Contents
Where does Dev random get entropy?
entropy pool
/dev/random : very high quality of randomness, extracted directly from the entropy pool (itself fed mostly by peripherals interrupts timings and block devices seek times); it will block if you request more bits than available in the entropy pool (as reported by cat /proc/sys/kernel/random/entropy_avail )
What does entropy source mean?
Definition(s): A physical source of information whose output either appears to be random in itself or by applying some filtering/distillation process. This output is used as input to either a RNG or PRNG.
How do you find the entropy of a source?
Entropy can be calculated for a random variable X with k in K discrete states as follows: H(X) = -sum(each k in K p(k) * log(p(k)))
How to add entropy to the / dev / random device?
I have a device which generates some noise that I want to add to the entropy pool for the /dev/random device in an embedded Linux system. I’m reading the man page on /dev/random and I don’t really understand the structure that you pass into the RNDADDENTROPY ioctl call.
How to add entropy to a Rand pool?
The following structure is used: struct rand_pool_info { int entropy_count; int buf_size; __u32 buf [0]; }; Here entropy_count is the value added to (or subtracted from) the entropy count, and buf is the buffer of size buf_size which gets added to the entropy pool. Is entropy_count in this structure the number of bits that I am adding?
What happens if you guess low on entropy?
If you guess low, the worst that will happen is that /dev/random will block sooner than it otherwise would have. If you guess high, /dev/random will operate like /dev/urandom for a little bit longer than it otherwise would have before it blocks. You can guesstimate based on the “quality” of your entropy source.
What is the entropy of a random noise generator?
Sure, if the data came from a good, unpredictable and equal-distributed hardware random noise generatr the entropy (in bits) is 8*size of the buffer (in bytes). But if the bits are not equally distributed or are somehow predictable the entropy becomes less.