As a side note, you may be interested about the 2D-Doc, which is a new French standard used to protect documents such as address proofs or invoice. I've been involved with it closely at work.

Every 2d-Doc include an ECDSA signature inside a 2D barcode, the key being that the barcode is a Datamatrix and not a QR code.

If any of you can read French, the technical specification of the standard can be found here :: https://ants.gouv.fr/content/download/516/5665/version/4/file/ANTS_2D-Doc_CABSpec_v2.0.1_erratum.pdf

Basically, a short summary of the protected document is encoded inside the barcode, followed by an ECDSA signature of the summary (still in the barcode). The signature is done by an official, government-approved 2D-Doc emitter. The 2D-Code contains a short reference (a few bytes) to designate which emitter signed it, and then you can lookup the 2D-Doc TSL supplied by the French government to get all the X509 Certificates from every emitters you are interested in, in order to check the signature.

While 2D-Doc solve a very different problem than Bitcoin + BIP70, you may be interested in knowing about it as hundred of thousands of them have been emitted successfully while solving one of the problem you face : embedding an ECDSA signature inside a 2D barcode.

Thank you for your time,

Clément Elbaz

Le mar. 21 juil. 2015 à 10:20, Andreas Schildbach via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> a écrit :
Hmm, the advanced QR code standards are perhaps even useful if we don't
change anything about BIP7x. Because if we can cram more data without
loosing scanning performance this maybe means also we can stay with the
data we have but improve scanning?


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