if /dev/random decides that it has not not enough entropy sources then reading from it blocks - sometimes it blocks for a minute if the machine has few entropy

if /dev/random decides that it has not not enough entropy sources then reading from it blocks - sometimes it blocks for a minute if the machine has few entropy sources (for example no mouse and no keyboard attached) That's why most libraries use /dev/random to seed their own RNG, he says that's wrong and that /dev/urandom (which does not block) is scary. Usually libraries (openssl,JCE) RNG seeds from /dev/random - this is the internal state of the RNGb; internal state is transformed into next iteration by applying SHA-1 and at each turn some initial bits of internal state are returned as random numbers. of course the library RNG comes from the requirement for a lot of randomness in most protocols, (and for predictable performance, also servers also may need to do a lot of random numbers) of course the article has many points.