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From: Christopher Allen <ChristopherA@lifewithalacrity.com>
Date: Fri, 1 Jul 2022 10:37:57 -0700
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To: Alfred Hodler <alfred_hodler@protonmail.com>, 
 Bitcoin Protocol Discussion <bitcoin-dev@lists.linuxfoundation.org>
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Subject: Re: [bitcoin-dev] [BIP proposal] Private Payments
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On Fri, Jul 1, 2022 at 5:43 AM Alfred Hodler via bitcoin-dev <
bitcoin-dev@lists.linuxfoundation.org> wrote:

> I agree with your proposal to use bech32 instead of base58. It looks soun=
d
> to me and as you said, the standard would benefit from more compact QR
> codes.


The most important thing to get more compact QR codes is to not use
lowercase letters, and certain other characters, as if you can avoid them
the QRs will auto-compress.

It happens that the core of bech32 works if all caps, and you are careful
with the human readable portion.

See
https://github.com/BlockchainCommons/Research/blob/master/papers/bcr-2020-0=
03-uri-binary-compatibility.md
for more details, but a big offender is base64 which not only doesn=E2=80=
=99t
auto-compress but also can trigger binary mode that almost doubled the size
of the QR.

We have a number of standards & libraries focused on bitcoin QRs, including
support of animated QRs for things like PSBTs, but if you care about QR
size you should take a look at the techniques we use our swift library
https://github.com/BlockchainCommons/QRCodeGenerator which are also in
https://www.nayuki.io/page/qr-code-generator-library.

Basically both of these libraries support =E2=80=9Coptimal encoding using s=
egments=E2=80=9D
that if they encounter a set of characters that must be encoded in binary
(In particularly $ % * + / :) that would in most default platform QR
implementations  cause the entire QR to double in size. Instead will only
encode the small segment as binary, letting the rest of the QR leverage
auto-compression.

If your are interested in our other Airgap QR and TorGap UR efforts, see
our video from last year:
https://youtu.be/RYgOFSdUqWY We have much more on the way, including NFC
encrypted Airgap & crypto-request/response flows.

I=E2=80=99d love to see proposals for various payment and invoice QRs that =
leverage
these wallet interoperability standards we have been offering. Let us know
if you are interested, or join discussions at
https://github.com/BlockchainCommons/Airgapped-Wallet-Community

=E2=80=94 Christopher Allen, Blockchain Commons

>

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<div>On Fri, Jul 1, 2022 at 5:43 AM Alfred Hodler via bitcoin-dev &lt;<a hr=
ef=3D"mailto:bitcoin-dev@lists.linuxfoundation.org">bitcoin-dev@lists.linux=
foundation.org</a>&gt; wrote:<br></div><div><div class=3D"gmail_quote"><blo=
ckquote class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left=
-width:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(2=
04,204,204)" dir=3D"auto">I agree with your proposal to use bech32 instead =
of base58. It looks sound to me and as you said, the standard would benefit=
 from more compact QR codes.</blockquote><div dir=3D"auto"><br></div><div d=
ir=3D"auto">The most important thing to get more compact QR codes is to not=
 use lowercase letters, and certain other characters, as if you can avoid t=
hem the QRs will auto-compress.</div><div dir=3D"auto"><br></div><div dir=
=3D"auto">It happens that the core of bech32 works if all caps, and you are=
 careful with the human readable portion.</div><div dir=3D"auto"><br></div>=
<div dir=3D"auto"><div dir=3D"auto">See <a href=3D"https://github.com/Block=
chainCommons/Research/blob/master/papers/bcr-2020-003-uri-binary-compatibil=
ity.md">https://github.com/BlockchainCommons/Research/blob/master/papers/bc=
r-2020-003-uri-binary-compatibility.md</a> for more details, but a big offe=
nder is base64 which not only doesn=E2=80=99t auto-compress but also can tr=
igger binary mode that almost doubled the size of the QR.</div><div dir=3D"=
auto"><br></div><div dir=3D"auto">We have a number of standards &amp; libra=
ries focused on bitcoin QRs, including support of animated QRs for things l=
ike PSBTs, but if you care about QR size you should take a look at the tech=
niques we use our swift library=C2=A0<div dir=3D"auto"><a href=3D"https://g=
ithub.com/BlockchainCommons/QRCodeGenerator">https://github.com/BlockchainC=
ommons/QRCodeGenerator</a> which are also in =C2=A0<div dir=3D"auto"><a hre=
f=3D"https://www.nayuki.io/page/qr-code-generator-library">https://www.nayu=
ki.io/page/qr-code-generator-library</a>.=C2=A0</div><div dir=3D"auto"><br>=
</div><div dir=3D"auto">Basically both of these libraries support =E2=80=9C=
optimal encoding using segments=E2=80=9D that if they encounter a set of ch=
aracters that must be encoded in binary (In particularly $ % * + / :) that =
would in most default platform QR implementations =C2=A0cause the entire QR=
 to double in size. Instead will only encode the small segment as binary, l=
etting the rest of the QR leverage auto-compression.</div><div dir=3D"auto"=
><br></div><div dir=3D"auto">If your are interested in our other Airgap QR =
and TorGap UR efforts, see our video from last year:=C2=A0<div><div dir=3D"=
auto"><a href=3D"https://youtu.be/RYgOFSdUqWY">https://youtu.be/RYgOFSdUqWY=
</a> We have much more on the way, including NFC encrypted Airgap &amp; cry=
pto-request/response flows.=C2=A0</div><div dir=3D"auto"><br></div><div dir=
=3D"auto">I=E2=80=99d love to see proposals for various payment and invoice=
 QRs that leverage these wallet interoperability standards we have been off=
ering. Let us know if you are interested, or join discussions at=C2=A0<div>=
<a href=3D"https://github.com/BlockchainCommons/Airgapped-Wallet-Community"=
>https://github.com/BlockchainCommons/Airgapped-Wallet-Community</a></div><=
/div><div dir=3D"auto"><br></div><div dir=3D"auto">=E2=80=94 Christopher Al=
len, Blockchain Commons=C2=A0</div></div></div></div></div></div><blockquot=
e class=3D"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left-width=
:1px;border-left-style:solid;padding-left:1ex;border-left-color:rgb(204,204=
,204)" dir=3D"auto"></blockquote></div></div>

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