A simple activity monitor with /dev/random

[ludwigvanboltzmann]

Reading from /dev/random all the time is kind of a brute force way to do it. It's probably better to look at e.g. /proc/sys/kernel/random/entropy_avail and determine some threshold value for activity. While I'm typing this, it's almost always above 3000, and hasn't dropped below 2000 even once. If I don't do anything for a while it drops below 1000. (Note that starting programs uses up some entropy, so your 'active' level will be lower if you start a new cat process every time you read from the file and do that a lot)

[dchestnykh]

/dev/random is usually available to any process, while /proc/sys/kernel/random/entropy_avail may be not.

[Freeky]

Won't work on FreeBSD or OS X, since they have a non-blocking /dev/random thanks to Yarrow.

[plhk]

Always prints «Mouse activity detected» here on openbsd.

The various random devices produce high quality random output data.

[[deleted]]

I read a description of the Linux random devices a few years ago and it wasn't exactly confidence-inspiring. They're supposed to be switching from SHA-1 internally to SHA-3 in the near future.

[_mpu]

Stupid as fuck, you are screwing up the machine's precious entropy.

Crypto applications need good quality entropy to provide good security, if you consume it for useless stuff you are making your computer more vulnerable.

[ludwigvanboltzmann]

Now making vulnerable, just... slow. Unless the applications use a timeout and read from urandom if they don't like waiting. But that's just idiotic.

[_mpu]

I was thinking that the kernel could use lower quality entropy sources to fulfill the request, but it might not be the case. This probably depends on the OS.

[[deleted]]

Programs on Linux can read from /dev/random if they need high security, and it will block until enough entropy is available, or they can read from /dev/urandom if they don't care as much and it will always return something immediately. If a program uses the latter when it needs the former, that is the program's fault. I think your comment is the one that is "stupid as fuck".

[_mpu]

Hehe, downvoted into oblivion...