mirror of
https://github.com/saymrwulf/risc0-curve25519-dalek-source.git
synced 2026-09-04 20:03:40 +00:00
Implement simplified backend selection (#428)
As proposed in #414, this commit changes the backend selection approach, introspecting `target_pointer_width` to select `u32_backend` vs `u64_backend` (or `fiat_u32_backend`/`fiat_u64_backend` if the `fiat_backend` feature is enabled). This helps eliminate the use of non-additive features, and also the rather confusing errors that happen if multiple backends are selected (i.e. thousands of lines of rustc errors). The selection logic checks if `target_pointer_width = "64"` and uses the 64-bit backend, or falls back to the 32-bit backend otherwise. This means the crate will always have a valid backend regardless of the pointer width, although there may be odd edge cases for exotic platforms which would optimally use the 64-bit backend but have a non-"64" target pointer width for whatever reason. We can handle those cases as they come up.
This commit is contained in:
Tony Arcieri
GitHub
parent
977eb0d3b7
commit
081f632d91
8 changed files with 159 additions and 147 deletions
35
.github/workflows/rust.yml
vendored
35
.github/workflows/rust.yml
vendored
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@ -10,21 +10,24 @@ env:
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CARGO_TERM_COLOR: always
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jobs:
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test-u32:
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name: Test u32 backend
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test:
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runs-on: ubuntu-latest
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steps:
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- uses: actions/checkout@v3
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- uses: dtolnay/rust-toolchain@stable
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- run: cargo test --no-default-features --features "std u32_backend"
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strategy:
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matrix:
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include:
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# 32-bit target
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- target: i686-unknown-linux-gnu
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deps: sudo apt update && sudo apt install gcc-multilib
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test-u64:
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name: Test u64 backend
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runs-on: ubuntu-latest
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# 64-bit target
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- target: x86_64-unknown-linux-gnu
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steps:
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- uses: actions/checkout@v3
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- uses: dtolnay/rust-toolchain@stable
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- run: cargo test --no-default-features --features "std u64_backend"
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- uses: actions/checkout@v3
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- uses: dtolnay/rust-toolchain@stable
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- run: rustup target add ${{ matrix.target }}
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- run: ${{ matrix.deps }}
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- run: cargo test --target ${{ matrix.target }}
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- run: cargo test --target ${{ matrix.target }} --features fiat_backend
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build-simd:
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name: Build simd backend (nightly)
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@ -54,7 +57,9 @@ jobs:
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steps:
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- uses: actions/checkout@v3
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- uses: dtolnay/rust-toolchain@stable
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- run: cargo test --lib --no-default-features --features "alloc u32_backend"
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- run: rustup target add i686-unknown-linux-gnu
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- run: sudo apt update && sudo apt install gcc-multilib
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- run: cargo test --lib --no-default-features --features alloc --target i686-unknown-linux-gnu
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nightly:
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name: Test nightly compiler
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@ -72,11 +77,11 @@ jobs:
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# First run `cargo +nightly -Z minimal-verisons check` in order to get a
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# Cargo.lock with the oldest possible deps
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- uses: dtolnay/rust-toolchain@nightly
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- run: cargo -Z minimal-versions check --no-default-features --features "fiat_u64_backend serde"
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- run: cargo -Z minimal-versions check --no-default-features --features fiat_backend,serde
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# Now check that `cargo build` works with respect to the oldest possible
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# deps and the stated MSRV
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- uses: dtolnay/rust-toolchain@1.56.1
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- run: cargo build --no-default-features --features "fiat_u64_backend serde"
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- run: cargo build --no-default-features --features fiat_backend,serde
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bench:
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name: Check that benchmarks compile
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18
Cargo.toml
18
Cargo.toml
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@ -43,6 +43,7 @@ name = "dalek_benchmarks"
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harness = false
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[dependencies]
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cfg-if = "1"
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rand_core = { version = "0.6", default-features = false }
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digest = { version = "0.10", default-features = false }
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subtle = { version = "^2.2.1", default-features = false }
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@ -55,20 +56,11 @@ fiat-crypto = { version = "0.1.6", optional = true}
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[features]
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nightly = ["subtle/nightly"]
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default = ["std", "u64_backend"]
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default = ["std"]
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std = ["alloc", "subtle/std", "rand_core/std"]
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alloc = ["zeroize/alloc"]
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# The u32 backend uses u32s with u64 products.
