Fixing Biased Entropy: The Von Neumann Unbiasing Trick

TL;DR: I've found that hardware entropy sources are rarely uniform. To solve this, I use Von Neumann Unbiasing, which pairs bits and discards identical results (00, 11). By mapping 01 to 0 and 10 to 1, I can extract a perfectly fair 50/50 distribution from any biased source, provided the bias is constant and bits are independent. I’ve found that hardware is always noisier than you’d expect—and rarely in the way you want. When I pull entropy from thermal jitter or diode noise, I'm dealing with the messy physical world, which doesn't care about my requirement for a perfect distribution. A sensor might lean toward a logic high or low due to temperature fluctuations or voltage drops, and in practice, achieving a perfect 0.5 probability out of a physical component is almost impossible. If I see someone using biased entropy for key generation, I know they're shrinking their effective keyspace and making their system vulnerable to brute-force attacks. A cryptographic key is only as strong as