006 | April 2006 | March 2006 | February 2006 | January 2006 | December 2005 | November 2005 | October 2005 | September 2005 | August 2005 | July 2005 | June 2005 | May 2005 | April 2005 | March 2005 | February 2005 | January 2005 | December 2004 | November 2004 | October 2004 | September 2004 | August 2004 | July 2004 | June 2004 | May 2004 | April 2004 | March 2004 | February 2004 | January 2004 | December 2003 | November 2003 | October 2003 | September 2003 | August 2003 | July 2003 | June 2003 | May 2003 | April 2003 | March 2003 | February 2003 | January 2003 | December 2002 | November 2002 | October 2002 | September 2002 | August 2002 | July 2002 | June 2002 | May 2002 | April 2002 | March 2002 | February 2002 | January 2002 | December 2001 | November 2001 | October 2001 | September 2001 | August 2001 | July 2001 | June 2001 | May 2001 | April 2001 |

Recent Entries

In-Flight Wi-Fi and In-Flight Bombs
Can WPA Protect against Firesheep on Same Network?
Southwest Sets In-Flight Wi-Fi at $5
Eye-Fi Adds a View for Web Access
Firesheep Makes Sidejacking Easy
Wi-Fi Direct Certification Starts
Decaf on the Starbucks Digital Network
Google Did Snag Passwords
WiMax and LTE Not Technically 4G by ITU Standards
AT&T Wi-Fi Connections Keep High Growth with Free Service

Site Philosophy

This site operates as an independent editorial operation. Advertising, sponsorships, and other non-editorial materials represent the opinions and messages of their respective origins, and not of the site operator. Part of the FM Tech advertising network.

Copyright

Entire site and all contents except otherwise noted © Copyright 2001-2010 by Glenn Fleishman. Some images ©2006 Jupiterimages Corporation. All rights reserved. Please contact us for reprint rights. Linking is, of course, free and encouraged.

Powered by
Movable Type

« Weakness in Passphrase Choice in WPA Interface | Main | Microsoft Rolls up XP Wireless Fixes »

November 4, 2003

WPA's Little Secret

Wi-Fi Protected Access (WPA) has a weakness: poorly chosen short human-readable passphrases can be cracked with a robust dictionary attack offline and without access to the network: Robert Moskowitz, the senior techncial director of TruSecure Corp.'s ICSA Labs, has given me permission to post this paper he has written that describes a weakness in the interface design for WPA-equipped access points and adapters.

Robert's paper is rather technical and specific, but I can summarize:

Short, text-based WPA keys can be broken through no fault in the WPA protocol.

The longer summary: If you use the standard interface for WPA key entry and provide a text passphrase that uses words found in dictionaries of fewer than 20 characters, a cracker passively intercepting initial key exchange messages can employ an offline dictionary attack and extract the encryption key, gaining access to the network. Key exchange messages occur at the beginning of a connection between an adapter (station) and an access point; that exchange can be forced to repeat by a cracker sending a disassociate message which forces a new exchange within about 30 seconds. So a cracker can be on and off the network in a couple of minutes with the information they need. This is actually much worse than WEP, but easily solved.

Robert points out that dictionary-based cracking programs abound, and that little modification would be needed to turn one of those into a weak-WPA-key attack.

The fundamentals of WPA remain intact; this is technically an interface problem given that manufacturers know -- as he points out in his paper -- that users won't enter long keys. Microsoft solved this problem with their 128-bit WEP solution for their broadband gateway by writing the key to a floppy disk after it was generated, allowing users to walk the key from machine to machine.

It should be made clear that WEP's flaw were deep within: WEP can be cracked regardless of how good your key selection is or how long the key. With WPA, the length of the passphrase and its quality has a direct relationship to its integrity.

The problem Robert describes isn't unknown; he's just isolated and expanded on it. The solution is also quite simple: choose a key of at least 96 bits or a passphrase that includes gibberish that's more than 20 characters long. So far, of all the WPA interfaces that I've seen, only Apple's allows you to enter raw hexadecimal and they require 64 hex characters (32 bytes or a full 256 bits).

Robert suggests generating a small random value, turning it into its hex equivalent, and then entering those hex digits as a text passphrase to have sufficient randomness. For more information on passphrase weaknesses and strategies for choosing them, Robert refers you to this FAQ.

This shouldn't be the shot heard round the world, but I hope those of you that read this site will take this concern to the manufacturers of Wi-Fi equipment. It's not too late for them to fix this problem by building in the ability to generate random keys that can be copied and pasted simply across systems, and by restricting the ability to enter weak keys by either requiring more characters or running a crack program against your passphrase choice as Unix password programs often do these days.

3 TrackBacks

Wi-Fi Networking News reports that Wi-Fi Protected Access (WPA) is vulnerable to dictionary attacks. This means you gain nothing by turning it on unless you choose a strong WPA key. The best source I've found for creating strong keys is... Read More

Tabs dump 2 from padawan.info on November 5, 2003 5:05 AM

A tabs dump is when I have so many tabs left open in Safari because I thought I might blog... Read More

Tabs dump 2 from padawan.info on May 22, 2004 2:16 PM

A tabs dump is when I have so many tabs left open in Safari because I thought I might blog... Read More