Erasure coding

[burdges]

We've discussed using erasure codes in novasamatech/parity-signer#457 and novasamatech/parity-signer#320 (comment) probably a rateless code like Raptorq although one should work out the overhead.

And TXQR maybe works https://hub.packtpub.com/introducing-txqr-data-transfer-via-animated-qr-codes/ ref. https://github.com/w3f/research-internal/issues/143

If we used erasure codes then we'd simply stream QR codes until the decoder captured them all, but actually cameras can take so long to capture a dense QR code that this might prove tricky. I'd think one wants a protocol bespoke to streaming video honestly, so like QR codes but maybe lower resolution and faster.

[burdges]

novasamatech/parity-signer#457
novasamatech/parity-signer#791

[Slesarew]

Note that uos protocol is pretty much wrapped in Raptor, as sketched in #8. Don't just merge that though, the actual implemented uos protocol does not really match neither the master here nor what I sketched in PR, by now we actually need a proper analysis to figure out what barnacles have grown on this ship. I'll certainly do it myself once the core Signer is more or less finalized.