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u32_backend = []
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# The u64 backend uses u64s with u128 products.
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u64_backend = []
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# fiat-u64 backend (with formally-verified field arith) uses u64s with u128 products.
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fiat_u64_backend = ["fiat-crypto"]
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# fiat-u32 backend (with formally-verified field arith) uses u32s with u64 products.
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fiat_u32_backend = ["fiat-crypto"]
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# fiat-crypto backend with formally-verified field arithmetic
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fiat_backend = ["fiat-crypto"]
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# The SIMD backend uses parallel formulas, using either AVX2 or AVX512-IFMA.
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simd_backend = ["nightly", "u64_backend", "packed_simd"]
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# DEPRECATED: this is now an alias for `simd_backend` and may be removed
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# in some future release.
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avx2_backend = ["simd_backend"]
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simd_backend = ["nightly", "packed_simd"]
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49
README.md
49
README.md
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@ -82,9 +82,13 @@ version, and in terms of non-breaking changes it includes:
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### 4.x (current alpha)
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The `4.x` series has an API largely unchanged from `3.x`, with a breaking change
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to update the `rand` dependency crates. It also requires including a new trait,
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`use curve25519_dalek::traits::BasepointTable`, whenever using `EdwardsBasepointTable`
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or `RistrettoBasepointTable`.
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to update the `rand` dependency crates.
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It also requires including a new trait,
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`use curve25519_dalek::traits::BasepointTable`, whenever using
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`EdwardsBasepointTable` or `RistrettoBasepointTable`.
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Backend selection has also been updated to be more automatic. See below.
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# Backends and Features
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@ -98,24 +102,26 @@ Curve arithmetic is implemented using one of the following backends:
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* a `u64` backend using serial formulas and `u128` products;
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* an `avx2` backend using [parallel formulas][parallel_doc] and `avx2` instructions (sets speed records);
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* an `ifma` backend using [parallel formulas][parallel_doc] and `ifma` instructions (sets speed records);
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By default the `u64` backend is selected. To select a specific backend, use:
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```sh
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cargo build --no-default-features --features "std u32_backend"
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cargo build --no-default-features --features "std u64_backend"
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# Requires nightly, RUSTFLAGS="-C target_feature=+avx2" to use avx2
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cargo build --no-default-features --features "std simd_backend"
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# Requires nightly, RUSTFLAGS="-C target_feature=+avx512ifma" to use ifma
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cargo build --no-default-features --features "std simd_backend"
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```
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Crates using `curve25519-dalek` can either select a backend on behalf of their
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users, or expose feature flags that control the `curve25519-dalek` backend.
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* a `fiat` backend using formally verified field arithmetic from [fiat-crypto];
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The `std` feature is enabled by default, but it can be disabled for no-`std`
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builds using `--no-default-features`. Note that this requires explicitly
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selecting an arithmetic backend using one of the `_backend` features.
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If no backend is selected, compilation will fail.
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## Backend selection
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Backend selection is done automatically. E.g., if you're compiling on a
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64-bit machine, then the `u64` backend is automatically chosen. And
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if the `fiat_backend` feature is set, then the fiat `u64` backend is
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chosen.
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If you need a `u32` backend on a `u64` machine, then simple
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cross-compiling will work on an x86-64 Linux machine:
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* `sudo apt install gcc-multilib` (or whatever package manager you use)
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* `rustup target add i686-unknown-linux-gnu`
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* `cargo build --target i686-unknown-linux-gnu`
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# Minimum Supported Rust Version
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@ -166,11 +172,10 @@ compiled with appropriate `target_feature`s, so this cannot occur.
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Benchmarks are run using [`criterion.rs`][criterion]:
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```sh
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cargo bench --no-default-features --features "std u32_backend"
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cargo bench --no-default-features --features "std u64_backend"
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cargo bench --no-default-features
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# Uses avx2 or ifma only if compiled for an appropriate target.
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export RUSTFLAGS="-C target_cpu=native"
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cargo bench --no-default-features --features "std simd_backend"
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cargo +nightly bench --no-default-features --features simd_backend
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```
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Performance is a secondary goal behind correctness, safety, and
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@ -227,10 +232,9 @@ optimised batch inversion was contributed by Sean Bowe and Daira Hopwood.
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The `no_std` and `zeroize` support was contributed by Tony Arcieri.
