![]() So, cached data is usually much faster to access than data in motherboard RAM. If the CPU keeps track of the RAM addresses (memory locations) that you’ve used recently, and can guess well enough which ones you’re likely to use again soon, it can keep them temporarily in its cache memory and thus greatly speed up your second access to those values, and the third access, the fourth, and so on.įor example, if you’re looking up a series of data values in a table to convert image pixels from one colour format to another, you might find that most of the time the lookup table tells you to visit either RAM address 0x06ABCC00 (which might be where the special code for “black pixel” is stored) or address 0x3E00A040 (which might be the location of the “transparent pixel” code).īy automatically keeping the values from those two commonly-needed memory addresses in its cache, the CPU can short-circuit (figuratively, not literally!) future attempts to access those addresses, so that there’s no need to send electrical signals outside the processor, across the motherboard, and into the actual RAM chips to read out the master copy of the data that’s stored there. …isn’t always quite as invisible as you might think, and may sometimes leak some or all of its content, even to processes that shouldn’t be able to see it.Īs the name suggests, cache memory (it’s pronounced cash, as in dollars and cents, not cachet, as in respect and prestige, if you’ve ever wondered), keeps special copies of data values from conventional RAM in hidden locations inside the CPU chip itself. ![]() We’re not going to try to explain the various forms of this attack at any length, because the technical details of how to take the measurements, and the mathematical modelling used to make inferences from those measurements, are complex.īut the core of the problem, if you will pardon the partial pun, is that the cache memory that’s buried inside modern processor chips, intended to provide an invisible and automatic performance boost… The researchers behind this new paper are Andreas Kogler, Jonas Juffinger, Lukas Giner, Martin Schwarzl, Daniel Gruss and Stefan Mangard from Graz University in Austria, and Lukas Gerlach and Michael Schwarz of the CISPA Helmholtz Center for Information Security in Germany. ![]() Collide cached data, and measure the power required ![]()
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