Are there any use cases for which a good CSPRNG, with a fixed 256-bit seed at process startup from &#x2F;dev&#x2F;urandom or equivalent, is not fast enough?<p>Last time this came up on HN, I measured individual reads from &#x2F;dev&#x2F;urandom, and <i>those</i> are fast enough for many large-scale applications, like one per tweet: <a href="https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=10608843" rel="nofollow">https:&#x2F;&#x2F;news.ycombinator.com&#x2F;item?id=10608843</a><p>(Obviously there are bad CSPRNGs, but there are also bad non-CS PRNGs. So let&#x27;s not count those.)