Timing attack threatens private keys on SSL servers

Elliptic-curve curveball crypto mobe method menace

Beginner's guide to SSL certificates

Security researchers have discovered a "timing attack" that creates a possible mechanism for a hacker to extract the secret key of a TLS/SSL server that uses elliptic curve cryptography (ECC).

Elliptic curve cryptography is a type of public-key algorithm that uses the maths of elliptic curves rather than integer factorisation, which is used by RSA as a one-way function. By using ECC it is possible to provide equivalent levels of difficulty for a brute-force attack as can be provided by the more familiar integer-factorisation approaches, but using smaller key lengths. The approach has benefits for mobile and low-power systems.

Researchers Billy Bob Brumley and Nicola Tuveri have discovered some implementations of elliptic curve cryptography are vulnerable to a form of side-channel attack based on measuring the length of time it takes to digitally sign a message. The attack can be carried out locally or, with greater difficulty, remotely. The researchers validated their research through tests on an OpenSSL Server running ECC that they had established, as explained in the abstract of a research paper by the computer scientists.

This paper describes a timing attack vulnerability in OpenSSL's ladder implementation for curves over binary fields. We use this vulnerability to steal the private key of a TLS server where the server authenticates with ECDSA signatures. Using the timing of the exchanged messages, the messages themselves, and the signatures, we mount a lattice attack that recovers the private key. Finally, we describe and implement an effective countermeasure.

To thwart the attack, the researchers suggest the use of time-independent functions for computational operations on elliptic curves. US-CERT has published an advisory on the attack, warning that there is no immediate fix for the problem. US CERT cautions against the use of "ECDSA signatures and binary curves for authentication" pending the resolution of the problem. ®

Protecting users from Firesheep and other Sidejacking attacks with SSL

More from The Register

next story
Spies would need SUPER POWERS to tap undersea cables
Why mess with armoured 10kV cables when land-based, and legal, snoop tools are easier?
Early result from Scots indyref vote? NAW, Jimmy - it's a SCAM
Anyone claiming to know before tomorrow is telling porkies
Apple Pay is a tidy payday for Apple with 0.15% cut, sources say
Cupertino slurps 15 cents from every $100 purchase
Israeli spies rebel over mass-snooping on innocent Palestinians
'Disciplinary treatment will be sharp and clear' vow spy-chiefs
Hackers pop Brazil newspaper to root home routers
Step One: try default passwords. Step Two: Repeat Step One until success
China hacked US Army transport orgs TWENTY TIMES in ONE YEAR
FBI et al knew of nine hacks - but didn't tell TRANSCOM
Microsoft to patch ASP.NET mess even if you don't
We know what's good for you, because we made the mess says Redmond
NORKS ban Wi-Fi and satellite internet at embassies
Crackdown on tardy diplomatic sysadmins providing accidental unfiltered internet access
prev story


Providing a secure and efficient Helpdesk
A single remote control platform for user support is be key to providing an efficient helpdesk. Retain full control over the way in which screen and keystroke data is transmitted.
WIN a very cool portable ZX Spectrum
Win a one-off portable Spectrum built by legendary hardware hacker Ben Heck
Saudi Petroleum chooses Tegile storage solution
A storage solution that addresses company growth and performance for business-critical applications of caseware archive and search along with other key operational systems.
Protecting users from Firesheep and other Sidejacking attacks with SSL
Discussing the vulnerabilities inherent in Wi-Fi networks, and how using TLS/SSL for your entire site will assure security.
Security for virtualized datacentres
Legacy security solutions are inefficient due to the architectural differences between physical and virtual environments.