Three University of Michigan computer scientists say they have found a way to exploit a weakness in RSA security technology used to protect everything from media players to smartphones and ecommerce servers.

RSA authentication is susceptible, they say, to changes in the voltage supply to a private key holder. The researchers – Andrea Pellegrini, Valeria Bertacco and Todd Austin - outline their findings in a paper titled “Fault-based attack of RSA authentication”  to be presented 10 March at the Design, Automation and Test in Europe conference.

"The RSA algorithm gives security under the assumption that as long as the private key is private, you can't break in unless you guess it. We've shown that that's not true," said Valeria Bertacco, an associate professor in the Department of Electrical Engineering and Computer Science, in a statement

The RSA algorithm was introduced in a 1978 paper outlining the public-key cryptosystem. The annual RSA security conference is being held this week in San Francisco.

While guessing the 1,000-plus digits of binary code in a private key would take unfathomable hours, the researchers say that by varying electric current to a secured computer using an inexpensive purpose-built device they were able to stress out the computer and figure out the 1,024-bit private key in about 100 hours – all without leaving a trace.

The researchers in their paper outline how they made the attack on a SPARC system running Linux. They also say they have come up with a solution, which involves a cryptographic technique called salting that involves randomly juggling a private key's digits.

The research is funded by the National Science Foundation and the Gigascale Systems Research Center