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Hertzbleed: most AMD / Intel processors vulnerable

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Written by Guillaume
Publication date: {{ dayjs(1655740834*1000).local().format("L").toString()}}
This article is an automatic translation

The encryption keys manipulated by processors no longer seem to be such a well-kept secret.

For a few days now, a word has been appearing on many news sites specialized in computer security: Hertzbleed. This is a term for a new attack called "auxiliary channel" which seems to target AMD or Intel processors indiscriminately, regardless of their generation. On the principle, its operation is quite simple and relies on a very practical ability of "modern" processors: the ability to adjust their operating voltage and frequency as needed.

The problem is that a group of American researchers have noticed that by analyzing the behavior of our processors in this way, it is possible to steal encryption keys manipulated by the chip. The researchers contacted AMD and Intel who quickly recognized the problem. AMD explained that all its Threadripper processors are affected. The same goes for Ryzen processors from the 2000 series to the 5000 series, for the Athlon and for the 1st and 2nd generation of EPYC processors. On the Intel side, it's much simpler since all the brand's processors are affected by the vulnerability.

The group of researchers believes that x86 processors may not be the only ones affected by the problem and they also mention the possibility that it also concerns ARM chips without the thing being proven yet.

If we can imagine that future processors signed by AMD and Intel will be protected against Hertzbleed, the two companies have not planned to deploy patches to counter this attack. Some people have advised to disable Turbo Boost functions at Intel and Precision Boost at AMD to reduce the possibility of attack, but 1/ this does not ensure 100% protection and 2/ it has a considerable impact on performance. Intel believes that the effect of this manipulation is derisory since its processors continue to vary frequencies and voltages even without the Turbo Boost.

Both AMD and Intel advise software developers to use techniques like hiding and masking to limit the impact of this attack. There is also talk of using key rotation, but again, the effects are only partial. That said, the director of security communications at Intel - Jerry Bryant - is reassuring that Hertzbleed is unlikely to affect users: " Although this problem is interesting from a research point of view, we do not believe that this attack is reproducible outside of a laboratory environment. To be continued..