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Date: Wed, 21 Oct 2015 10:14:01 +0000
Message-ID: <CAAS2fgSPn9WeC+aw1OSyoRNbO3gTJTnTe6cwuOb0ydCNs95A4A@mail.gmail.com>
From: Gregory Maxwell <gmaxwell@gmail.com>
To: Christian Decker <decker.christian@gmail.com>
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Cc: Bitcoin Dev <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] [BIP] Normalized transaction IDs
Precedence: list

On Wed, Oct 21, 2015 at 8:49 AM, Christian Decker
<decker.christian@gmail.com> wrote:
> Isn't that sort of what this BIP describes as well? Except that we use the
> scriptSig to transport the signatures internally to the transactions and
> strip them when it comes to signing/checking? The wire format and transport
> of transactions do not change so old clients continue to fetch and process
> transactions as before, they just can't verify the TX. Blocks still
> reference the instance but verification uses the stripped TX with the
> signatures on the side, etc.

"sort of"

Using the sighash normalization doesn't allow creating a utxo set or
scanning the blockchain while only transferring ~1/3rd of the data
(allowing for reduced security fast start, and private lite wallets);
it requires txin ID rewriting when the witness changes on a parent
transaction; it requires hashing each transaction multiple times (for
the normalized ID, and the old ID), it requires storing two IDs for
every transaction in the UTXO set. -- but indeed, it's easier to
deploy (though not infinitely easier as I thought before).