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Merge branch 'develop' into release/4.0

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Isis Lovecruft 2021-08-03 23:06:58 +00:00
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21
CHANGELOG.md
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@ -10,6 +10,11 @@ major series.
## 3.x series
### 3.1.1
* Fix documentation builds on nightly due to syntax changes to
`#![cfg_attr(feature = "nightly", doc = include_str!("../README.md"))]`.
### 3.1.0
* Add support for the Elligator2 encoding for Edwards points.
@ -25,9 +30,15 @@ major series.
consumers of `curve25519-dalek` should call these methods manually
when needed.
### 3.0.3
* Fix documentation builds on nightly due to syntax changes to
`#![cfg_attr(feature = "nightly", doc = include_str!("../README.md"))]`.
### 3.0.2
* Fixes to make using alloc+no_std possible for stable Rust.
* Multiple documenation typo fixes.
* Fixes to make using `alloc`+`no_std` possible for stable Rust.
### 3.0.1
@ -42,9 +53,15 @@ major series.
## 2.x series
### 2.1.3
* Fix documentation builds on nightly due to syntax changes to
`#![fg_attr(feature = "nightly", doc = include_str!("../README.md"))]`.
### 2.1.2
* Fixes to make using alloc+no_std possible for stable Rust.
* Multiple documenation typo fixes.
* Fix `alloc` feature working with stable rust.
### 2.1.1

1
Cargo.toml
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@ -4,6 +4,7 @@ name = "curve25519-dalek"
# - update CHANGELOG
# - update html_root_url
# - update README if required by semver
# - if README was updated, also update module documentation in src/lib.rs
version = "4.0.0-pre.0"
authors = ["Isis Lovecruft <isis@patternsinthevoid.net>",
"Henry de Valence <hdevalence@hdevalence.ca>"]

2
Makefile
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@ -1,4 +1,4 @@
FEATURES := nightly yolocrypto avx2_backend
FEATURES := nightly simd_backend
doc:
cargo rustdoc --features "$(FEATURES)" -- --html-in-header docs/assets/rustdoc-include-katex-header.html

8
README.md
View file

@ -220,7 +220,13 @@ optimised batch inversion was contributed by Sean Bowe and Daira Hopwood.
The `no_std` and `zeroize` support was contributed by Tony Arcieri.
Thanks also to Ashley Hauck, Lucas Salibian, and Manish Goregaokar for their
The formally verified backends, `fiat_u32_backend` and `fiat_u64_backend`, which
integrate with the Rust generated by the
[Fiat Crypto project](https://github.com/mit-plv/fiat-crypto) were contributed
by François Garillot.
Thanks also to Ashley Hauck, Lucas Salibian, Manish Goregaokar, Jack Grigg,
Pratyush Mishra, Michael Rosenberg, and countless others for their
contributions.
[ed25519-dalek]: https://github.com/dalek-cryptography/ed25519-dalek

2
src/backend/serial/scalar_mul/pippenger.rs
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@ -58,7 +58,7 @@ use prelude::*;
/// However, if `w` is too big and `n` is not too big, then `(2^w/2)*A` could dominate.
/// Therefore, the optimal choice of `w` grows slowly as `n` grows.
///
/// This algorithm is adapted from section 4 of https://eprint.iacr.org/2012/549.pdf.
/// This algorithm is adapted from section 4 of <https://eprint.iacr.org/2012/549.pdf>.
pub struct Pippenger;
#[cfg(any(feature = "alloc", feature = "std"))]

