5 ms·

All it does is messuring power consumtion and uses knowledge about the implementation to calculate the key. Unless steps have been taken to equal power consump

All it does is messuring power consumtion and uses knowledge about the implementation to calculate the key. Unless steps have been taken to equal power consumption between different paths, theoretically there is nothing stopping this from working on a hw implementaion of AES.

devdoomari 9y ago
...how about a random-power-consumer? would it help?
- Klathmon 9y ago
  Generally mitigations like adding random things only delay attacks like this, they don't prevent them. Like adding random timings won't prevent timing attacks, adding random sized strings won't prevent chosen plaintext or padding attacks, etc...
  - Gibbon1 9y ago
    Wonder if you can hash the cryto algorithm.
    - Dinux 9y ago
      This was even tested with CTR and GCM (I know this for a fact), which were not a problem at all. Surprisingly GCM was somewhat easier than hashing modes. But also CBC was detectable after a few blocks.
- dom0 9y ago
  No, not at all. A raised SNR can be overcome in almost all circumstances by making more measurements, i.e. correlation, since noise is not correlated, it is removed. For the same reason random delays don't help against timing attacks.
  - tinus_hn 9y ago
    Perhaps you could quantize the level.
  - Ferofluid 9y ago
    Not if you calculate keys nonstop, then have another machine pick from a huge list later.
  - Cyph0n 9y ago
    That's how DPA works as far as I understand.
  - Drdrdrq 9y ago
    Curious: how about generating noise which is correlated to signal and actively tries to modify output to some "random" noise?
- laydn 9y ago
  Cryptography Research (now RAMBUS) developed solutions against these DPA attacks. Real solutions are much more complex than just "random-power-consuming" See: https://www.rambus.com/security/dpa-countermeasures/ https://www.rambus.com/security/dpa-countermeasures/
dom0 9y ago
> theoretically Hardware implementations are designed to make this hard. They also use a lot less power, so any measurements are more difficult / take longer.
user5994461 9y ago
There is a paper on stealing RSA keys, by listening to the sound the power supply of a laptop makes, from 4 meters away with a microphone. Works wonders!
- JoachimSchipper 9y ago
  You're referring to https://www.tau.ac.il/~tromer/acoustic/ https://www.tau.ac.il/~tromer/acoustic/ and the line of related papers. That's absolutely great work, but this work uses very different techniques: the authors of that line of papers feed inputs to the crypto core that amplify the dependency on the key, e.g. by ensuring that a square-and-multiply does all or no squares depending on a single bit of the key. AES doesn't have the kind of algebraic structure that would allow such amplification, so we mostly have to do it the hard way. Fortunately, we had some very talented interns and significant in-house (analog and digital) signal processing expertise. (From colleagues' previous jobs.)

devdoomari 9y ago

...how about a random-power-consumer? would it help?

Klathmon 9y ago
Generally mitigations like adding random things only delay attacks like this, they don't prevent them. Like adding random timings won't prevent timing attacks, adding random sized strings won't prevent chosen plaintext or padding attacks, etc...
- Gibbon1 9y ago
  Wonder if you can hash the cryto algorithm.
  - Dinux 9y ago
    This was even tested with CTR and GCM (I know this for a fact), which were not a problem at all. Surprisingly GCM was somewhat easier than hashing modes. But also CBC was detectable after a few blocks.
dom0 9y ago
No, not at all. A raised SNR can be overcome in almost all circumstances by making more measurements, i.e. correlation, since noise is not correlated, it is removed. For the same reason random delays don't help against timing attacks.
- tinus_hn 9y ago
  Perhaps you could quantize the level.
- Ferofluid 9y ago
  Not if you calculate keys nonstop, then have another machine pick from a huge list later.
- Cyph0n 9y ago
  That's how DPA works as far as I understand.
- Drdrdrq 9y ago
  Curious: how about generating noise which is correlated to signal and actively tries to modify output to some "random" noise?
laydn 9y ago
Cryptography Research (now RAMBUS) developed solutions against these DPA attacks. Real solutions are much more complex than just "random-power-consuming" See: https://www.rambus.com/security/dpa-countermeasures/ https://www.rambus.com/security/dpa-countermeasures/

dom0 9y ago

> theoretically Hardware implementations are designed to make this hard. They also use a lot less power, so any measurements are more difficult / take longer.

user5994461 9y ago

There is a paper on stealing RSA keys, by listening to the sound the power supply of a laptop makes, from 4 meters away with a microphone. Works wonders!

JoachimSchipper 9y ago
You're referring to https://www.tau.ac.il/~tromer/acoustic/ https://www.tau.ac.il/~tromer/acoustic/ and the line of related papers. That's absolutely great work, but this work uses very different techniques: the authors of that line of papers feed inputs to the crypto core that amplify the dependency on the key, e.g. by ensuring that a square-and-multiply does all or no squares depending on a single bit of the key. AES doesn't have the kind of algebraic structure that would allow such amplification, so we mostly have to do it the hard way. Fortunately, we had some very talented interns and significant in-house (analog and digital) signal processing expertise. (From colleagues' previous jobs.)