The purpose of my question is get an better idea about reasonable amount of time the generation of the RSA public/private keypair should take?
To be less vague let me specify the question and define I would use these commands to generate the keypair on an laptop running a recent 3.2.xx linux kernel.
$ openssl genrsa -out testkey.private 2048 $ openssl rsa -in testkey.private -pubout -out testkey.public
I have timed about commands and in average this operation is taking about 0.5 seconds, which seems awfully quick to me (too quick indeed).
Know I am aware of (and also tried to express that in the questions title) that it is not merely the time, but rather the amount of entropy and its rate of replenishment which influences the time needed to create the keypair. At least I assume that entropy is used to generate the keys (else the keys would be predictable and consequently useless, right?).
On the same system using
gpg --gen-key from OpenPGP "GNU Privacy Guard" which I can also also be used to create a 2048bit RSA key-pair for instance takes much much longer time and even requires me to move the mouse around etc.
So I am wondering how this is adding up. In essence how much entropy and consequently time should a RSA keypair generation take on a moderns system.
I am convinced there is no standard time, but surely it can be estimated in terms of "less then 30 minutes" "more then 10 seconds".
Given that there are storages of "entropy" in the system. Let's assume they are empty and hence the time I am looking for the creation of one RSA 2048 keypair "rule of thumb" should involve starting from scratch "in entropy storage terms".
Why would OpenPGP
gpg take about 2 minutes to create a RSA 2048 keypair and
openssl be done in half a second...?