> 1. That two-lock physical method is described, which won't work because there is no mathematical operation that can be applied and removed out of sequence lik

> 1. That two-lock physical method is described, which won't work because there is no mathematical operation that can be applied and removed out of sequence like that which is also both not trivial to break/brute-force and doesn't require a pre-shared value which defeats the objective (if you can arrange to securely share that value then you can use that method to share the original secret). That isn't exactly the issue. The key sharing problem is unavailable in both meat-space and math-space and so is irrelevant in context (it applies just as well to the physical locks). With key sharing not a concern, all you need is for your locks and keys to be commutative. That's easy#1 to do securely. #1 Basically all "secure" cryptography other than a one-time pad is reducible to a "hard" problem, but last I checked those hard problems may have vulnerabilities we haven't discovered. Nobody has proven any of those techniques actually secure. However, that would be a criticism of all modern cryptography, not just commutative locks.