Fun with Protocols

Can he double-load envelopes without being detected in the ones they open? (carbon, order, carbon, order) Maybe by having a secret pocket in the envelope...

 #2

He could just write extra digits onto the uniqueness sequence

 #2

Haha, nice Stereo. A uniqueness sequence, by default for its purposes, is suppose to be of fixed length, but I neglected to mention that. See if you can do #3 now, that one's by far the hardest one.

As for the secret pocket in the envelope, that's pretty insecure. There's a chance that the bank would notice when opening, say, 99 envelopes, or they might have a precise massing machine. They're the ones that define the screening process after all.

I remember something similar to the "open n-1" thing from my cybersecurity course.

That's the basic "Blind Signature" protocol, meant to prevent malicious cheaters from simply getting the bank to blindly sign a money order saying it's worth x factorial amount, or some other magnanimous number that is far beyond your capacity. The same protocol also includes fancy math that does a document scramble or "encryption", rendering it unreadable until you reverse the process.