rscrypto

Pure Rust cryptography: RSA, Ed25519, X25519, AEADs, hashes, KDFs, password hashing, CRCs, no_std, WASM, and hardware acceleration in one dependency.

rscrypto is a single primitive stack for projects that care about binary size, deployment control, and speed without a mandatory C, OpenSSL, or system lib story.

Use one leaf feature for one primitive, a group for a subset of primitives, or full for the whole shebang. The portable Rust backend is always present. SIMD and assembly are only accelerators.

Current benchmark scorecards: Linux CI is 1.61x fastest-external geomean with 3,545 / 5,832 wins and 5,210 / 5,832 wins-or-ties. Apple Silicon (MBP M1, macOS/aarch64 local full run) is 1.25x fastest-external geomean with 235 / 463 wins and 450 / 463 wins-or-ties.

Why rscrypto?

• RSA is now a first class citizen. Strict DER import/export, RSA-PSS, RSASSA-PKCS1-v1_5, OAEP, RSAES-PKCS1-v1_5, key generation, X.509/JWT/COSE/TLS profile mapping, blinded private operations, and reusable scratch APIs.
• One coherent primitive stack. Avoid composing half a dozen crates with different APIs, feature models, and security conventions.
• Small builds stay small. Enable sha2, blake3, aes-gcm, chacha20poly1305, ed25519, x25519, argon2, or any other leaf without pulling in the world.
• Portable Rust is the source of truth. SIMD and ASM paths are accelerators; the portable backend remains the reference implementation.
• Hardware dispatch is built in. x86/x86_64, Arm/AArch64, Apple Silicon, IBM Z, IBM POWER, RISC-V, and WASM all have portable fallbacks, with optimized kernels where they pay.
• no_std is a first-class target. Server, CLI, embedded, bare-metal, and WASM builds use the same crate and feature model.
• Audit knobs are explicit. portable-only forces runtime dispatch to the audited portable backend; getrandom, serde, and rayon are opt-in.
• Security hygiene is part of the API. Opaque verification errors, constant-time equality, zeroized secret types, strict arithmetic, official vectors, fuzzing, Miri, and cross-CPU CI are built into the project discipline.

rscrypto is a primitives crate. It is not a TLS stack, PKI toolkit, protocol implementation, or FIPS 140-3 validated module.

Install

Minimal no_std SHA-2 build:

[dependencies]
rscrypto = { version = "0.3.0", default-features = false, features = ["sha2"] }

Full primitive stack with OS randomness enabled:

[dependencies]
rscrypto = { version = "0.3.0", features = ["full", "getrandom"] }

Use default-features = false for constrained no_std builds. Enable getrandom only when you need APIs that generate salts, keys, or nonces from the operating system.

Quick Start

use rscrypto::{Digest, Sha256};

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

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

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

The common API shape is deliberately simple/boring: one-shot when convenient, streaming when it's needed.

Verify RSA Signatures

[dependencies]
rscrypto = { version = "0.3.0", default-features = false, features = ["rsa"] }

use rscrypto::{RsaPssProfile, RsaPublicKey};

fn verify_release_signature(public_key_der: &[u8], message: &[u8], signature: &[u8]) -> bool {
  let Ok(key) = RsaPublicKey::from_spki_der(public_key_der) else {
    return false;
  };

  key.verify_pss(RsaPssProfile::Sha256, message, signature).is_ok()
}

For repeated verification with the same key, allocate scratch once:

use rscrypto::{RsaPssProfile, RsaPublicKey, RsaSignatureProfile};

fn verify_batch(public_key_der: &[u8], signed_messages: &[(&[u8], &[u8])]) -> bool {
  let Ok(key) = RsaPublicKey::from_spki_der(public_key_der) else {
    return false;
  };
  let mut scratch = key.public_scratch();

  signed_messages.iter().all(|(message, signature)| {
    key
      .verify_signature_with_scratch(
        RsaSignatureProfile::pss(RsaPssProfile::Sha256),
        message,
        signature,
        &mut scratch,
      )
      .is_ok()
  })
}

Enable getrandom for OS-backed RSA key generation, signing salt/blinding, OAEP encryption randomness, and private-operation blinding:

[dependencies]
rscrypto = { version = "0.3.0", default-features = false, features = ["rsa", "getrandom"] }

