9 ms·

I can't agree on embedded devices. They have plenty of peripherals that can act as sensors, where you can draw entropy seeds from. You can even leave an empty

I can't agree on embedded devices. They have plenty of peripherals that can act as sensors, where you can draw entropy seeds from. You can even leave an empty pin with a PCB trace to act as a crude antenna and pick up garbage RF. You can use the built in RC oscillator as a crude temperature sensor. My point is, if you're creative, embedded systems offer you so many options without any added cost.

jwandborg 5y ago
You're probably right, the issue might be that there's no standard way for an OS to hook into that.
- AussieWog93 5y ago
  The embedded systems that GP is referring to generally don't have a full-stack OS; hardware access is performed by directly reading to/writing from registers.
smaudet 5y ago
Hmm good points, but you also ignore the power costs here - using oscillators, open pins as thermometers and rf antennas requires additional power draw, not to mention modifying these devices may be nearly impossible due to their embedded nature. Even presuming you modify the hardware/firmware, the additional cycles to handle and process the sensor data mean additional power draw compared to normal operation (embedded devices may frequently power down to wake from some interrupt to save power, additionally not all instructions turn on the same number of transistors - floating point ops require more power than simple branch instructions) - something again that prohibits doing this easily. So "without any added cost" is simply untrue. The reality is that randomness is relatively expensive, whether via hardware or software. Phones have more sensors - they also have massively complex SoCs and large batteries, which still are drained often over the course of a single day. They also tend to cost 1k+ USD, at least for flagship models (prices go as low as 50$ these days, but this is more from economies of scale and resale value economics than because phone hardware/software is suddenly cheap to manufacture)
- stevenhuang 5y ago
  None of that is at all expensive. Reading from RF trace does not take any more power than any other analog pin voltage measurement. Running a few more instructions to "process" (not as if there's much processing needed) the sensor readings is also hardly measurable.
- deleted 5y ago
  [deleted]
gotaquestion 5y ago
You don't even need sensors. STMicroelectronics has a TRNG block [1] that "passes" NIST SP 800-22 statistical analysis [2]. I used quotes because the 800-22 is an analysis test suite and the notion of passing is based on your hypothesis parameters, but the suite itself is considered the de-facto analysis mechanism. I don't follow where the confusion is coming from? [1] https://www.st.com/resource/en/application_note/dm00073853-stm32-microcontroller-random-number-generation-validation-using-the-nist-statistical-test-suite-stmicroelectronics.pdf https://www.st.com/resource/en/application_note/dm00073853-s... [2] https://csrc.nist.gov/Projects/Random-Bit-Generation/Documentation-and-Software https://csrc.nist.gov/Projects/Random-Bit-Generation/Documen...
GekkePrutser 5y ago
The problem with using pins to pick up 'garbage' RF is that an attacker can transmit some actual RF and make your entropy a lot more predictable. A real randomness source would be really great to have in pretty much every computing device these days, considering the widespread use of encryption.
- ChuckNorris89 5y ago
  Agreed, but my example was for very low cost embedded systems where that makes sense like super cheap IoT sensors where every fraction of a cent is accounted for. If your security threat profile has to account for actors with the resources to perform reverse engineering of your hardware, side channel analysis and RF injection, then we're already way out of the realm of low cost devices.

jwandborg 5y ago

You're probably right, the issue might be that there's no standard way for an OS to hook into that.

AussieWog93 5y ago
The embedded systems that GP is referring to generally don't have a full-stack OS; hardware access is performed by directly reading to/writing from registers.

smaudet 5y ago

Hmm good points, but you also ignore the power costs here - using oscillators, open pins as thermometers and rf antennas requires additional power draw, not to mention modifying these devices may be nearly impossible due to their embedded nature. Even presuming you modify the hardware/firmware, the additional cycles to handle and process the sensor data mean additional power draw compared to normal operation (embedded devices may frequently power down to wake from some interrupt to save power, additionally not all instructions turn on the same number of transistors - floating point ops require more power than simple branch instructions) - something again that prohibits doing this easily. So "without any added cost" is simply untrue. The reality is that randomness is relatively expensive, whether via hardware or software. Phones have more sensors - they also have massively complex SoCs and large batteries, which still are drained often over the course of a single day. They also tend to cost 1k+ USD, at least for flagship models (prices go as low as 50$ these days, but this is more from economies of scale and resale value economics than because phone hardware/software is suddenly cheap to manufacture)

stevenhuang 5y ago
None of that is at all expensive. Reading from RF trace does not take any more power than any other analog pin voltage measurement. Running a few more instructions to "process" (not as if there's much processing needed) the sensor readings is also hardly measurable.
deleted 5y ago
[deleted]

gotaquestion 5y ago

You don't even need sensors. STMicroelectronics has a TRNG block [1] that "passes" NIST SP 800-22 statistical analysis [2]. I used quotes because the 800-22 is an analysis test suite and the notion of passing is based on your hypothesis parameters, but the suite itself is considered the de-facto analysis mechanism. I don't follow where the confusion is coming from? [1] https://www.st.com/resource/en/application_note/dm00073853-stm32-microcontroller-random-number-generation-validation-using-the-nist-statistical-test-suite-stmicroelectronics.pdf https://www.st.com/resource/en/application_note/dm00073853-s... [2] https://csrc.nist.gov/Projects/Random-Bit-Generation/Documentation-and-Software https://csrc.nist.gov/Projects/Random-Bit-Generation/Documen...

GekkePrutser 5y ago

The problem with using pins to pick up 'garbage' RF is that an attacker can transmit some actual RF and make your entropy a lot more predictable. A real randomness source would be really great to have in pretty much every computing device these days, considering the widespread use of encryption.

ChuckNorris89 5y ago
Agreed, but my example was for very low cost embedded systems where that makes sense like super cheap IoT sensors where every fraction of a cent is accounted for. If your security threat profile has to account for actors with the resources to perform reverse engineering of your hardware, side channel analysis and RF injection, then we're already way out of the realm of low cost devices.