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What does entropy _ avail really show in random?
First, the claim that ” /proc/sys/kernel/random/entropy_avail simply gives you the number of bits that can currently be read from /dev/random ” is false. The entropy_avail field reads the input_pool.entropy_count, the “output” pool refers to the pool used for urandom (non-blocking pool) and random (blocking pool).
What is the proper definition of computer science ” entropy “?
What is the proper definition of computer science “entropy”? In computing, entropy is the randomness collected by an operating system or application for use in cryptography or other uses that require random data.
When is entropy taken from the input pool?
If this value is non-zero, entropy is only taken from the input pool if at least urandom_min_reseed_secs seconds have elapsed since the last transfer. By default this value is set to 60 seconds. The last point finally explains why you see an entropy drain in the input pool every 60 seconds.
What does it mean if entropy grows too much?
If entropy grows too much, something is “eating” it to return to the 700-800 range. If I reboot the device, the entropy is still being eaten each minute, but in a smaller chunks thus enabling it to grow again to 700-800 range. How shall I interpret the graphs? What is happening?
Why do I keep losing bits of entropy?
For monitoring the entropy pool without draining it you can try the entropy-watcher program (see linked answer). Watching the entropy-watcher numbers closely it seems that you lose about 64 bits of entropy at intervals. Based on the analysis in the other answer, this seems to be the result of moving entropy to an “output pool” to avoid wasting it.
What does the entropy _ avail field in ASLR mean?
The entropy_avail field reads the input_pool.entropy_count, the “output” pool refers to the pool used for urandom (non-blocking pool) and random (blocking pool). As mentioned in this answer, spawning new processes consumes entropy for things like ASLR.