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The formally verified backends, `fiat_u32_backend` and `fiat_u64_backend`, which
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integrate with the Rust generated by the
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[Fiat Crypto project](https://github.com/mit-plv/fiat-crypto) were contributed
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by François Garillot.
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The formally verified `fiat_backend` integrates Rust code generated by the
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[Fiat Crypto project](https://github.com/mit-plv/fiat-crypto) and was
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contributed by François Garillot.
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Thanks also to Ashley Hauck, Lucas Salibian, Manish Goregaokar, Jack Grigg,
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Pratyush Mishra, Michael Rosenberg, and countless others for their
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@ -244,3 +248,4 @@ contributions.
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[criterion]: https://github.com/japaric/criterion.rs
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[parallel_doc]: https://doc-internal.dalek.rs/curve25519_dalek/backend/vector/avx2/index.html
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[subtle_doc]: https://doc.dalek.rs/subtle/
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[fiat-crypto]: https://github.com/mit-plv/fiat-crypto
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@ -34,18 +34,6 @@
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//! The [`vector`] backend is selected by the `simd_backend` cargo
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//! feature; it uses the [`serial`] backend for non-vectorized operations.
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#[cfg(not(any(
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feature = "u32_backend",
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feature = "u64_backend",
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feature = "fiat_u32_backend",
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feature = "fiat_u64_backend",
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feature = "simd_backend",
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)))]
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compile_error!(
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"no curve25519-dalek backend cargo feature enabled! \
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please enable one of: u32_backend, u64_backend, fiat_u32_backend, fiat_u64_backend, simd_backend"
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);
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pub mod serial;
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#[cfg(any(
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@ -19,32 +19,24 @@
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//!
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//! When the vector backend is enabled, the field and scalar
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//! implementations are still used for non-vectorized operations.
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//!
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//! Note: at this time the `u32` and `u64` backends cannot be built
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//! together.
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#[cfg(not(any(
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feature = "u32_backend",
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feature = "u64_backend",
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feature = "fiat_u32_backend",
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feature = "fiat_u64_backend"
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)))]
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compile_error!(
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"no curve25519-dalek backend cargo feature enabled! \
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please enable one of: u32_backend, u64_backend, fiat_u32_backend, fiat_u64_backend"
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);
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use cfg_if::cfg_if;
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#[cfg(feature = "u32_backend")]
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pub mod u32;
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cfg_if! {
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if #[cfg(feature = "fiat_backend")] {
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#[cfg(not(target_pointer_width = "64"))]
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pub mod fiat_u32;
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#[cfg(feature = "u64_backend")]
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pub mod u64;
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#[cfg(target_pointer_width = "64")]
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pub mod fiat_u64;
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} else {
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#[cfg(not(target_pointer_width = "64"))]
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pub mod u32;
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#[cfg(feature = "fiat_u32_backend")]
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pub mod fiat_u32;
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#[cfg(feature = "fiat_u64_backend")]
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pub mod fiat_u64;
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#[cfg(target_pointer_width = "64")]
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pub mod u64;
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}
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}
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pub mod curve_models;
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@ -28,20 +28,27 @@
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#![allow(non_snake_case)]
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use cfg_if::cfg_if;
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use crate::edwards::CompressedEdwardsY;
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use crate::montgomery::MontgomeryPoint;
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use crate::ristretto::CompressedRistretto;
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use crate::ristretto::RistrettoPoint;
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use crate::scalar::Scalar;
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#[cfg(feature = "fiat_u32_backend")]
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pub use crate::backend::serial::fiat_u32::constants::*;
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#[cfg(feature = "fiat_u64_backend")]
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pub use crate::backend::serial::fiat_u64::constants::*;
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#[cfg(feature = "u32_backend")]
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pub use crate::backend::serial::u32::constants::*;
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#[cfg(feature = "u64_backend")]
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pub use crate::backend::serial::u64::constants::*;
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cfg_if! {
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if #[cfg(feature = "fiat_backend")] {
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#[cfg(not(target_pointer_width = "64"))]
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pub use crate::backend::serial::fiat_u32::constants::*;
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#[cfg(target_pointer_width = "64")]
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pub use crate::backend::serial::fiat_u64::constants::*;
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} else {
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#[cfg(not(target_pointer_width = "64"))]
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pub use crate::backend::serial::u32::constants::*;
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#[cfg(target_pointer_width = "64")]
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pub use crate::backend::serial::u64::constants::*;
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}
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}
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/// The Ed25519 basepoint, in `CompressedEdwardsY` format.
