Cargo Features

web3-signature has no features set by default.

[dependencies]
web3-signature = { version = "0.4.0", features = ["single-party"] }
single-party = k256

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

k256 single-party?