<i>&gt; you&#x27;d just buy a real TRNG</i><p>But then you have a blackbox and are forced to trust the manufacturer.<p>(And as the Snowden revelations show, you have to care about man-in-the-middle attacks over the postal system, while that blackbox is on the way to you.)<p>To add some tinfoil-hat mentality on top of that: I believe it is easier to manipulate a blackbox TRNG than it is to manipulate individual components (transistors, etc.).<p>So although the DIY approach has the downside that you may get things wrong, it has the upside that it is very hard to manipulate.