Quote from: gmaxwell on July 19, 2017, 03:56:30 PM

There are many problems because people do more with unconfirmed transactions then send them and wait for them to confirm before doing anything else.

Why it's problem?
I send transaction 1 from address 2. So, before transaction will be confirmed (or deleted from mempool) i can't do anything with this address (except my wallet has opportunity to spend unconfirmed change). But i can to use another addresses.
Problem could happen only if i try to spend outputs of transaction 1 while it uncofirmed.

Quote from: gmaxwell on July 19, 2017, 03:56:30 PM

For example, you may want to spend the change resulting from an unconfined transaction-- so that the rest of your coins are not held hostage until the next block-- but if the transaction ID is changed the child transactions are invalidated. You couldn't even reissue the replacement until you come back online and learn the new ID, and then imagine that the private keys are kept offline in a safe.

Yes, i know about it. But in new wallets like Electrum or blockchain info it isn't a problem. After confirmation wallet will show new TXID.

Quote from: gmaxwell on July 19, 2017, 03:56:30 PM

If you make only the most boring kinds of transactions, never deal with anything unconfirmed (including making more payments until confirmation, or replacing transactions) and use carefully and competently written wallet software then malleability is at worst a minor nuisance. If you are trying to do anything fancy with smart contracts, unconfirmed transactions (including just chaining them), or are _writing_ wallet software that has to handle malleation happening, then it's a burden and footgun.

CLTV and CSV were introduced to recover some of the worst of the damage done by malleability-- without them you couldn't safely do multiparty escrows with timeouts... but even with them the fact that malleation invalidates subsequent spends makes life hard in many ways.

Of course i talk about bitcoin, not Ethereum network and smart contracts 'cause i know too few about them

Thank you for information.

Quote from: gmaxwell on July 19, 2017, 03:56:30 PM

You can also think of it as changing the outputs: an output is a txid, index, scriptPubkey, and an amount. The malleation doesn't change the index, pubkey, or amount... but it does change the txid of the output; and this is precisely the problem that segwit solves.

I know it, but changed TXID it's not a big problem for people who have patience and some technical skills Wink