237
src/lib.rs
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@ -11,21 +11,240 @@
#![no_std]
#![cfg_attr(feature = "nightly", feature(test))]
#![cfg_attr(feature = "nightly", feature(external_doc))]
#![cfg_attr(feature = "nightly", feature(doc_cfg))]
#![cfg_attr(feature = "simd_backend", feature(stdsimd))]
// Refuse to compile if documentation is missing, but only on nightly.
//
// This means that missing docs will still fail CI, but means we can use
// README.md as the crate documentation.
#![cfg_attr(feature = "nightly", deny(missing_docs))]
#![cfg_attr(feature = "nightly", doc(include = "../README.md"))]
// Refuse to compile if documentation is missing.
#![deny(missing_docs)]
#![doc(html_logo_url = "https://doc.dalek.rs/assets/dalek-logo-clear.png")]
#![doc(html_root_url = "https://docs.rs/curve25519-dalek/4.0.0-pre.0")]
//! Note that docs will only build on nightly Rust until
//! [RFC 1990 stabilizes](https://github.com/rust-lang/rust/issues/44732).
//! # curve25519-dalek [![](https://img.shields.io/crates/v/curve25519-dalek.svg)](https://crates.io/crates/curve25519-dalek) [![](https://img.shields.io/badge/dynamic/json.svg?label=docs&uri=https%3A%2F%2Fcrates.io%2Fapi%2Fv1%2Fcrates%2Fcurve25519-dalek%2Fversions&query=%24.versions%5B0%5D.num&colorB=4F74A6)](https://doc.dalek.rs) [![](https://travis-ci.org/dalek-cryptography/curve25519-dalek.svg?branch=master)](https://travis-ci.org/dalek-cryptography/curve25519-dalek)
//!
//! <img
//! width="33%"
//! align="right"
//! src="https://doc.dalek.rs/assets/dalek-logo-clear.png"/>
//!
//! **A pure-Rust implementation of group operations on Ristretto and Curve25519.**
//!
//! `curve25519-dalek` is a library providing group operations on the Edwards and
//! Montgomery forms of Curve25519, and on the prime-order Ristretto group.
//!
//! `curve25519-dalek` is not intended to provide implementations of any particular
//! crypto protocol. Rather, implementations of those protocols (such as
//! [`x25519-dalek`][x25519-dalek] and [`ed25519-dalek`][ed25519-dalek]) should use
//! `curve25519-dalek` as a library.
//!
//! `curve25519-dalek` is intended to provide a clean and safe _mid-level_ API for use
//! implementing a wide range of ECC-based crypto protocols, such as key agreement,
//! signatures, anonymous credentials, rangeproofs, and zero-knowledge proof
//! systems.
//!
//! In particular, `curve25519-dalek` implements Ristretto, which constructs a
//! prime-order group from a non-prime-order Edwards curve. This provides the
//! speed and safety benefits of Edwards curve arithmetic, without the pitfalls of
//! cofactor-related abstraction mismatches.
//!
//! # Documentation
//!
//! The semver-stable, public-facing `curve25519-dalek` API is documented
//! [here][docs-external]. In addition, the unstable internal implementation
//! details are documented [here][docs-internal].
//!
//! The `curve25519-dalek` documentation requires a custom HTML header to include
//! KaTeX for math support. Unfortunately `cargo doc` does not currently support
//! this, but docs can be built using
//! ```sh
//! make doc
//! make doc-internal
//! ```
//!
//! # Use
//!
//! To import `curve25519-dalek`, add the following to the dependencies section of
//! your project's `Cargo.toml`:
//! ```toml
//! curve25519-dalek = "3"
//! ```
//!
//! The sole breaking change in the `3.x` series was an update to the `digest`
//! version, and in terms of non-breaking changes it includes:
//!
//! * support for using `alloc` instead of `std` on stable Rust,
//! * the Elligator2 encoding for Edwards points,
//! * a fix to use `packed_simd2`,
//! * various documentation fixes and improvements,
//! * support for configurably-sized, precomputed lookup tables for basepoint scalar
//! multiplication,
//! * two new formally-verified field arithmetic backends which use the Fiat Crypto
//! Rust code, which is generated from proofs of functional correctness checked by
//! the Coq theorem proving system, and
//! * support for explicitly calling the `zeroize` traits for all point types.
//!
//! The `2.x` series has API almost entirely unchanged from the `1.x` series,
//! except that:
//!
//! * an error in the data modeling for the (optional) `serde` feature was
//! corrected, so that when the `2.x`-series `serde` implementation is used
//! with `serde-bincode`, the derived serialization matches the usual X/Ed25519
//! formats;
//! * the `rand` version was updated.
//!
//! See `CHANGELOG.md` for more details.
//!
//! # Backends and Features
//!
//! The `nightly` feature enables features available only when using a Rust nightly
//! compiler. In particular, it is required for rendering documentation and for
//! the SIMD backends.
//!
//! Curve arithmetic is implemented using one of the following backends:
//!
//! * a `u32` backend using serial formulas and `u64` products;
//! * a `u64` backend using serial formulas and `u128` products;
//! * an `avx2` backend using [parallel formulas][parallel_doc] and `avx2` instructions (sets speed records);
//! * an `ifma` backend using [parallel formulas][parallel_doc] and `ifma` instructions (sets speed records);
//!
//! By default the `u64` backend is selected. To select a specific backend, use:
//! ```sh
//! cargo build --no-default-features --features "std u32_backend"
//! cargo build --no-default-features --features "std u64_backend"
//! # Requires nightly, RUSTFLAGS="-C target_feature=+avx2" to use avx2
//! cargo build --no-default-features --features "std simd_backend"
//! # Requires nightly, RUSTFLAGS="-C target_feature=+avx512ifma" to use ifma
//! cargo build --no-default-features --features "std simd_backend"
//! ```
//! Crates using `curve25519-dalek` can either select a backend on behalf of their
//! users, or expose feature flags that control the `curve25519-dalek` backend.
//!
//! The `std` feature is enabled by default, but it can be disabled for no-`std`
//! builds using `--no-default-features`. Note that this requires explicitly
//! selecting an arithmetic backend using one of the `_backend` features.
//! If no backend is selected, compilation will fail.
//!
//! # Safety
//!
//! The `curve25519-dalek` types are designed to make illegal states
