[DennisP]

Contracts I'm working on include variants of anti-theft vaulting, blind auctions, crowdfunding, person-to-person gambling, currencies, exchanges, and a simple implementation of Bitcoin's Lightning. None of them require external data.

For those contracts that do, at least you're reducing the third-party trust to "provide accurate data" instead of "hold my funds without stealing them." To reduce trust in a single entity you can use various schemes that allow multiple independent parties to provide the data.

[homogeneous]

> anti-theft vaulting

Can you go into more details about this?

> blind auctions

Or this? How does the contract ensure that the winner of the auction receives what they have purchased?

> crowdfunding

In what respects beyond simply collecting funds? How does the contract judge that the terms of the funding are adhered to or ensure that the crowdfunders receive whatever it is they are entitled to as funders?

> person-to-person gambling

Any examples? In my post I gave the example of betting on a sports game but this requires a trusted 3rd party to officiate the outcome of the game.

> currencies, exchanges

These are vague descriptions and these things have already been done by bitcoin.

I'm not trying to nitpick, but I'm looking for specific practical examples that demonstrates the potential utility of ethereum.

[DennisP]

So this gets into the difference between the rhetoric about smart contracts, and what they actually do. Obviously a smart contract can't ensure that an auction winner or crowdfunder gets the item. At best there could be some kind of reputation system. But to enforce something in the real world, you'd have to get an actual court involved. The smart contract removes the need to have an auctioneer running the auction and handling funds, that's all.

But that still means that, for example, when I'm trying to implement a new variant on crowdfunding, I can write the whole backend in several pages of code and just publish it, instead of renting servers, administering databases, signing up with a payment provider and having to comply with its terms of service.

An example of a vault is this scheme: http://hackingdistributed.com/2016/02/26/how-to-implement-se...

...which some researchers proposed for Bitcoin, saying it'd be "easy" to implement with a hard fork adding a new opcode. I implemented the same scheme in a smart contract and it took 20 minutes.

Sports betting needs third-party data, but casino games don't.

[homogeneous]

Thanks for the reply. I think I understand what you're getting at.

[makomk]

Stuff like blind auctions and gambling is somewhat constrained by the fact that Etherium applications have to be deterministic and their state information and transaction history has to be publicly visible.