Enable module recovery by default

[MavenRain]

This is required for building libbitcoin independently, but is currently disabled by default. Turning this default on will provide a better customer experience for developers attempting to quickly building their bitcoin development environment.

[BernardoDeLaPlaz]

Agreed. This would be a good change.

[apoelstra]

Closing this. People should not use recoverable signatures in basically any application -- their patent story is questionable and they cannot be batch-validated.

[dcousens]

@apoelstra doesn't bitcoind use it?

[apoelstra]

Yes, but only for historical reasons, in the signmessage API which will be replaced by BIP322 or something similar.

[apoelstra]

I understand that it may be necessary for Bitcoin-related projects such as libbitcoin. However we still want to ensure that people using the module know they are using something odd.

[dcousens]

Maybe note that in the README?

[dcousens]

@evoskuil what is your thoughts around this?

[dcousens]

@apoelstra after a quick search, this doesn't seem to be a new thought https://bitcointalk.org/index.php?topic=940436.msg10306479#msg10306479 https://bitcoin.stackexchange.com/questions/75322/why-do-we-need-public-key-as-part-of-witness-in-p2wpkh-transactions

Has anyone determined if it is actually a problem? It seems to be guesses at this point.

@laanwj what about bitcoind? Is it non-issue if the wallet support isn't compiled in?

Why not simply remove it?

[evoskuil]

Libbitcoin uses it to implement the message signing “standard” as an API and command line utility in bx. It doesn’t matter to us whether it’s enabled by default or otherwise - if it remains conditional we have to deal with it missing. More significantly we’ve always had to deal with lack of versioning on the library itself.

[dcousens]

@evoskuil what about the patent story?

[evoskuil]

no opinion