How many random numbers do you need to generate to be able to reasonably verify the distribution is uniform? There could be a well tested lib that does that and that's included by the wallets? I guess...
Yeah it's very tricky. I'm not sure how to make it practical; it has to be the *souce* value that you're testing for uniformity. It doesn't have to be *perfectly* uniform, or even that close. But it has to be like 100 bits of genuine entropy... note for nonces that would not cut it, but for private keys it does. Not easy!
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