4 ms·

B would need to refer to a transaction output that has at least 1 BTC to be able to sign a transaction sending 1 BTC to B. Until A's transaction is included in

• rpearl 8y ago
  > Until A's transaction is included in a block, B can not do that. This is just not true at all? for B to refer to A, it needs to know the transaction id. Transaction ids are sha256(sha256(raw_transaction)) and a raw transaction consists of inputs and outputs. All this is known before the transaction gets put in a block--and has nothing to do with blocks. Blocks and mining mitigate against double spending (...by burning an insanely huge amount of energy to do so, inefficiently. But that's a separate issue, at least right here)
  • drdrey 8y ago
    But is it valid to refer to a transaction hash that only exists in the mempool? The transaction you refer to has to exist in history, which means it has to live on the longest chain, no?