ProveIt

At long last, we have the technology. You can finally prove to your friends that you liked that band before they were cool! 👌

To Interact with ProveIt

Visit the shiny and highly functional ProveIt website!

Some Semi-Technical Background

ProveIt implements proof of historical data possession on the Ethereum blockchain. What this means in practice is that any Ethereum address can submit a 32-byte cryptographic hash to ProveIt's ledger and gain the ability to prove that the owner(s) of this address wrote/possessed the text/data that resolves to the hash at a particular time. The ledger also allows addresses to stake arbitrary amounts of Ether alongside their entries, lending credibility.

Hypothetical Use Cases

Alice is a rabid Elon Musk fan, and wants to make a prediction about Musk's glorious future endeavors. Using her Ethereum address Address_Alice, Alice could submit By 2030, a company founded or owned in part by Elon Musk will have delivered a human to the surface of Mars. to the ProveIt ledger at time T. At any point from now until 2030, Alice could submit evidence of her ownership of Address_Alice in standard ways (i.e. by signing a credible message via something like the Etherscan verifySig tool), thereby proving that she made this statement at time T. This makes her seem prescient, and more importantly, affirms her Musk fanhood. One could imagine, however, that a rival Musk supporter Bob might submit many such messages, varying the year, and revealing only the one that makes him appear most credible. To combat this issue, Alice can lock up an arbitrary amount of ether, x, alongside her statement. This amount cannot be recovered without destroying the associated ledger entry. If we assume that Bob must submit 20 different entries to have a high probability of ending up with at least one very close prediction, he’s forced to lock up 20*x ether to guarantee that his revealed entry will have the same amount of credibility as Alice's, dissuading him from attacking.
Alice also moonlights as an amateur paparazza, and manages to snap an incredibly ~~compromising~~ flattering photograph of Elon at time T. She’s desperately worried that the photo will be stolen and published by Bob at T+1, depriving her of all potential proceeds. If Alice wants to be able to prove that she possessed this photo at T she could simply make a (cryptographically secure) 32-byte hash of this photograph, and store the hash in ProveIt. The data that produced this hash will of course be unknown at T, but upon Bob's release of the photo at T+1, Alice could prove her prior possession by letting anyone see that the photo hashes to the entry that she made in ProveIt at time T.
Alice's day job is as a professional economist. She runs a lot of randomized controlled trials (RCTs), and in the spirit of value-free scientific inquiry, she often wants to publicly commit herself to a particular statistical hypothesis H₀ before running an RCT to prevent ex-post p-hacking. She could of course use the American Economic Association's RCT Registry, but centralized solutions are so 2017. A better idea would be to formulate an appropriate H₀, store its hash in ProveIt, and reveal it after the RCT has concluded. In addition to the commitment mechanism, this method has the benefit of not revealing H₀ to rival economists (looking at you Bob) who might steal her idea. Of course, nothing prevents Alice from submitting many H₀ s, and only revealing the most favorable one ex-post. To combat this, verifiers should only trust Alice if she submits her hash to ProveIt, publicizes it along with her name, and associates it with her current project, all before running the RCT. This reputationally commits her to a single H₀.

Technical Notes

While building ProveIt, I realized that having set functionality would be helpful, so I implemented it in contracts/Sets.sol. It's quite efficient, with O(1) insertion, removal, and existence checks.
Contracts of interest are deployed at:

Contract	Address	Link	Network
Prover.sol	0x117ca39dffc4da6fb3af6145dfff246830637fe2 0x286e1143ab350d0238be4494da6dab9ca3662517 0x286e1143ab350d0238be4494da6dab9ca3662517	verified on Etherscan Etherscan Etherscan	Mainnet Rinkeby Ropsten
Hash.sol	0xca260ffffb0270ee07ec6892fa9d44f040454e4d 0x125bbe680d2c6665151ad8c9c89727a64683fdcb 0x125bbe680d2c6665151ad8c9c89727a64683fdcb	verified on Etherscan Etherscan Etherscan	Mainnet Rinkeby Ropsten
Sets.sol	0x48d904b3bf1cfcd7e1ce2dbcf7dcaecf0b0575c6 0x2aacb774a7214075372b52e24ff7391a4e3ea883 0x2aacb774a7214075372b52e24ff7391a4e3ea883	verified on Etherscan Etherscan Etherscan	Mainnet Rinkeby Ropsten

Tips

Accepted, not required! ETH: 0x8688a84fcFD84d8F78020d0fc0b35987cC58911f

NoahZinsmeister / ProveIt