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Merge pull request #827 from rating89us/patch-44

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ch07: introduce "pure segwit transaction" term
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Will Binns 2021-03-04 19:39:09 +01:00 committed by GitHub
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@ -998,13 +998,13 @@ Before segwit, transactions could have their signatures subtly modified by third
With the introduction of Segregated Witness, transactions have two identifiers, +txid+ and +wtxid+. The traditional transaction ID +txid+ is the double-SHA256 hash of the serialized transaction, without the witness data. A transaction +wtxid+ is the double-SHA256 hash of the new serialization format of the transaction with witness data.
The traditional +txid+ is calculated in exactly the same way as with a nonsegwit transaction. However, since the segwit transaction has empty ++scriptSig++s in every input, there is no part of the transaction that can be modified by a third party. Therefore, in a segwit transaction, the +txid+ is immutable by a third party, even when the transaction is unconfirmed.
The traditional +txid+ is calculated in exactly the same way as with a nonsegwit transaction. However, since a pure segwit transaction (a transaction that only contains segwit inputs) has empty ++scriptSig++s in every input, there is no part of the transaction that can be modified by a third party. Therefore, in a pure segwit transaction, the +txid+ is immutable by a third party, even when the transaction is unconfirmed.
The +wtxid+ is like an "extended" ID, in that the hash also incorporates the witness data. If a transaction is transmitted without witness data, then the +wtxid+ and +txid+ are identical. Note that since the +wtxid+ includes witness data (signatures) and since witness data may be malleable, the +wtxid+ should be considered malleable until the transaction is confirmed. Only the +txid+ of a segwit transaction can be considered immutable by third parties and only if _all_ the inputs of the transaction are segwit inputs.
The +wtxid+ is like an "extended" ID, in that the hash also incorporates the witness data. If a transaction is transmitted without witness data, then the +wtxid+ and +txid+ are identical. Note that since the +wtxid+ includes witness data (signatures) and since witness data may be malleable, the +wtxid+ should be considered malleable until the transaction is confirmed. Only the +txid+ of a pure segwit transaction can be considered immutable by third parties.
[TIP]
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Segregated Witness transactions have two IDs: +txid+ and +wtxid+. The +txid+ is the hash of the transaction without the witness data and the +wtxid+ is the hash inclusive of witness data. The +txid+ of a transaction where all inputs are segwit inputs is not susceptible to third-party transaction malleability.
Segregated Witness transactions have two IDs: +txid+ and +wtxid+. The +txid+ is the hash of the transaction without the witness data and the +wtxid+ is the hash inclusive of witness data. Only pure segwit transactions (transactions that only contain segwit inputs) have a +txid+ that is not susceptible to third-party transaction malleability.
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==== Segregated Witness' New Signing Algorithm