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?

4 Answers 4


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.

  • Has any consensus been made? Who are those developers (so I can follow their responses in more detail) Commented Dec 6, 2012 at 7:41

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.

  • Granted, but what if there was something important that we haven't thought of yet. Could it happen with the current block chain or would we need to start again?
    – billpg
    Commented Sep 16, 2011 at 17:25
  • Sure, you would just have to have quite a bit of planning, and get the mining pools to agree to it. For most things it seems like a third-party service or something at the client level would be best, somethings would prob be pushed to a bitcoin fork, but there is no inherent reason why changes couldn't be made to the data the bitcoin block chain stores given enough consensus and lead time Commented Sep 16, 2011 at 19:02

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.


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.

  • A soft fork does not make two chains, it's by definition a backwards compatible change.
    – Claris
    Commented May 4, 2017 at 13:03
  • Very true but I have mentioned of Soft fork behaving as a connected branch rather than non backward compatible branch.
    – mannutech
    Commented May 15, 2017 at 10:29

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