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Author Topic: is it possible to confirm in advance? | a fraud with a slow computer  (Read 810 times)
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April 23, 2011, 08:59:59 PM

A confirmation (creating a block) is an expensive operation. However, every operation can in principle be performed by any computer. Suppose that a seller waits for 6 confirmations for a transaction T0. After the seller receives confirmations and gives goods, the buyer inserts into the network 7 prepared confirmations confirming a conflicting transaction T1, and T1 expels T0. Money disappears from seller's account.

If the buyer spends 30 days in preparing 7 confirmations and the network spends (1/6/24) days producing every confirmation, than the buyer should own only (1/6/24)/(30/7) = 1/617 part of the network -- not so much. If this fraud is possible, should not seller's behavior (how many confirmations to await) depend on the amount of transferred money?
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April 23, 2011, 09:30:30 PM

Not possible. The only way to get a confirmation is to put the transaction in a block in the longest chain. The only way to do that is to put it at the end and this requires using a bit of data from the old latest block. If you 'start early' you'll end up with a new valid version of a really old block that no one will incorporate.

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