Assuming a flawless CSRNG, 128 bits of entropy is more than enough to withstand current attack power. It's hard to predict the future -- quantum computers emplo

Assuming a flawless CSRNG, 128 bits of entropy is more than enough to withstand current attack power. It's hard to predict the future -- quantum computers employing Grover's algorithm could conceivably have 2x or more attack power per unit energy -- but 256 bits should be adequate for a long time. It's fine to use low-grade sources of entropy like timestamps as long as we have enough of it. I might only generate a few bits of actual entropy per second when I move my mouse in somewhat predictable arcs, but if I keep at it for a while, I'll generate 256 bits of entropy eventually.