Your understanding is pretty much correct. To quote DJB [1]: Think about this for a moment: whoever wrote the /dev/random manual page seems to simultaneously b

Your understanding is pretty much correct. To quote DJB [1]: Think about this for a moment: whoever wrote the /dev/random manual page seems to simultaneously believe that (1) we can't figure out how to deterministically expand one 256-bit /dev/random output into an endless stream of unpredictable keys (this is what we need from urandom), but (2) we _can_ figure out how to use a single key to safely encrypt many messages (this is what we need from SSL, PGP, etc.). For a cryptographer this doesn't even pass the laugh test. See also his recent blog post [2]. [1] http://www.mail-archive.com/cryptography@randombit.net/msg04763.html http://www.mail-archive.com/cryptography@randombit.net/msg04... [2] http://blog.cr.yp.to/20140205-entropy.html http://blog.cr.yp.to/20140205-entropy.html