Add message signing

[filiplipa]

Problem

It seems that message signing hasn't been exposed yet in Kotlin.

Description

It would be useful to have this option to sign messages using private keys.

Alternatives

No response

[notmandatory]

Are you looking to sign an arbitrary text message with some private key from your wallet descriptor? and then you'll also need a way to verify the signature with the corresponding public key right? I don't think we have any example for how to do this with bdk, but it should be possible.

If anyone wants to write up a an example in Rust for how to sign messages with a DescriptorSecretKey and verify them with a DescriptorPublicKey that would be helpful.

[q-src]

Please see also #139

[thunderbiscuit]

Related to bitcoindevkit/bdk#601. Once the feature is available in Rust BDK we'll expose it to the bindings.

[notmandatory]

Moved issue to bdk-ffi and will resolve once feature is added.

[thunderbiscuit]

Note: the correct way to apply general-purpose message signing is likely to be by implementing BIP-322.

[thunderbiscuit]

I'm closing this because it's a feature request that belongs at the Rust level of BDK. Once we get it in we'll happily expose it in the bindings!