They&#x27;re fine. They&#x27;re sane, straightforward, relatively simple constructions based on hashes, HMAC, and ciphers running in CTR mode. You could make a CSPRNG more complicated, but there&#x27;s not much reason to.<p>The stuff that extends the &quot;state of the art&quot; beyond SP800-90A tends to be system-specific and feature-based. For instance, the &quot;estimators&quot; in the LRNG are an extension to SP800-90A (and a bad idea). Rolling over seed files are another extension.