Feeds

Marlinspike demos MS-CHAPv2 crack

‘The strength of a single DES encryption’ not enough

Seven Steps to Software Security

Security researcher Moxie Marlinspike has turned his attention to VPNs based on Microsoft’s MS-CHAPv2 protocol, demonstrating software at Defcon that can capture and crack passwords.

Chapcrack parses the credential information out of MS-CHAPv2 handshakes, which are then sent to Cloudcracker. Cloudcracker will then return a packet that can be decrypted by Chapcrack to recover the password.

As noted by ThreatPost, MS-CHAPv2 is an old protocol that should have been replaced, but hasn’t: criticisms go back as far as 1999.

Marlinspike writes in this blog post, “It shows up most notably in PPTP VPNs, and is also used quite heavily in WPA2 Enterprise environments”.

There is, he writes, “only one unknown in the entire protocol – the MD4 hash of the user’s passphrase, which is used to construct three separate DES keys”. Since the MD4 hash of a user’s password “is enough to authenticate as them”, Marlinspike and collaborator David Hulton of Pico computing made this the focus of Chapcrack.

While El Reg doesn’t propose reproducing Marlinspike’s technical explanation in full, it’s worth a read, if only for the reasoning behind how the attack works: from what looks like a seriously difficult computational task, he and Hulton winnow the problem down to a complexity of 256: “the security of MS-CHAPv2 can be reduced to the strength of a single DES encryption” [original emphasis].

Pico Computing’s key contribution to the effort is in the form of an FPGA-based box that can “crack any MS-CHAPv2 handshake in less than a day”, Marlinspike writes.

Marlinspike says that MS-CHAPv2 should be purged from the Internet, advising that PPTP traffic “should be considered unencrypted”, and that MS-CHAPv2 enterprise users should begin migrating – now. ®

Mobile application security vulnerability report

More from The Register

next story
Yorkshire cops fail to grasp principle behind BT Fon Wi-Fi network
'Prevent people that are passing by to hook up to your network', pleads plod
HIDDEN packet sniffer spy tech in MILLIONS of iPhones, iPads – expert
Don't panic though – Apple's backdoor is not wide open to all, guru tells us
NEW, SINISTER web tracking tech fingerprints your computer by making it draw
Have you been on YouPorn lately, perhaps? White House website?
LibreSSL RNG bug fix: What's all the forking fuss about, ask devs
Blow to bit-spitter 'tis but a flesh wound, claim team
Attackers raid SWISS BANKS with DNS and malware bombs
'Retefe' trojan uses clever spin on old attacks to grant total control of bank accounts
Manic malware Mayhem spreads through Linux, FreeBSD web servers
And how Google could cripple infection rate in a second
Mozilla fixes CRITICAL security holes in Firefox, urges v31 upgrade
Misc memory hazards 'could be exploited' - and guess what, one's a Javascript vuln
Don't look, Snowden: Security biz chases Tails with zero-day flaws alert
Exodus vows not to sell secrets of whistleblower's favorite OS
prev story

Whitepapers

Designing a Defense for Mobile Applications
Learn about the various considerations for defending mobile applications - from the application architecture itself to the myriad testing technologies.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Reducing security risks from open source software
Follow a few strategies and your organization can gain the full benefits of open source and the cloud without compromising the security of your applications.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Consolidation: the foundation for IT and business transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.