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Date: Fri, 23 Jan 2015 16:52:28 +0000
Message-ID: <CAAS2fgSKBS9zCQqp+hJUF2Ro8LNw4s0=J08M=76sOJmNfpLptQ@mail.gmail.com>
From: Gregory Maxwell <gmaxwell@gmail.com>
To: slush <slush@centrum.cz>
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Cc: Bitcoin Development <bitcoin-development@lists.sourceforge.net>
Subject: Re: [Bitcoin-development] SIGHASH_WITHINPUTVALUE
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On Fri, Jan 23, 2015 at 4:18 PM, slush <slush@centrum.cz> wrote:
> Can you send me any reference about this? Of course if that solves the
> problem, hard fork would not be necessary anymore. I'm just not aware of
> any.

Sure; will aggregate up the citations when I'm not travling later today.

> To sign transaction with hundreds of inputs on device with limited memory
> capabilities, I need to stream all previous transactions into device, for
> every signed input.
>
> That means roughly 200^2 transaction verifications for 200 inputs to sign.
> Very slow, but does not limit the device for any particular size of signed
> transaction.

I'm not sure where the ^2 is coming from.  So what I'd understand that
you'd do is stream in the input txid:vouts which you spend, then you'd
stream the actual inputs which would just be hashed and value
extracted (but no other verification), and you'd build a table of
txid:vout->value, then the actual transaction to be signed.

This should have O(inputs) hashing and communications overhead. Is
there a step I'm missing?