//! unrepresentable. For example, any instance of an `EdwardsPoint` is
//! guaranteed to hold a point on the Edwards curve, and any instance of a
//! `RistrettoPoint` is guaranteed to hold a valid point in the Ristretto
//! group.
//!
//! All operations are implemented using constant-time logic (no
//! secret-dependent branches, no secret-dependent memory accesses),
//! unless specifically marked as being variable-time code.
//! We believe that our constant-time logic is lowered to constant-time
//! assembly, at least on `x86_64` targets.
//!
//! As an additional guard against possible future compiler optimizations,
//! the `subtle` crate places an optimization barrier before every
//! conditional move or assignment. More details can be found in [the
//! documentation for the `subtle` crate][subtle_doc].
//!
//! Some functionality (e.g., multiscalar multiplication or batch
//! inversion) requires heap allocation for temporary buffers. All
//! heap-allocated buffers of potentially secret data are explicitly
//! zeroed before release.
//!
//! However, we do not attempt to zero stack data, for two reasons.
//! First, it's not possible to do so correctly: we don't have control
//! over stack allocations, so there's no way to know how much data to
//! wipe. Second, because `curve25519-dalek` provides a mid-level API,
//! the correct place to start zeroing stack data is likely not at the
//! entrypoints of `curve25519-dalek` functions, but at the entrypoints of
//! functions in other crates.
//!
//! The implementation is memory-safe, and contains no significant
//! `unsafe` code. The SIMD backend uses `unsafe` internally to call SIMD
//! intrinsics. These are marked `unsafe` only because invoking them on an
//! inappropriate CPU would cause `SIGILL`, but the entire backend is only
//! compiled with appropriate `target_feature`s, so this cannot occur.
//!
//! # Performance
//!
//! Benchmarks are run using [`criterion.rs`][criterion]:
//!
//! ```sh
//! cargo bench --no-default-features --features "std u32_backend"
//! cargo bench --no-default-features --features "std u64_backend"
//! # Uses avx2 or ifma only if compiled for an appropriate target.
//! export RUSTFLAGS="-C target_cpu=native"
//! cargo bench --no-default-features --features "std simd_backend"
//! ```
//!
//! Performance is a secondary goal behind correctness, safety, and
//! clarity, but we aim to be competitive with other implementations.
//!
//! # FFI
//!
//! Unfortunately, we have no plans to add FFI to `curve25519-dalek` directly. The
//! reason is that we use Rust features to provide an API that maintains safety
//! invariants, which are not possible to maintain across an FFI boundary. For
//! instance, as described in the _Safety_ section above, invalid points are
//! impossible to construct, and this would not be the case if we exposed point
//! operations over FFI.
//!
//! However, `curve25519-dalek` is designed as a *mid-level* API, aimed at
//! implementing other, higher-level primitives. Instead of providing FFI at the
//! mid-level, our suggestion is to implement the higher-level primitive (a
//! signature, PAKE, ZKP, etc) in Rust, using `curve25519-dalek` as a dependency,
//! and have that crate provide a minimal, byte-buffer-oriented FFI specific to
//! that primitive.
//!
//! # Contributing
//!
//! Please see [CONTRIBUTING.md][contributing].
//!
//! Patches and pull requests should be make against the `develop`
//! branch, **not** `master`.
//!
//! # About
//!
//! **SPOILER ALERT:** *The Twelfth Doctor's first encounter with the Daleks is in
//! his second full episode, "Into the Dalek". A beleaguered ship of the "Combined
//! Galactic Resistance" has discovered a broken Dalek that has turned "good",
//! desiring to kill all other Daleks. The Doctor, Clara and a team of soldiers
//! are miniaturized and enter the Dalek, which the Doctor names Rusty. They
//! repair the damage, but accidentally restore it to its original nature, causing
//! it to go on the rampage and alert the Dalek fleet to the whereabouts of the
//! rebel ship. However, the Doctor manages to return Rusty to its previous state
//! by linking his mind with the Dalek's: Rusty shares the Doctor's view of the
//! universe's beauty, but also his deep hatred of the Daleks. Rusty destroys the
//! other Daleks and departs the ship, determined to track down and bring an end
//! to the Dalek race.*
//!
//! `curve25519-dalek` is authored by Isis Agora Lovecruft and Henry de Valence.
//!
//! Portions of this library were originally a port of [Adam Langley's
//! Golang ed25519 library](https://!github.com/agl/ed25519), which was in
//! turn a port of the reference `ref10` implementation. Most of this code,
//! including the 32-bit field arithmetic, has since been rewritten.
//!
//! The fast `u32` and `u64` scalar arithmetic was implemented by Andrew Moon, and
//! the addition chain for scalar inversion was provided by Brian Smith. The
//! optimised batch inversion was contributed by Sean Bowe and Daira Hopwood.
//!
//! The `no_std` and `zeroize` support was contributed by Tony Arcieri.
//!
//! The formally verified backends, `fiat_u32_backend` and `fiat_u64_backend`, which
//! integrate with the Rust generated by the
//! [Fiat Crypto project](https://github.com/mit-plv/fiat-crypto) were contributed
//! by François Garillot.
//!
//! Thanks also to Ashley Hauck, Lucas Salibian, Manish Goregaokar, Jack Grigg,
//! Pratyush Mishra, Michael Rosenberg, and countless others for their
//! contributions.
//!
//! [ed25519-dalek]: https://github.com/dalek-cryptography/ed25519-dalek
//! [x25519-dalek]: https://github.com/dalek-cryptography/x25519-dalek
//! [contributing]: https://github.com/dalek-cryptography/curve25519-dalek/blob/master/CONTRIBUTING.md
//! [docs-external]: https://doc.dalek.rs/curve25519_dalek/
//! [docs-internal]: https://doc-internal.dalek.rs/curve25519_dalek/
//! [criterion]: https://github.com/japaric/criterion.rs
//! [parallel_doc]: https://doc-internal.dalek.rs/curve25519_dalek/backend/vector/avx2/index.html
//! [subtle_doc]: https://doc.dalek.rs/subtle/
//------------------------------------------------------------------------
// External dependencies:

