http://nksecur5aoxbew7x4t2jebk7ordomil3a4xubeamno76zexicppwhiad.onion/how-to-pgp.html
It is a good idea to perform
some other action (type on the keyboard, move the mouse, utilize the
disks) during the prime generation; this gives the random number
generator a better chance to gain enough entropy.
We need to generate a lot of random bytes.