Feeds

Crypto attack puts digital sig hash on collision course

SHA-1, your time is near

Seven Steps to Software Security

Cryptographers have found new chinks in a widely-used digital-signature algorithm that have serious consequences for applications that sign email, validate websites, and carry out dozens of other online authentication functions.

The researchers, from Macquarie University in Sydney, Australia, found a way to break the SHA-1 algorithm in significantly fewer tries than previously required. Although the hash function was previously believed to withstand attempts numbering 263, the researchers have been able to whittle that down to 252, a number that puts practical attacks well within grasp of well-funded organizations.

Secure hashing algorithms are designed to reduce text or digital files to a unique series of letters and numbers that is often compared to the document's signature. The findings, which were published Wednesday here (PDF), mean it's easier to create what cryptographers call collisions in SHA-1, in which two different sources share the same the same output.

"I'm expecting that we'll start seeing SHA-1 collisions before the end of the year, if not sooner," said Paul Kocher, president and chief scientist at Cryptography Research, a San Francisco-based consultancy. "For applications that fail because of collisions, you need to be really worried."

Indeed, it was collisions in the now-disgraced MD5 algorithm that allowed independent researchers last year to poke holes in the internet's digital certificate system by forging counterfeit credentials needed to impersonate websites that rely on the security measure. The discovery sent certificate authorities such as VeriSign's RapidSSL scrambling to change the way they issue SSL, or secure sockets layer, certificates.

Other hashes, including SHA-0 and MD4, have also been demonstrated to be weak enough to generate collisions using relatively modest means. With the latest findings, that list is steadily growing.

"Now, SHA-1 has some of the same problems that MD5 has had creeping up on it for a while," Kocher said.

The 160-bit output of SHA-1 should in theory allow hashes to withstand 280 operations without generating a collision. That number came down to 269 and later to 263 as researchers discovered ways to exploit weaknesses in the algorithm. But until now, only the most elite government organizations had the computing power to do that.

Cryptographers have long recognized that advances in computing power and research into weaknesses of various hashing algorithms jeopardize the reliability of digital signatures. Last year, the National Institute of Standards and Technology commenced an open competition to create a new algorithm. The winning entry should be one that is able to withstand attack and able to generate hashes quickly and without consuming too many computer resources. It will offer hashes with as many as 512 bits, enough to (at least theoretically) withstand 2256 attempts to create a collision.

The new attack technique combines what's known as a non-linear differential path with a boomerang attack. It decreases the cost of a collision attack by a factor of more than 2,000 compared with previous methods. The paper has not yet been peer reviewed.

The method works only for collisions, in which an attacker is able to control both messages that are hashed. SHA-1 is still believed to resist what's known as pre-image attacks, in which an attacker tries to create one message that generates the same hash value as a pre-determined message. ®

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
Black Hat anti-Tor talk smashed by lawyers' wrecking ball
Unmasking hidden users is too hot for Carnegie-Mellon
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
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.