expose recover() function

[motorina0]

• bitcoin-message lib is using secp256k1.recover()
• this function is not exposed by tiny-secp256k1

Related discussion: bitcoinjs/ecpair#3 (comment)

 function verify (message,...
    ...
    const publicKey = secp256k1.recover(
      hash,
      parsed.signature,
      parsed.recovery,
      parsed.compressed
    )

[junderw]

I remember back when tiny-secp256k1 first started, bitcoin-message was brought up.

The reality is: the message signing from Bitcoin Core early versions was never standardized. Many wallets have incompatible methods that are slightly similar, especially in dealing with the various address types. (back then, there was only one address type and the only variance was compressed or not.)

To be honest... bitcoin-message should be archived. At this point any "updates" to it would be meaningless back-end optimizations and arguing minutiae about why we should adopt format X over format Y or how we could make it backwards compatible with format Z (where X Y Z are all different wallet apps that put their own spin on message signing)

Adding recovery just to fill a need for bitcoin-message is not a good reason enough imo.

[junderw]

It could be useful for BOLT11 and various Lightning usecases though.

[motorina0]

I am trying to have a look at this, but I get a compilation error when running make. It's my first time using Rust.

• in lib.rs I've added secp256k1_ecdsa_recover to use secp256k1_sys::{...
• run make (using the Docker image):

for f in ./lib/cjs/*.cjs; do sed -i -e 's/\(require(".*\)\.js");/\1.cjs");/g' -- "$f"; done
RUSTFLAGS="-C link-args=-zstack-size=655360" cargo build --target wasm32-unknown-unknown --release
    Updating git repository `https://github.com/rust-bitcoin/rust-secp256k1`
    Updating crates.io index
  Downloaded cc v1.0.71
  Downloaded 1 crate (57.5 KB) in 1.29s
   Compiling secp256k1-wasm v0.0.0 (/tiny-secp256k1)
error[E0432]: unresolved import `secp256k1_sys::secp256k1_ecdsa_recover`
  --> src/lib.rs:19:36
   |
19 |     secp256k1_ec_seckey_tweak_add, secp256k1_ecdsa_recover, secp256k1_ecdsa_sign,
   |                                    ^^^^^^^^^^^^^^^^^^^^^^^
   |                                    |
   |                                    no `secp256k1_ecdsa_recover` in the root
   |                                    help: a similar name exists in the module: `secp256k1_ecdsa_verify`

For more information about this error, try `rustc --explain E0432`.

I assume the recovery module must be enabled or something of the sort.
I did add --enable-module-recovery to util/gen-fixtures/Makefile but no luck.

[junderw]

you need to enable the recovery feature in the Cargo.toml file entry for secp256k1-sys

[junderw]

secp256k1-sys = { version = "0.4.1", default-features = false, features = ["recovery"], git = "https://github.com/rust-bitcoin/rust-secp256k1", rev = "455ee57ba4051bb2cfea5f5f675378170fb42c7f" }

should give you a new recovery module to work with.

[motorina0]

should give you a new recovery module to work with.

No luck, exactly the same error. I can't see what I'm missing.
rust-secp256k1/Cargo.toml has

[features]
recovery = ["secp256k1-sys/recovery"]

rust-secp256k1/secp256k1-sys/Cargo.tom has

[features]
recovery = []

secp256k1-sys/build.rs has:

    #[cfg(feature = "recovery")]
    base_config.define("ENABLE_MODULE_RECOVERY", Some("1"));

According to dependency-features doc:

Features of dependencies can also be enabled in the [features] table. The syntax is "package-name/feature-name"

[junderw]

you need to import from the recovery submodule, not the root crate.

[junderw]

I am talking about tiny-secp256k1's Cargo.toml btw

[motorina0]

you need to import from the recovery submodule, not the root crate.

Thanks, that was the issue:
use secp256k1_sys::recovery::{ secp256k1_ecdsa_recover };

Noob mistake.

[motorina0]

PR merged. #69