RSA Laboratories

7.22 How are hardware devices made tamper-resistant?

There are many techniques that are used to make hardware tamper-resistant (see Question 7.21). Some of these techniques are intended to thwart direct attempts at opening a device and reading information out of its memory; others offer protection against subtler attacks, such as timing attacks and induced hardware-fault attacks.

At a very high level, a few of the general techniques currently in use to make devices tamper-resistant are:

  • Employing sensors of various types (for example, light, temperature, and resistivity sensors) in attempt to detect occurrences of malicious probing.
  • Packing device circuitry as densely as possible (dense circuitry makes it difficult for attackers to use a logic probe effectively).
  • Using error-correcting memory.
  • Making use of non-volatile memory so that the device can tell if it has been reset (or how many times it has been reset).
  • Using redundant processors to perform calculations, and ensuring that all the calculated answers agree before outputting a result.

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