You're the expert, but I'm not entirely happy with this: The entropy does not depend on the implementation but what the dev says. While the dev should know what he does, there is still a difference between `Date.now` and `Performance.now`, and that is not accounted for in the current setup. 

If you want to keep the "pass entropy to generator", I suggest limiting the entropy depending on the entropy generator that is used:  

```javascript
_addCurrentTimeToEntropy: function (maxEntropy) {
  if (window && window.performance && typeof window.performance.now === "function") {
    maxEntropy = Math.max(3, maxEntropy|0); // force integer, upper limit 3
    sjcl.random.addEntropy(window.performance.now(), maxEntropy, "eventtime");
  } else {
    maxEntropy = 0;
    sjcl.random.addEntropy((new Date()).valueOf(), maxEntropy, "eventtime");
  }
}
```

Though I'd just give `Performance.now()` a fixed entropy of `2` or `3` or higher (and `Date.now()` of `0`), because it is guaranteed that each call to it returns a different result.