Can new types of transactions be included the current block chain?

Question

I was putting an answer for this question together when I realised my idea would require a new type of transaction to be invented and included in blocks.

Then I wondered how that could work. There are many mining rigs out there which would have no way of validating my transaction type.

Even if some miners do recognise my transaction and even included it in a winning block, all the other miners would not accept that winning block and instead continue mining on the previous block.

What would happen if we wanted to devlop Bitcoin this way? Would we instead have to establish Bitcoin2 with a new block chain?

Answer 1

Miners will accept block with transactions they don't understand, so long as the transactions don't attempt to create Bitcoins out of thin air. They won't include transactions they can't validate in their own mined blocks though.

There is active effort at the top levels of the Bitcoin developers to get new transaction types into the client. M-of-N transactions (transactions that require a set of signatures), for example, are close to obtaining a consensus.

Answer 2

Short answer:

Technically possible? Yes. Likely? No.

It would be possible to modify the protocol to include other types of transactions -- such things have been proposed for a wide variety of issues, including being able to lockdown stolen coins, timestamp messages, etc.

It is highly unlikely they will ever make it in, at least not anytime soon, because changing the blockchain is a Big Deal and we are already dealing with "block chain bloat" and many of them have other possible solutions that don't involve modifying the block chain.

Your particular suggestion (in the other thread) seems incredibly unlikely to ever make it as part of the protocol since there is just no need for it to be. Trading exchanges can easily implement futures, options, and all sorts of derivatives if they want - no changes to blockchain necessary.

Answer 3

The key issue here is opcodes. If your transaction does not require any new script opcodes, you should be able to create these and have them make it into the block chain without any trouble (they won't get relayed because they won't pass the isStandard check, Eligius mining pool, for one, will relay non-standard transactions. Any miner will /accept/ them into their block, they just won't relay them which makes it harder for your transaction to propagate.

But the key is, if you don't need any new opcodes, this does not require any changes to the core bitcoin in order to work.

Answer 4

Actually if you jump into Bitcoin as being an implementation of Blockchain, and new transactions leading to a Blockchain 2 is possible which is actually known as a fork (can be soft or hard fork).

The case which you are telling about is Soft fork as in case of Bitcoin network, which literally creates a new branch of transactions on a running chain and the point from where the new branch emerges accept the new kind of transactions being made. But they cannot bypass the basic fact of creating bitcoin out of thin air.

When a hardfork occurs, it renders the new transaction being seen as useless and Infact can be taken as a new coin/blockchain/alternate coin.