rscrypto puts cryptographic primitives, cryptographic and fast hashes, password hashing, and checksums behind one feature model. Target-gated SIMD and assembly accelerate portable Rust backends without a production C/FFI, OpenSSL, or system-library dependency.

rscrypto is a primitives crate, not a TLS stack, PKI toolkit, key store, or protocol implementation.

Measured performance

The 2026-08-18 snapshot compares commit 7eb44e9 with the fastest matched external implementation for each platform, primitive, operation, and input shape across eight Linux CI runners. The external baseline is selected case by case, not averaged across competitors. Ratios are external / rscrypto; higher is better.

Across 6,144 exact-case comparisons, rscrypto was more than 5% faster in 3,780, within 5% in 1,695, and slower in 669. The geometric-mean speedup was 1.62x overall, including 6.18x for checksums, 1.65x for RSA, 1.61x for AEAD, and 1.55x for ML-KEM.

The Apple Silicon result in the chart is a separate 2026-07-04 local snapshot; it is not included in the Linux aggregate.

This is an overall suite lead, not a claim that every operation wins. The same snapshot publishes the s390x ECDSA regression and the slower rapidhash-stream/one-write path alongside every raw row. Read the benchmark overview for the complete scorecard and benchmarking guide before applying a result to a deployment workload.

Assurance

Security claims fail closed: missing or stale evidence removes the claim rather than weakening the gate.

• Correctness evidence combines NIST, RFC, upstream, and Wycheproof vectors with separate implementations, properties, negative tests, and Miri.
• Fuzz targets exercise production implementations across primitive, parser, state-machine, and trait boundaries. Minimized seeds replay as tests, with a separate sanitizer lane.
• Portable-versus-accelerated differential tests cover lengths, alignments, tails, state transitions, dispatch, and fallback behavior on native targets.
• The constant-time harness inventories exact operations in ct.toml and combines optimized linked-binary inspection, BINSEC proofs for declared fixed-shape kernels, and DudeCT timing tests for declared end-to-end cases.
• Fixed-size secret owners mask Debug, omit ordinary equality, and overwrite owned bytes on drop. Verification failures are opaque; failed AEAD opens clear caller output buffers.

A constant-time claim exists only when the matching signed release includes an attested evidence bundle whose required target, feature, compiler, profile, and operation gates pass. Source that looks branchless is not treated as proof. Release artifacts are signed-tag gated, published through crates.io Trusted Publishing, and covered by GitHub build-provenance attestations.

Inspect the test evidence, constant-time model, secret lifecycle, threat model, and release contract.

The remaining independent-review gap is a third-party security audit. The project cannot currently fund one. Automated evidence does not replace that review, so rscrypto does not claim to be audited, FIPS 140-3 validated, formally verified, or constant time as a whole crate.

Report suspected vulnerabilities through GitHub Private Vulnerability Reporting under the SECURITY.md process, not a public issue.

Install only what you use

Minimal no_std SHA-2 build:

[dependencies]
rscrypto = { version = "0.9", default-features = false, features = ["sha2"] }

Full primitive stack with OS randomness enabled:

[dependencies]
rscrypto = { version = "0.9", features = ["full", "getrandom"] }

The default feature is std; default-features = false removes it. Enable getrandom only for APIs that obtain salts, keys, nonces, or RSA key-generation entropy from the operating system. The feature guide owns exact dependencies and deployment controls.

Quick start

use rscrypto::Sha256;

let one_shot = Sha256::digest(b"hello world");

let mut hasher = Sha256::new();
hasher.update(b"hello ");
hasher.update(b"world");

assert_eq!(hasher.finalize(), one_shot);

Hash APIs support one-shot and streaming use. Runnable workflows for AEAD, signatures, RSA, X25519, ML-KEM, password hashing, and backend introspection are in examples/README.md.

Primitive and feature map

Use docs.rs for exact types and methods. Use the migration guide when replacing another library.

Platforms and dispatch

The portable Rust implementation is the byte-for-byte authority. Compile-time target support and, with std, detected runtime CPU capabilities select eligible SIMD or assembly kernels. Unsupported acceleration falls back to portable Rust.

The platform guide owns the target matrix, dispatch model, no_std coverage, and the limits of portable-only.

Project

Read CONTRIBUTING.md before changing code. Published changes live in CHANGELOG.md.

License

Dual-licensed under Apache-2.0 or MIT, at your option.