Quote from: infinitybo on December 29, 2013, 04:15:28 PM

Yes you have the possibility to use this option furthermore they allow you the ability to create low-trust contracts.

I'm sorry - did you read my question? I'm not asking whether or not these kinds of contracts are possible. I AM asking this: what prevents someone from spending the bitcoin included in a partially-fulfilled contract before it's broadcast and verified on the network?

If nothing is in place to prevent the sender from spending the bitcoin before the contract is broadcast, then that seems to REALLY limit the usefulness of these contracts.

To quote the wiki:

Quote

[The old man] creates a transaction with a lock time of the grandson's 18th birthday that pays the coins to another key owned by the grandson, signs it, and gives it to him - but does not broadcast it. This takes care of the 18th birthday condition. If the date passes, the grandson broadcasts the transaction and claims the coins.

If I'm the grandson, what assurance do I have that by the time my 18th birthday rolls around, those coins will not have already been spent?