'Many CPUs these days have DVFS (Dynamic Voltage and Frequency
Scaling), which allows the CPU's clockspeed and voltage to vary
dynamically depending on whether the CPU is idling or not. By turning
the voltage up and down with one thread, researchers were able to flip
bits in another thread. By flipping bits when the second thread was
verifying the TrustZone key, the researchers were granted permission.
If number 'A' is a product of two large prime numbers, you can flip a
few bits in 'A' to get a number that is a product of many smaller
numbers, and more easily factorable.
"As the first work to show the security ramifications of energy
management mechanisms," the researchers reported at Usenix, "we urge
the community to re-examine these security-oblivious designs."'
-- source: https://hardware.slashdot.org/story/17/09/23/2113243
Dept. of Computer Science
University of Waikato, NZ
+64 (7) 858-5174