Re: [bitcoin-dev] BIP Number Request: Addresses over Audio

From: Thomas Daede <bztdlinux@gmail•com>
To: bitcoin-dev@lists•linuxfoundation.org
Subject: Re: [bitcoin-dev] BIP Number Request: Addresses over Audio
Date: Tue, 9 Aug 2016 18:09:50 -0700	[thread overview]
Message-ID: <aa41549b-b392-a225-26e1-2dcf4edfeb21@gmail.com> (raw)
In-Reply-To: <CAL9WuQXsbBJ0UwdS+o=UqJCcsebcPa9Ug5A=uNtc6Z+9CNEFPg@mail.gmail.com>

If this is just encoding BIP-21 addresses, it is basically an "audio QR
code". In this case, does publishing it as a BIP still make sense? (Not
to imply that it doesn't, but it's something you should consider.)

Please look at existing implementations of audio modems when creating
your design. A lot of this work has been done many times before, so
there is a lot to learn from.

Your selected frequencies are harmonics of each other, meaning nonlinear
distortion will make detection more difficult. The Bell 202 and similar
modem standards chose AFSK frequencies to minimize interference.

Repeating a message multiple times is a very inefficient method of error
recovery. It works, but there may be better techniques, such as trellis
modulation or other convolutional codes.

Defining channel models to simulate your various use cases will help a
lot to determine if you have met your requirements.

- Thomas

P.S. I also briefly considered audio to exchange transactions with a
hardware wallet. Using GNU Radio made the implementation much easier.

On 08/09/2016 04:06 PM, Daniel Hoffman via bitcoin-dev wrote:
> I have updated the GitHub a lot (changed tones to be less chirpy, fixed
> some smalls) and made a couple of samples (see attachment for MP3 and
> FLAC of both tone tables, first 16 then 4). Is this good enough to
> warrant an official BIP number? I haven't built a decoder yet, but it
> seems like the encoder is working properly (looked at Audacity, seems
> like it is working), and some people on reddit want to "allow for
> decoding experiments"
> <https://www.reddit.com/r/btc/comments/4wsn7v/bip_proposal_addresses_over_audio_thoughts/d69m3st>
> 
> What suggestions do you all have for it?
> 
> On Mon, Aug 8, 2016 at 8:50 PM, Daniel Hoffman
> <danielhoffman699@gmail•com <mailto:danielhoffman699@gmail•com>> wrote:
> 
>     It wouldn't be feasible in the vast majority of cases, but I can't
>     think of a reason why it can't be built into the standard.
> 
>     On Mon, Aug 8, 2016 at 5:59 PM, Trevin Hofmann via bitcoin-dev
>     <bitcoin-dev@lists•linuxfoundation.org
>     <mailto:bitcoin-dev@lists•linuxfoundation.org>> wrote:
> 
>         Would it be feasible to transmit an entire BIP21 URI as audio?
>         If you were to encode any extra information (such as amount), it
>         would be useful to include a checksum for the entire message.
>         This checksum could possibly be used instead of the checksum in
>         the address.
> 
>         Trevin
> 
> 
>         On Aug 8, 2016 3:06 PM, "Justin Newton via bitcoin-dev"
>         <bitcoin-dev@lists•linuxfoundation.org
>         <mailto:bitcoin-dev@lists•linuxfoundation.org>> wrote:
> 
>             Daniel,
>                Thanks for proposing this.  I think this could have some
>             useful use cases as you state.  I was wondering what you
>             would think to adding some additional tones to optionally
>             denote an amount (in satoshis?).
> 
>             (FYI, actual link is here:  https://github.com/Dako300/BIP
>             <https://github.com/Dako300/BIP> )
> 
>             Justin
> 
>             On Mon, Aug 8, 2016 at 2:22 PM, Daniel Hoffman via
>             bitcoin-dev <bitcoin-dev@lists•linuxfoundation.org
>             <mailto:bitcoin-dev@lists•linuxfoundation.org>> wrote:
> 
>                 This is my BIP idea: a fast, robust, and standardized
>                 for representing Bitcoin addresses over audio. It takes
>                 the binary representation of the Bitcoin address (little
>                 endian), chops that up into 4 or 2 bit chunks (depending
>                 on type, 2 bit only for low quality audio like american
>                 telephone lines), and generates a tone based upon that
>                 value. This started because I wanted an easy way to
>                 donate to podcasts that I listen to, and having a
>                 Shazam-esque app (or a media player with this
>                 capability) that gives me an address automatically would
>                 be wonderful for both the consumer and producer. Comes
>                 with error correction built into the protocol
> 
>                 You can see the full specification of the BIP on my
>                 GitHub page (https://github.com/Dako300/BIP-0153
>                 <https://github.com/Dako300/BIP-0153>).
> 
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> 
> 
> 
> 
>             -- 
> 
>             Justin W. Newton
>             Founder/CEO
>             Netki, Inc.
> 
>             justin@netki•com <mailto:justin@netki•com>
>             +1.818.261.4248 <tel:+1.818.261.4248>
> 
> 
> 
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