22
src/montgomery.rs
View file

@ -94,6 +94,13 @@ impl PartialEq for MontgomeryPoint {
impl Eq for MontgomeryPoint {}
impl Identity for MontgomeryPoint {
/// Return the group identity element, which has order 4.
fn identity() -> MontgomeryPoint {
MontgomeryPoint([0u8; 32])
}
}
impl Zeroize for MontgomeryPoint {
fn zeroize(&mut self) {
self.0.zeroize();
@ -159,7 +166,7 @@ impl MontgomeryPoint {
/// Perform the Elligator2 mapping to a Montgomery point.
///
/// See https://tools.ietf.org/html/draft-irtf-cfrg-hash-to-curve-10#section-6.7.1
/// See <https://tools.ietf.org/html/draft-irtf-cfrg-hash-to-curve-10#section-6.7.1>
//
// TODO Determine how much of the hash-to-group API should be exposed after the CFRG
// draft gets into a more polished/accepted state.
@ -351,6 +358,19 @@ mod test {
use rand_core::OsRng;
#[test]
fn identity_in_different_coordinates() {
let id_projective = ProjectivePoint::identity();
let id_montgomery = id_projective.to_affine();
assert!(id_montgomery == MontgomeryPoint::identity());
}
#[test]
fn identity_in_different_models() {
assert!(EdwardsPoint::identity().to_montgomery() == MontgomeryPoint::identity());
}
#[test]
#[cfg(feature = "serde")]
fn serde_bincode_basepoint_roundtrip() {