[se4u]

One alternative implementation of this which is very simple is as follows.

1. User makes a public declaration to always make a prediction using some platform. Like they release a tweet saying all future predictions will happen on futuu.re (or on a Blockchain)

2. They only release the sha hashes of their prediction to futuu.re, along with a date for that prediction, and users keep the true prediction with themselves. At any time before deadline they must reveal the content to the world and tell futuu.re about it. Futuu.re verifies that the sha matches the prediction and keeps an easy record. All predictions must start with a preamble.

3. futuu.re maintains three counters for a use, one showing the number of predictions made till that time, second showing predictions that should be revealed till that time, third showing the number of predictions that have been revealed . This establishes the long time accuracy of the user.

This way when someone reveals their pok then the public will know whether they tried to fool people because the users trust ratio will go down if they make a lot of predictions without revealing them. This is also more secure since the actual content is never stored on the server.

The only thing that needs to be done is to use a content formatter/validator at the time of hash creation for stylstic reasons and to make it convenient for public to verify the accuracy of the user.

[rkangel]

You would need some concept of published identity, otherwise they could just create their predictions against multiple different identities each with e.g. 10 predictions.

[se4u]

So actually this wont be a problem. Basically if they do this then each account that they create will only have very few published predictions. So it will be like a coin which comes up head twice after two tosses. The public will not trust such accounts with low number of correct predictions.

To build trust you'd need to have a high count of revealed predictions in any given account.

That said people can try to game the system by uploading a very large number of predictions programmatically, so I think a rate throttling will have to be enforced. Any account can't make more than one prediction a day or something like that.

Also note that the issue you raised will also affect OP's implementation.

[repartix]

Add cost to post the prediction. At high enough cost it can't be gamed.

edit: and it's also your revenue.