Hi John: * John Siegler <siegs at hotmail.com> [2005-04-07 17:31:10 +0000]: > I apologize if this is the wrong place to ask, but I am simply wondering > what is the best way to obtain the raw readings (low order bits) from the > sensors, in order to calculate randomness. I read in the values from the > /proc/sys/dev/sensors files (using 2.4 kernel), but the values did not seem > to contain the low order bits since the fan speed and cpu temp did not > change much. Is there an easy way to access this data using libsensors, or > will that give me the same not-very-random data? Or is there a driver > available? There's just not enough precision in the measurements to use it as an entropy source. Most of the sensors chips have 8 or 9 bits of precision, with 1/2 degree being the limit. The fan speed sensors are no better. Unless your system temps fluctuate wildly (and randomly!), I think it's not a good use for that. As if that's not bad enough, we rate-limit to somewhere between 30-60 readings per minute; so even if it was a good source of entropy, and you polled the chip constantly (which is not recommended) you wouldn't get a lot of bits (of entropy) out of it. Sorry. If you insist anyway, you could check the datasheet of the sensor chip and drive it directly with the userspace i2c-dev module to get the raw readings. Regards, -- Mark M. Hoffman mhoffman at lightlink.com