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///
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@ -142,7 +149,7 @@ mod test {
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/// Test that d = -121665/121666
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#[test]
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#[cfg(feature = "u32_backend")]
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#[cfg(all(not(target_pointer_width = "64"), not(feature = "fiat_backend")))]
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fn test_d_vs_ratio() {
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use crate::backend::serial::u32::field::FieldElement2625;
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let a = -&FieldElement2625([121665, 0, 0, 0, 0, 0, 0, 0, 0, 0]);
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@ -155,7 +162,7 @@ mod test {
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/// Test that d = -121665/121666
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#[test]
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#[cfg(feature = "u64_backend")]
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#[cfg(all(target_pointer_width = "64", not(feature = "fiat_backend")))]
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fn test_d_vs_ratio() {
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use crate::backend::serial::u64::field::FieldElement51;
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let a = -&FieldElement51([121665, 0, 0, 0, 0]);
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78
src/field.rs
78
src/field.rs
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@ -25,6 +25,8 @@
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use core::cmp::{Eq, PartialEq};
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use cfg_if::cfg_if;
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use subtle::Choice;
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use subtle::ConditionallyNegatable;
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use subtle::ConditionallySelectable;
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@ -33,40 +35,52 @@ use subtle::ConstantTimeEq;
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use crate::backend;
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use crate::constants;
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#[cfg(feature = "fiat_u32_backend")]
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pub use backend::serial::fiat_u32::field::*;
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#[cfg(feature = "fiat_u64_backend")]
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pub use backend::serial::fiat_u64::field::*;
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/// A `FieldElement` represents an element of the field
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/// \\( \mathbb Z / (2\^{255} - 19)\\).
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///
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/// The `FieldElement` type is an alias for one of the platform-specific
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/// implementations.
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/// Using formally-verified field arithmetic from fiat-crypto
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#[cfg(feature = "fiat_u32_backend")]
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pub type FieldElement = backend::serial::fiat_u32::field::FieldElement2625;
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#[cfg(feature = "fiat_u64_backend")]
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pub type FieldElement = backend::serial::fiat_u64::field::FieldElement51;
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cfg_if! {
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if #[cfg(feature = "fiat_backend")] {
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#[cfg(not(target_pointer_width = "64"))]
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pub use backend::serial::fiat_u32::field::*;
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#[cfg(target_pointer_width = "64")]
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pub use backend::serial::fiat_u64::field::*;
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#[cfg(feature = "u64_backend")]
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pub use crate::backend::serial::u64::field::*;
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/// A `FieldElement` represents an element of the field
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/// \\( \mathbb Z / (2\^{255} - 19)\\).
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///
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/// The `FieldElement` type is an alias for one of the platform-specific
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/// implementations.
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#[cfg(feature = "u64_backend")]
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pub type FieldElement = backend::serial::u64::field::FieldElement51;
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/// A `FieldElement` represents an element of the field
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/// \\( \mathbb Z / (2\^{255} - 19)\\).
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///
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/// The `FieldElement` type is an alias for one of the platform-specific
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/// implementations.
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///
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/// Using formally-verified field arithmetic from fiat-crypto.
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#[cfg(not(target_pointer_width = "64"))]
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pub type FieldElement = backend::serial::fiat_u32::field::FieldElement2625;
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#[cfg(feature = "u32_backend")]
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pub use backend::serial::u32::field::*;
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/// A `FieldElement` represents an element of the field
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/// \\( \mathbb Z / (2\^{255} - 19)\\).
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///
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/// The `FieldElement` type is an alias for one of the platform-specific
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/// implementations.
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#[cfg(feature = "u32_backend")]
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pub type FieldElement = backend::serial::u32::field::FieldElement2625;
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/// A `FieldElement` represents an element of the field
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/// \\( \mathbb Z / (2\^{255} - 19)\\).
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///
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/// The `FieldElement` type is an alias for one of the platform-specific
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/// implementations.
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///
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/// Using formally-verified field arithmetic from fiat-crypto.
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#[cfg(target_pointer_width = "64")]
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pub type FieldElement = backend::serial::fiat_u64::field::FieldElement51;
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} else if #[cfg(target_pointer_width = "64")] {
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pub use crate::backend::serial::u64::field::*;
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/// A `FieldElement` represents an element of the field
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/// \\( \mathbb Z / (2\^{255} - 19)\\).
