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Im NOT a dev or do i know about coding this is just a idea i had in mind

I had this idea about a scam proof application that can be used for trading coins.
The app should work like this ;
User 1 wants to buy lets say LT from user 2 and pay with bitcoins.
They both start up the application and enter the amount they both agreed with and hit send. The transaction will stay pending till both have enter the same amount they agreed on if not the transaction expires after a certain amount of time. 

Sample
User1 wants to buy 10LT from user2 and wants to pay with Bitcoins. User one starts up the app and enters the amount off LT hes going to buy and the amount of bitcoins hes going to pay. User2 starts up his app and enters the amount of LT hes going to sell and the amount of bitcoins hes going to receive.  Both hit send for the trading to take place and if both amounts they agreed on match the trade takes place if not it expires (within a certain time frame).


Would this be possible? Any thoughts?

(My english is not perfect sorry)

good idea, i think the main problem would be people trying to hack the app

That must involve some form of escrow or contracts. Between different alt-coins this is difficult to implement without a third party... Even if both users sign and send between them a transaction with a lock-time set some "minutes"?! in the future, check that all is OK within the time frame, and if not, broadcast immediately a transaction which consume the same input and send it to one-self... But that can hardly prevent both users to screw up the trade. So it's not impossible but not without a third party...

If I'm understanding correctly, you are proposing a protocol with security based on the assumption that no one will use a modified version of your client. This is not how software works; if it were, the blockchain itself would be a lot of unnecessary work.


maxuser, there actually is a trustless way to trade across chains without the use of the third party; it's pretty clever. See the wiki entry: https://en.bitcoin.it/wiki/Atomic_cross-chain_trading (https://en.bitcoin.it/wiki/Atomic_cross-chain_trading)

Thanks! I have take look at this and it can apply to this but even with a short lock time there are some serious drawbacks like mentioned in the wiki article to be used for "efficient" trading... I mean that issuing transactions just for the refund case when dealing with malicious users incur useless txfees for no completed trade at the end. On the other hand using/implementing a specialized altchain for inter-coins trading can be a solution but it's beyond the scope of a single app...