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BoardGameGeek» Forums » Board Game Design » Design Theory

Subject: Zero Knowledge Diet Contest. rss

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guy
Wallis and Futuna
Grand Bois Du Nord
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mb
The hospital where I worked wanted to sponsor a friendly weight loss competition so people would have a support structure for their goals. Made sense, but I talked to several people who wanted to join, but were uncomfortable about having their weight known.

So I designed a way to have a weight loss competition in which everyone is assumed to be untrusted and therefore the weighings must be done in front of the entire group. The usual rules apply: the weight you are this week is subtracted from your weight last week to get a loss figure. But no one can find out anyone else's actual weight.

This does require some equipment and a multi-lockable storage closet. But once setup, public weighings without knowledge are possible. Here's how:

Each person brings in a padlock and a cardboard box, filled with whatever, sealed with tape. No one but the owner may carry, lift, or handle the box, but everyone (including the owner) must sign the tape. It is placed in storage with everyone else's box. The storage facility is locked with everyone's padlock.

To record your weight, you get your box, carry it to the scale and get on. When the weight is recorded, you put your box back.

Since no one knows what is in each box or how much it weighs (that's why no one may lift another's box), no one knows your true weight. But if you lost 5 pounds this week, your weight will be 5 pounds less.

The locks and signatures are to prevent anyone else from tampering with or testing the boxes when no one is looking.

The downside is everyone will read heavier, which may be a disincentive. But it fulfills the design criteria.
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Blake T
United States
Arizona
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Clever idea, but it seems like a hassle to deal with the boxes. And if you're still displaying the total weight it seems like people can still get a close estimate; how heavy could a hand-held box really be?

Couldn't you just hide the total weight and only display the change from one week to the next?
 
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guy
Wallis and Futuna
Grand Bois Du Nord
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mb
gvblake22 wrote:
Couldn't you just hide the total weight and only display the change from one week to the next?

Not technically. Obviously, you can run a contest with trusted individuals for practical purposes. However, such a contest could not be called zero-knowledge.

Also, I think an uncertainty of up to 70 pounds (considered maximum liftable by UPS) is enough to introduce more uncertainty in people's true weight than you'd have by just looking at them.

 
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