Crate ed25519_compact

source ·
Expand description

A compact Ed25519 and X25519 implementation for Rust.

  • Formally-verified Curve25519 field arithmetic
  • no_std-friendly
  • WebAssembly-friendly
  • Compute@Edge-friendly
  • Lightweight
  • Zero dependencies if randomness is provided by the application
  • Only one portable dependency (getrandom) if not
  • Supports incremental signatures (streaming API)
  • Safe and simple Rust interface.

Example usage:

use ed25519_compact::*;

// A message to sign and verify.
let message = b"test";

// Generates a new key pair using a random seed.
// A given seed will always produce the same key pair.
let key_pair = KeyPair::from_seed(Seed::generate());

// Computes a signature for this message using the secret part of the key pair.
let signature =, Some(Noise::generate()));

// Verifies the signature using the public part of the key pair.
    .verify(message, &signature)
    .expect("Signature didn't verify");

// Verification of a different message using the same signature and public key fails.
    .verify(b"A different message", &signature)
    .expect_err("Signature shouldn't verify");

// All these structures can be viewed as raw bytes simply by dereferencing them:
let signature_as_bytes: &[u8] = signature.as_ref();
println!("Signature as bytes: {:?}", signature_as_bytes);

Incremental API example usage

Messages can also be supplied as multiple parts (streaming API) in order to handle large messages without using much memory:

use ed25519_compact::*;

/// Creates a new key pair.
let kp = KeyPair::generate();

/// Create a state for an incremental signer.
let mut st =;

/// Feed the message as any number of chunks, and sign the concatenation.
let signature = st.sign();

/// Create a state for an incremental verifier.
let mut st =;

/// Feed the message as any number of chunks, and verify the concatenation.

Cargo features:

  • self-verify: after having computed a new signature, verify that is it valid. This is slower, but improves resilience against fault attacks. It is enabled by default on WebAssembly targets.
  • std: disables no_std compatibility in order to make errors implement the standard Error trait.
  • random (enabled by default): adds Default and generate implementations to the Seed and Noise objects, in order to securely create random keys and noise.
  • traits: add support for the traits from the ed25519 and signature crates.
  • pem: add support for importing/exporting keys as OpenSSL-compatible PEM files.
  • blind-keys: add support for key blinding.
  • opt_size: Enable size optimizations (based on benchmarks, 8-15% size reduction at the cost of 6.5-7% performance).
  • x25519: Enable support for the X25519 key exchange system.
  • disable-signatures: Disable support for signatures, and only compile support for X25519.



A key pair.
Noise, for non-deterministic signatures.
A public key.
A secret key.
A seed, which a key pair can be derived from.
An Ed25519 signature.
The state of a streaming signature operation.
The state of a streaming verification operation.