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///
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/// The `FieldElement` type is an alias for one of the platform-specific
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/// implementations.
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pub type FieldElement = backend::serial::u64::field::FieldElement51;
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} else {
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pub use backend::serial::u32::field::*;
|
||||
|
||||
/// A `FieldElement` represents an element of the field
|
||||
/// \\( \mathbb Z / (2\^{255} - 19)\\).
|
||||
///
|
||||
/// The `FieldElement` type is an alias for one of the platform-specific
|
||||
/// implementations.
|
||||
pub type FieldElement = backend::serial::u32::field::FieldElement2625;
|
||||
}
|
||||
}
|
||||
|
||||
impl Eq for FieldElement {}
|
||||
|
||||
|
|
|
|||
|
|
@ -150,6 +150,8 @@ use core::ops::{Sub, SubAssign};
|
|||
#[allow(unused_imports)]
|
||||
use crate::prelude::*;
|
||||
|
||||
use cfg_if::cfg_if;
|
||||
|
||||
use rand_core::{CryptoRng, RngCore};
|
||||
|
||||
use digest::generic_array::typenum::U64;
|
||||
|
|
@ -164,28 +166,35 @@ use zeroize::Zeroize;
|
|||
use crate::backend;
|
||||
use crate::constants;
|
||||
|
||||
/// An `UnpackedScalar` represents an element of the field GF(l), optimized for speed.
|
||||
///
|
||||
/// This is a type alias for one of the scalar types in the `backend`
|
||||
/// module.
|
||||
#[cfg(feature = "fiat_u32_backend")]
|
||||
type UnpackedScalar = backend::serial::fiat_u32::scalar::Scalar29;
|
||||
#[cfg(feature = "fiat_u64_backend")]
|
||||
type UnpackedScalar = backend::serial::fiat_u64::scalar::Scalar52;
|
||||
cfg_if! {
|
||||
if #[cfg(feature = "fiat_backend")] {
|
||||
/// An `UnpackedScalar` represents an element of the field GF(l), optimized for speed.
|
||||
///
|
||||
/// This is a type alias for one of the scalar types in the `backend`
|
||||
/// module.
|
||||
#[cfg(not(target_pointer_width = "64"))]
|
||||
type UnpackedScalar = backend::serial::fiat_u32::scalar::Scalar29;
|
||||
|
||||
/// An `UnpackedScalar` represents an element of the field GF(l), optimized for speed.
|
||||
///
|
||||
/// This is a type alias for one of the scalar types in the `backend`
|
||||
/// module.
|
||||
#[cfg(feature = "u64_backend")]
|
||||
type UnpackedScalar = backend::serial::u64::scalar::Scalar52;
|
||||
|
||||
/// An `UnpackedScalar` represents an element of the field GF(l), optimized for speed.
|
||||
///
|
||||
/// This is a type alias for one of the scalar types in the `backend`
|
||||
/// module.
|
||||
#[cfg(feature = "u32_backend")]
|
||||
type UnpackedScalar = backend::serial::u32::scalar::Scalar29;
|
||||
/// An `UnpackedScalar` represents an element of the field GF(l), optimized for speed.
|
||||
///
|
||||
/// This is a type alias for one of the scalar types in the `backend`
|
||||
/// module.
|
||||
#[cfg(target_pointer_width = "64")]
|
||||
type UnpackedScalar = backend::serial::fiat_u64::scalar::Scalar52;
|
||||
} else if #[cfg(target_pointer_width = "64")] {
|
||||
/// An `UnpackedScalar` represents an element of the field GF(l), optimized for speed.
|
||||
///
|
||||
/// This is a type alias for one of the scalar types in the `backend`
|
||||
/// module.
|
||||
type UnpackedScalar = backend::serial::u64::scalar::Scalar52;
|
||||
} else {
|
||||
/// An `UnpackedScalar` represents an element of the field GF(l), optimized for speed.
|
||||
///
|
||||
/// This is a type alias for one of the scalar types in the `backend`
|
||||
/// module.
|
||||
type UnpackedScalar = backend::serial::u32::scalar::Scalar29;
|
||||
}
|
||||
}
|
||||
|
||||
/// The `Scalar` struct holds an integer \\(s < 2\^{255} \\) which
|
||||
/// represents an element of \\(\mathbb Z / \ell\\).
|
||||
|
|
|
|||
Loading…
Reference in a new issue