Hello Praveen

You're absolutely right. We could refer to transactions by the hash that gets signed.

However the way that bitcoin transactions reference each other has already been established to be hash of transaction+signature. Changing this would require a hard fork.

Segwit is the realization that this could be done as a soft fork if we simply extract the signature outside of what the old client considers a transaction. And into a new transaction format where we do exactly what you're describing.

In my opinion the way it originally worked with the sig inside the transaction was simply an oversight by satoshi. No different than a bug.

Cheers
Ariel Lorenzo-Luaces


On Nov 20, 2017, 9:29 AM, at 9:29 AM, Praveen Baratam via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:
>Bitcoin Noob here. Please forgive my ignorance.
>
From what I understand, in SegWit, the transaction needs to be
>serialized
>into a data structure that is different from the current one where
>signatures are separated from the rest of the transaction data.
>
>Why change the format at all? Why cant we just compute the Transaction
>ID
>the same way the hash for signing the transaction is computed?
>
>--
>Dr. Praveen Baratam
>
>about.me <http://about.me/praveen.baratam>
>
>
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