Subject: Re: [Bitcoin-development] 75%/95% threshold for transaction versions

From: s7r <[email-masked]>
Date: Thu, 16 Apr 2015 19:12:35 +0300

Hi Pieter,

Thanks for your reply. I agree. Allen has a good point in the previous
email too, so the suggestion might not fix anything and complicate things.

The problem I am trying to solve is making all transactions
non-malleable by default. I guess there is a very good reason why BIP62
will not touch v1 anyway.

I am trying to build a bitcoin contract which will relay on 3 things:
- coinjoin / txes with inputs from multiple users which are signed by
all users after they are merged together (every user is sure his coins
will not be spent without the other users to spend anything, as per
agreed contract);
- pre-signed txes with nLockTime 'n' weeks. These txes will be signed
before the inputs being spent are broadcasted/confirmed, using the txid
provided by the user before broadcasting it. Malleability hurts here.
- P2SH

In simple terms, how malleable transactions really are in the network at
this moment? Who can alter a txid without invalidating the tx? Just the
parties who sign it? The miners? Anyone in the network? This is a little
bit unclear to me.

Another thing I would like to confirm, the 3 pieces of the bitcoin
protocol mentioned above will be supported in _any_ future transaction
version or block version, regardless what changes are made or features
added to bitcoin core? The contract needs to be built and left unchanged
for a very very long period of time...

On 4/16/2015 8:22 AM, Pieter Wuille wrote:
> 
> On Apr 16, 2015 1:46 AM, "s7r" <[email-masked] <mailto:[email-masked]>>
> wrote:
>> but for transaction versions? In simple terms, if > 75% from all the
>> transactions in the latest 1000 blocks are version 'n', mark all
>> previous transaction versions as non-standard and if > 95% from all the
>> transactions in the latest 1000 blocks are version 'n' mark all previous
>> transaction versions as invalid.
> 
> What problem are you trying to solve?
> 
> The reason why BIP62 (as specified, it is just a draft) does not make v1
> transactions invalid is because it is opt-in. The creator of a
> transaction needs to agree to protect it from malleability, and this
> subjects him to extra rules in the creation.
> 
> Forcing v3 transactions would require every piece of wallet software to
> be changed.
> 
> -- 
> Pieter
>