Bindings/API for deriving a public key from a message digest and a signature

[gigabitcoin]

Bindings/API for deriving a public key from a message digest and a signature

[mikekelly]

ah. apologies, I thought it only had specific chosen bindings. I will have a look through those docs and see if I can find what I'm looking for. thanks again! :)

[mikekelly]

ok cool, interfacing with c libraries is above my swift paygrade so if you have any pointers or WIP code I can follow along with I'd really appreciate it :)

[csjones]

@mikekelly I've started a draft PR with my initial implementation here: #211

Let me know what feedback you have 😉

[mikekelly]

@csjones awesome man thanks for doing this, I'll take a look shortly

[csjones]

Hey @mikekelly 👋 Are you referring to the recovery module in secp256k1? Those binding are available and a simple unit test exists to make sure they work. You'll want to refer to the upstream documentation for what C APIs to use exactly.

The Swift APIs for the recovery module is something I'm working on currently in addition to better documentation overall using DocC.

[mikekelly]

@csjones ok thanks for the reply. Do you have a branch with this WIP on the recovery module? Be good to see how it's done :)

[csjones]

@csjones ok thanks for the reply. Do you have a branch with this WIP on the recovery module? Be good to see how it's done :)

No public branch yet, Swift API is still in flux. I'll post a PR linking back to this thread when it's alpha-ready. 😁

[mikekelly]

ok cool, in the mean time I've had a look again at the bindings in the unit test you linked to and I'm not sure that function does what I'm looking for (ie. deriving a public key from a sig and a message digest)

[csjones]

ok cool, in the mean time I've had a look again at the bindings in the unit test you linked to and I'm not sure that function does what I'm looking for (ie. deriving a public key from a sig and a message digest)

What about the upstream documentation? All of the recovery modules APIs are available through this swift package. The unit test is just a single example that demonstrates the secp256k1 C APIs work in Swift.

[csjones]

ah. apologies, I thought it only had specific chosen bindings. I will have a look through those docs and see if I can find what I'm looking for. thanks again! :)

No worries and you're welcome! Happy to help 😄

Would you mind doing me a favor and sharing what you're looking to accomplish and/or build exactly? The details will help me decide how the Swift API takes shape. Also, having a specific use case helps me test out the implementation.

[mikekelly]

Ideally, I'm looking for something like this:

let recoveredPubkey = try! secp256k1.Recovered.PublicKey(messageHash: [UInt8], signature: [UInt8])

[mikekelly]

for context: I'm hacking on a client for a cryptographic protocol and the client needs to derive the public key from a message hash and a signature (for verification purposes)

[csjones]

Ideally, I'm looking for something like this:

let recoveredPubkey = try! secp256k1.Recovered.PublicKey(messageHash: [UInt8], signature: [UInt8])

Thanks! That structure resembles what I've been narrowing in on. In terms of use-case, do you have a link to the cryptographic protocol you're referring to?

[mikekelly]

here's the specific bit of the protocol I'm working on atm:

https://github.com/coinkite/coinkite-tap-proto/blob/master/docs/protocol.md#certs

if you want to chat in more detail about what I'm working on feel free to DM me! :)

[csjones]

here's the specific bit of the protocol I'm working on atm:

https://github.com/coinkite/coinkite-tap-proto/blob/master/docs/protocol.md#certs

if you want to chat in more detail about what I'm working on feel free to DM me! :)

Dope! Super helpful and appreciate the reference. Got what I was looking for and I'm going to read up on the protocol. Thank you 😊