Jul 27, 2019

"/dev/random versus /dev/urandom And now we get to the meat of the issue- which output interface to use for "the most demanding cryptographic computational long-term security"? First thing is first- both /dev/random and /dev/urandom are fed data from the same CSPRNG. Let me repeat that, with a bit more emphasis: Both /dev/random and /dev/urandom are fed data from the same CSPRNG. In fact, most who understand this, will explain that you should use /dev/urandom, and NOT /dev/random. The problem is, that /dev/random has the horrible bug of blocking when the input entropy pool is exhausted. So, if your application relies on /dev/random to get random numbers, there are pauses and delays until there is enough entropy in the input pool to reseed the CSPRNG, so you can get more data."