chore: Release 2.0.0-rc.3 (#128)

* chore: Release 2.0.0-rc.3

* cargo update -p curve25519-dalek

* Added note about backends

* Fixed docs broken link

---------

Co-authored-by: Michael Rosenberg <michael@mrosenberg.pub>

CHANGELOG.md

@@ -4,10 +4,14 @@ Entries are listed in reverse chronological order.
 
 # 2.x Series
 
+* Note: All `x255919-dalek` 2.x releases are in sync with the underlying `curve25519-dalek` 4.x releases. 
 
 ## 2.0.0-rc.3
 
-* Change: `StaticSecret` serialization and `to_bytes()` no longer returns clamped integers. Clamping is still always done during scalar-point multiplication.
+* `StaticSecret` serialization and `to_bytes()` no longer returns clamped integers. Clamping is still always done during scalar-point multiplication.
+* Update underlying `curve25519_dalek` library to `4.0.0-rc.3`. Notable changes:
+    * [curve25519-dalek backend] now by default auto selects `simd` backend over `serial` where supported.
+
 
 ## 2.0.0-rc.2
 
@@ -16,7 +20,9 @@ Entries are listed in reverse chronological order.
 * Add `.as_bytes()` and `AsRef<[u8]>` for `Shared/StaticSecret`
 * Add `getrandom` feature to provide `random_from_rng` constructors
 * Make `StaticSecrets` optional via feature `static_secrets`
-* Update underlying `curve25519_dalek` library to `4.0.0-rc.2`
+* Update underlying `curve25519_dalek` library to `4.0.0-rc.2`. Notable changes:
+    * [curve25519-dalek backend] additive features have been removed in favor of cfg based selection.
+    * [curve25519-dalek backend] now by default auto selects the appropriate word size over the previous default `32`.
 
 ## 2.0.0-pre.1
 
@@ -88,3 +94,5 @@ Entries are listed in reverse chronological order.
 
 * Adds support for static and ephemeral keys.
 
+[curve25519-dalek backend]: https://github.com/dalek-cryptography/curve25519-dalek/#backends 
+

Cargo.toml

@@ -6,7 +6,7 @@ edition = "2021"
 # - update html_root_url
 # - update CHANGELOG
 # - if any changes were made to README.md, mirror them in src/lib.rs docs
-version = "2.0.0-rc.2"
+version = "2.0.0-rc.3"
 authors = [
     "Isis Lovecruft <isis@patternsinthevoid.net>",
     "DebugSteven <debugsteven@gmail.com>",
@@ -38,7 +38,7 @@ rustdoc-args = [
 features = ["getrandom", "reusable_secrets", "serde", "static_secrets"]
 
 [dependencies]
-curve25519-dalek = { version = "4.0.0-rc.2", default-features = false }
+curve25519-dalek = { version = "=4.0.0-rc.3", default-features = false }
 rand_core = { version = "0.6", default-features = false }
 serde = { version = "1", default-features = false, optional = true, features = ["derive"] }
 zeroize = { version = "1", default-features = false, optional = true, features = ["zeroize_derive"] }
@@ -61,7 +61,3 @@ alloc = ["curve25519-dalek/alloc", "serde?/alloc", "zeroize?/alloc"]
 precomputed-tables = ["curve25519-dalek/precomputed-tables"]
 reusable_secrets = []
 static_secrets = []
-
-[patch.crates-io.curve25519-dalek]
-git = "https://github.com/dalek-cryptography/curve25519-dalek.git"
-rev = "f460ae149b0000695205cc78f560d74a2d3918eb"

README.md

@@ -100,7 +100,7 @@ To install, add the following to your project's `Cargo.toml`:
 
 ```toml
 [dependencies]
-x25519-dalek = "2.0.0-rc.2"
+x25519-dalek = "2.0.0-rc.3"
 ```
 
 # MSRV
@@ -111,6 +111,12 @@ Current MSRV is 1.60.
 
 Documentation is available [here](https://docs.rs/x25519-dalek).
 
+# Performance and backend selection
+
+Performance is a secondary goal behind correctness, safety, and clarity, but we aim to be competitive with other implementations. To this end, we allow users to choose their _backend_, i.e., the underlying implementation of elliptic curve and scalar arithmetic. Different backends have different use cases. For example, if you demand formally verified code, you want to use the `fiat` backend (as it was generated from [Fiat Crypto][fiat]).
+
+Further instructions and details regarding backends can be found in the [curve25519-dalek docs](https://github.com/dalek-cryptography/curve25519-dalek#backends).
+
 # Note
 
 This code matches the [RFC7748][rfc7748] test vectors.
@@ -129,4 +135,5 @@ copyright © Amy Wibowo ([@sailorhg](https://twitter.com/sailorhg))
   the NaCl family of encryption libraries (libsodium, TweetNaCl) which uses
   `x25519-dalek` for key agreement
 
+[fiat]: https://github.com/mit-plv/fiat-crypto
 [crypto_box]: https://github.com/RustCrypto/nacl-compat/tree/master/crypto_box