mt19937 (or preferably SFMT¹) is a great library (and fine for cryptographic purposes if you have a sufficiently random entropy source with which to seed it, and reseed it frequently from your entropy source), but you still have to seed it somehow which is where /dev/(u)random comes in. So it really doesn't solve anything.

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¹ http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/SFMT/index.h...