* Impl `signature::Digest*` traits for Ed25519ph
Adds the following trait impls:
- impl DigestSigner for SigningKey
- impl DigestVerifier for VerifyingKey
These traits can be used to create and verify Ed25519 signatures,
thunking to `SigningKey::sign_prehashed` and
`VerifyingKey::verify_prehashed` respectively.
* Add rustdoc comments for trait impls
* Add on-by-default `fast` crate feature
Disabling the feature reduces overall code size at the cost of
performance, which is useful for e.g. embedded users.
This feature transitively enables the `basepoint-tables` feature in
`curve25519-dalek` where the basepoint tables are actually defined.
* Consolidated a lot of verification code
* Bump `curve25519-dalek`; use `precomputed-tables` feature
The feature name changed in dalek-cryptography/curve25519-dalek#499
Co-authored-by: Michael Rosenberg <michael@mrosenberg.pub>
Updates to the latest upstream changes in `curve25519-dalek`, including
using the new `EdwardsPoint::mul_base` API.
To keep the build deterministic, this also checks in Cargo.lock, which
pins `curve25519-dalek` to a particular git commit SHA which can be
updated using `cargo update -p curve25519-dalek`.
We can potentially remove `Cargo.lock` again after a crate release.