Encrypt Data

[dependencies]
rscrypto = { version = "0.3.0", default-features = false, features = ["chacha20poly1305"] }

use rscrypto::{Aead, ChaCha20Poly1305, ChaCha20Poly1305Key, aead::Nonce96};

let key = ChaCha20Poly1305Key::from_bytes([0x11; 32]);
let nonce = Nonce96::from_bytes([0x22; Nonce96::LENGTH]);
let cipher = ChaCha20Poly1305::new(&key);

let aad = b"transfer:v1";
let mut message = *b"pay bob 10";

let tag = cipher
  .encrypt_in_place(&nonce, aad, &mut message)
  .expect("encryption succeeds");

cipher
  .decrypt_in_place(&nonce, aad, &mut message, &tag)
  .expect("authentication succeeds");

assert_eq!(&message, b"pay bob 10");

Hash Passwords

[dependencies]
rscrypto = { version = "0.3.0", default-features = false, features = ["argon2", "phc-strings", "getrandom"] }

use rscrypto::{Argon2Params, Argon2VerifyPolicy, Argon2id};

let password = b"correct horse battery staple";
let params = Argon2Params::new().build().expect("valid Argon2 params");
let encoded = Argon2id::hash_string(&params, password).expect("password hash created");

assert!(
  Argon2id::verify_string_with_policy(
    password,
    &encoded,
    &Argon2VerifyPolicy::default(),
  )
  .is_ok()
);

What You Get

Fast non-cryptographic hashes and CRCs are for indexing, checksumming, dedup, and integrity plumbing. Do not use them for passwords, signatures, MACs, key derivation, or authentication... it's obviously not safe.

Feature flags are layered deliberately:

• Leaf primitives: sha2, blake3, aes-gcm, ed25519, x25519, crc32, etc.
• Families/Groups: hashes, checksums, macs, kdfs, password-hashing, aead, signatures, key-exchange.
• Deployment controls: std, alloc, getrandom, parallel, serde, serde-secrets, portable-only.

Full feature inventory: docs/features.md. Public type inventory: docs/types.md.

Performance

Current public benchmark evidence comes from two passes:

• Linux CI: 2026-05-27, commit 26845c8, nine Linux runners. This run is filter-based and does not include Argon2, scrypt, or Ascon-AEAD rows.
• Apple Silicon: 2026-06-01, commit b06b946, local MBP M1 macOS/aarch64 full run, including Argon2, scrypt, and Ascon-AEAD rows.

Speedup is external_crate_time / rscrypto_time; values above 1.00x mean rscrypto is faster. Do not combine the Linux and Apple Silicon totals as one aggregate because they were collected on different commits and benchmark scopes.

The honest weak spots right now: Linux CI still shows PBKDF2-SHA256 at iters=1 at 0.81x, X25519 Diffie-Hellman at 0.92x, RSA-4096 verification at 0.94x, and small-message AEAD overhead on plenty of 1-byte and 32-byte rows. Apple Silicon still has BLAKE3 64 KiB losses, HMAC-SHA256 bulk pressure against aws-lc-rs, empty-message ChaCha20-Poly1305 overhead, and SHA3-256 streaming losses; SHA-3/SHAKE should be described per-platform because the Linux 2.15x SHA-3 result does not carry to the MBP M1 run. See benchmark_results/OVERVIEW.md for raw runs, methodology, platform scorecards, and loss tables.

Portability And Acceleration

rscrypto keeps the portable Rust path as the byte-for-byte authority. ISA-specific kernels are selected only when the target and runtime CPU support them.

Use portable-only when you need deterministic dispatch, audit-constrained builds, or a portable backend only.

Full platform matrix: docs/platforms.md. Architecture notes: docs/architecture.md.

Security

• Constant-time MAC, AEAD, and signature verification.
• Opaque verification errors that avoid leaking failure details.
• Secret-bearing types zeroize on drop and mask Debug.
• Strict arithmetic for counters, lengths, offsets, and indices.
• AEAD failed-open paths wipe output buffers.
• Portable and accelerated backends are differentially tested for byte-identical output.
• Official test vectors, fuzz corpus replay, Miri, cargo deny, and cargo audit run in CI.
• RSA private-operation release claims require the manual Miri and first-order leakage gates in docs/security/rsa-side-channel-audit.md.

Read docs/security.md before shipping cryptographic code. For compliance posture, see docs/compliance.md.

Vulnerabilities should be reported through GitHub Private Vulnerability Reporting or the process in SECURITY.md.

Docs

• API reference: docs.rs/rscrypto
• Examples: examples/
• Feature flags: docs/features.md
• Public type inventory: docs/types.md
• Platform matrix: docs/platforms.md
• Security guidance: docs/security.md
• Migration guides: docs/migration/
• Benchmark methodology: docs/benchmarking.md
• Benchmarks: benchmark_results/OVERVIEW.md
• Release history: CHANGELOG.md

MSRV

Rust 1.91.0.

The pinned nightly in rust-toolchain.toml is used for Miri, fuzzing, and exotic-architecture checks.

License

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