From: Johnson Lau <jl2012@xbt•hk>
To: Aymeric Vitte <vitteaymeric@gmail•com>
Cc: bitcoin-dev <bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Two questions about segwit implementation
Date: Mon, 27 May 2019 01:24:13 +0800 [thread overview]
Message-ID: <DD2C67C8-0DF6-4140-8427-19B7F28FA22C@xbt.hk> (raw)
In-Reply-To: <a7742e04-22b1-2015-440a-ef81b5fbeed4@gmail.com>
Empty scriptSig doesn’t imply segwit input: if the previous scriptPubKey is OP_1 (which does not allow witness), it could still be spent with an empty scriptSig
Similarly, a scriptSig looking like a spend of P2SH-segwit doesn’t imply segwit input: if the previous scriptPubKey is empty, it could be spent with a push of any non-zero value.
> On 27 May 2019, at 1:09 AM, Aymeric Vitte <vitteaymeric@gmail•com> wrote:
>
> I did not phrase correctly in fact, what I meant is: if the validator
> sees empty or witness script in scriptSig, then this is a segwit input,
> and doing this one by one the validator can associate the correct segwit
> data to the correct segwit input, so 00 does not look to be needed
>
> Le 26/05/2019 à 18:28, Johnson Lau a écrit :
>> This is not how it works. While the transaction creator may know which inputs are segwit, the validators have no way to tell until they look up the UTXO set.
>>
>> In a transaction, all information about an input the validators have is the 36-byte outpoint (txid + index). Just by looking at the outpoint, there is no way to tell whether it is segwit-enabled or not. So there needs to be a way to tell the validator that “the witness for this input is empty”, and it is the “00”.
>>
>>> On 27 May 2019, at 12:18 AM, Aymeric Vitte <vitteaymeric@gmail•com> wrote:
>>>
>>> ……. for the 00 number of witness
>>> data for non segwit inputs the one that is doing the transaction knows
>>> which inputs are segwit or not, then parsing the transaction you can
>>> associate the correct input to the correct witness data, without the
>>> need of 00, so I must be missing the use case
>>
next prev parent reply other threads:[~2019-05-26 17:24 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-25 23:56 Aymeric Vitte
2019-05-26 14:33 ` Johnson Lau
2019-05-26 16:18 ` Aymeric Vitte
2019-05-26 16:28 ` Johnson Lau
2019-05-26 17:09 ` Aymeric Vitte
2019-05-26 17:24 ` Johnson Lau [this message]
2019-05-26 21:17 ` Aymeric Vitte
2019-05-26 17:54 ` Pieter Wuille
2019-05-26 19:34 ` Thomas Kerin
2019-05-27 7:26 ` Kostas Karasavvas
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