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The Dangers of Emission Security (EmSec)

Emission security, or Emsec, is about preventing attacks using compromising emanations, namely conducted or radiated electromagnetic signals. It has many aspects. Military organizations are greatly concerned with Tempest defenses, which prevent the stray RF emitted by computers and other electronic equipment from being picked up by an opponent and used to reconstruct the data being processed. Tempest has recently become an issue for electronic voting too, after a Dutch group found they could tell at a distance which party a voter had selected on a voting machine. The smartcard industry has been greatly exercised by power analysis, in which a computation being performed by a smartcard — such as a digital signature — is observed by measuring the current drawn by the CPU and the measurements used to reconstruct the key. These threats are closely related, and have a number of common countermeasures. Researchers have also discovered attacks that exploit stray optical, thermal and acoustic emanations from various kinds of equipment. Such techniques are also referred to as side channel attacks as the information is leaking through a channel other than those deliberately engineered for communication.

Understimation of the effect of EmSec

People often underestimate the importance of Emsec. However, it seems that the world’s military organizations spent as much on it as on cryptography during the last quarter of the twentieth century. In the commercial world, the uptake of smartcards was materially set back in the last few years of that century by the realization that all the smartcards then on the market were extremely vulnerable to simple attacks which required the attacker only to trick the customer into using a specially adapted terminal that would analyze the current it drew during a small number of transactions. These attacks did not involve penetrating the card and thus might leave no trace. Once fielded, they were very much cheaper than probing attacks, and potentially allowed large-scale card-cloning attacks against an unsuspecting cardholder population.

Active and Passive Emsec Measures

Both active and passive Emsec measures are closely related to electromagnetic compatibility (EMC) and radio frequency interference (RFI), which can disrupt systems accidentally. If you fly regularly, you’ll be familiar with the captain saying something like ‘All electronic devices must be switched off now, and not switched on again until I turn off the seat belt sign’. This problem is getting worse as everything becomes electronic and clock frequencies go up. And how do you obey the captain now that more and more devices are ‘always on’ — so that the ‘off’ switch only turns off the green tell-tale light?

Things are set to get worse

As more and more everyday devices get hooked up to wireless networks, and as processor speeds head up into the gigahertz range, all these problems — RFI/EMC, Emsec and various electronic warfare threats — are set to get worse.


Published on Sat 05 January 2019 by Mason Whitworth in Security with tag(s): emsec