Date: Thu, 21 Jun 2018 16:28:15 -0400
From: "Peter D. Gray" <peter@coinkite.com>
To: Jonas Schnelli <dev@jonasschnelli.ch>
Message-ID: <20180621202814.GE99379@coinkite.com>
Reply-To: Peter Gray <peter@coinkite.com>
References: <CAPg+sBhGMxXatsyCAqeboQKH8ASSFAfiXzxyXR9UrNFnah5PPw@mail.gmail.com>
	<5b6b9d44-8e6c-2799-438e-d311e221bb57@satoshilabs.com>
	<8CF4BD50-0ECE-4F96-B978-397116CD76CE@jonasschnelli.ch>
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In-Reply-To: <8CF4BD50-0ECE-4F96-B978-397116CD76CE@jonasschnelli.ch>
Organization: Coinkite Cryptobank (www.coinkite.com)
User-Agent: Mutt/1.6.0 (2016-04-01)
Cc: Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
Subject: Re: [bitcoin-dev] BIP 174 thoughts
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On Tue, Jun 19, 2018 at 05:20:34PM +0200, Jonas Schnelli wrote:
=2E..
>=20
> I don=E2=80=99t see any reasons why space would be an issue.
>=20
> HWWs probably can=E2=80=99t handle PBST natively since it is not optimise=
d for
> presenting various informations in a signing-verification.

The Coldcard hardware wallet is PSBT native and does work directly from PSB=
T.

> A single stream-in of a PSBT through USB (or similar channel) will not wo=
rk in
> many cases since HWW come often with very restrictive RAM constraints.

For the Coldcard, we expect a PSBT to be 'uploaded' over USB (can
also be provided on MicroSD card) and we work in-place with it,
scanning over it a few different times. If the user approves the
transaction, we produce a signed PSBT or final transaction and that
gets downloaded.

We support 256k byte PSBT files with hundreds of inputs/outputs
(IIRC, and exact limits still TBD) and are operating in a system
with only 25k free RAM after startup.

> Furthermore, I forget to mention in my last mail, that registering (or de=
fining)
> a mime-type for PSBT would probably a great usability feature.
> (Send PSBT by email/messanger and with dbl-click to open feature, etc.)

+1 for mimetype, especially since it's a binary format.

---
Peter D. Gray  ||  Founder, Coinkite  ||  Twitter: @dochex  ||  GPG: A3A31B=
AD 5A2A5B10


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