On Thursday February 5 2009, David Bolt wrote:
On Thu, 5 Feb 2009, Carlos E. R. wrote:-
On Thursday, 2009-02-05 at 18:44 -0000, David Bolt wrote:
If you'd prefer not to use /dev/urandom , you could change the command to if=/dev/zero instead and have the same effect.
In my machine, it is slow and cpu intensive.
Hmm, using /dev/urandom on my machines, the test transfers were done so fast that I couldn't tell whether it was CPU intensive or not.
Depending on your hardware (might you have a hardware RNG?) this might be expected to be the case at least some of the time. However, keep in mind that there are things for which entropy is required that are more important than giving script kiddies headaches, and pulling a lot of data out of /dev/urandom when there is no hardware RNG can deplete the available entropy and require some time for more to accumulate. And lest this sound like humor, it is not. As largely deterministic machines (a property we generally like in computing), it is not easy to come by true randomness for those times when we need it (mostly cryptographic purposes), so things like interrupts and timers (using the timing relationships between non-synchronized activities and events, if I understand correctly) are used to accumulate entropy to later supply via /dev/random and /dev/urandom. Extracting a lot of random data from these sources depletes the available entropy for a period of time until more can be accumulated. I don't really know at what rate a system can replenish its entropy supply nor what uses are typically made of it (answers to both of which are no doubt highly dependent on the hardware and the use to which it is put), but it's perhaps something for some users to keep in mind.
...
Regards, David Bolt
Randall Schulz -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org For additional commands, e-mail: opensuse+help@opensuse.org