It's also not possible to catch all systematic design flaws. It's possible for someone who is deeply knowledgable in an area like crypto to deliberately introdu

It's also not possible to catch all systematic design flaws. It's possible for someone who is deeply knowledgable in an area like crypto to deliberately introduce strategic design weaknesses into a system that might seem like reasonable choices to anyone who doesn't understand the exact context. I have always been suspicious of Tor's choice of long-lived circuits over packet-level onion routing. It seems like each packet should follow a different path. It would also be easier in a packet-based scheme to implement some level of noise / decoy traffic generation to make statistical analysis of traffic more difficult. It seems like a design choice that would make statistical inference easier by someone who has a God's-eye view of traffic. Large powerful nation states absolutely have this, while smaller ones may not, making it an ideal asymmetric vulnerability. But that's just one example. A true deliberately-introduced weakness might be something far more subtile than this: a choice of order of operations or timing for example.