Hey, I've written on my idea how to make contracts with people who don't really know each other with low cost, no third party.
Ideas based on NashX.com service. Special thanks to Mike Hearn for "Contracts" page on the wiki.
http://blog.oleganza.com/post/58240549599/contracts-without-trust-and-without-a-third-partyTLDR:
1. Two parties independently lock some amount of money in a single Bitcoin transaction without meeting in person or trusting anyone.
2. This money can be unlocked only when both agree with that. If at least one party does not want to unlock the deposit, another party cannot do anything about it.
3. Both parties can unlock deposit only atomically, for both of them. No one can unlock just for himself.
4. No one else has access to the deposits and neither party can access other party’s money.
Output scripts:
txout1: AlicePubkey CHECKSIGVERIFY SHA256 HashA EQUALVERIFY SHA256 HashB EQUALVERIFY
txout2: BobPubkey CHECKSIGVERIFY SHA256 HashA EQUALVERIFY SHA256 HashB EQUALVERIFY
HashA, HashB are hashes of the secret numbers of each participant. Numbers are revealed when they want to unlock the money.
Amount of deposit should be 200-300% of the price. E.g. if the deal is about 1 BTC worth of merchandise, the deposit should be at least 2 BTC.
NashX ask seller for smaller deposit (100%) because he sends first, but this doesn't seem "fair" for many people. So lets have 300% each, so it does not really matter who sends first. Parties can negotiate how much they lock up, of course.
Ideas?