ed25519-dalek

Fast and efficient Rust implementation of ed25519 key generation, signing, and verification in Rust.

Documentation

Documentation is available here.

Benchmarks

You need to pass the --features="bench" flag to run the benchmarks. The reason for feature-gating the benchmarks is that Rust's test::Bencher is unstable, and thus only works on the nightly channel. (We'd like people to be able to compile and test on the stable and beta channels too!)

On an Intel i5 Sandy Bridge running at 2.6 GHz, with TurboBoost enabled (and also running in QubesOS with lots of other VMs executing), this code achieves the following performance benchmarks:

∃!isisⒶwintermute:(develop *$)~/code/rust/ed25519 ∴ cargo bench --features="bench"
    Finished release [optimized] target(s) in 0.0 secs
     Running target/release/deps/ed25519_dalek-281c2d7a2379edae

running 6 tests
test ed25519::test::golden ... ignored
test ed25519::test::sign_verify ... ignored
test ed25519::test::unmarshal_marshal ... ignored
test ed25519::bench::key_generation ... bench:      54,571 ns/iter (+/- 7,861)
test ed25519::bench::sign           ... bench:      70,009 ns/iter (+/- 22,812)
test ed25519::bench::verify         ... bench:     185,619 ns/iter (+/- 24,117)

test result: ok. 0 passed; 0 failed; 3 ignored; 3 measured

In comparison, the equivalent package in Golang performs as follows:

∃!isisⒶwintermute:(master *=)~/code/go/src/github.com/agl/ed25519 ∴ go test -bench .
PASS
BenchmarkKeyGeneration     20000             85880 ns/op
BenchmarkSigning           20000             89115 ns/op
BenchmarkVerification      10000            212585 ns/op
ok      github.com/agl/ed25519  7.500s

Making key generation, signing, and verification a rough average of one third faster, one fifth faster, and one eighth faster respectively. Of course, this is just my machine, and these results—nowhere near rigorous—should be taken with a handful of salt.

Additionally, if you're on the Rust nightly channel, be sure to build with cargo build --features="nightly", which uses Rust's experimental support for the u128 type in curve25519-dalek to speed up field arithmetic by roughly a factor of two. The benchmarks using nightly (on the same machine as above) are:

∃!isisⒶwintermute:(develop *$)~/code/rust/ed25519 ∴ cargo bench --features="bench nightly"
    Finished release [optimized] target(s) in 0.0 secs
     Running target/release/deps/ed25519_dalek-9d7f8674ae11ac39

running 6 tests
test ed25519::test::golden ... ignored
test ed25519::test::sign_verify ... ignored
test ed25519::test::unmarshal_marshal ... ignored
test ed25519::bench::key_generation ... bench:      31,160 ns/iter (+/- 8,597)
test ed25519::bench::sign           ... bench:      40,565 ns/iter (+/- 4,758)
test ed25519::bench::verify         ... bench:     106,146 ns/iter (+/- 2,796)

test result: ok. 0 passed; 0 failed; 3 ignored; 3 measured

Translating to a rough cycle count: we multiply by a factor of 2.6 to convert nanoseconds to cycles per second on a 2.6 GHz CPU, that's 275979 cycles for verification and 105469 for signing, which is competitive with the optimised assembly version included in the SUPERCOP benchmarking suite (albeit their numbers are for the older Nehalem microarchitecture).

Additionally, thanks to Rust, this implementation has both type and memory safety. It's also easily readable by a much larger set of people than those who can read qhasm, making it more readily and more easily auditable. We're of the opinion that, ultimately, these features—combined with speed—are more valuable than simply cycle counts alone.

Warnings

ed25519-dalek and our elliptic curve library (which this code uses) have received one formal cryptographic and security review. Neither have yet received what we would consider sufficient peer review by other qualified cryptographers to be considered in any way, shape, or form, safe.

USE AT YOUR OWN RISK.

A Note on Signature Malleability

The signatures produced by this library are malleable, as discussed in the original paper:

We could eliminate the malleability property by multiplying by the curve cofactor, however, this would cause our implementation to not match the behaviour of every other implementation in existence. As of this writing, RFC 8032, "Edwards-Curve Digital Signature Algorithm (EdDSA)," advises that the stronger check should be done. While we agree that the stronger check should be done, it is our opinion that one shouldn't get to change the definition of "ed25519 verification" a decade after the fact, breaking compatibility with every other implementation.

In short, if malleable signatures are bad for your protocol, don't use them. Consider using a curve25519-based Verifiable Random Function (VRF), such as Trevor Perrin's VXEdDSA, instead. We plan to eventually support VXEdDSA in curve25519-dalek.

Installation

To install, add the following to your project's Cargo.toml:

[dependencies.ed25519-dalek]
version = "^0.6"

Then, in your library or executable source, add:

extern crate ed25519_dalek

To cause your application to build ed25519-dalek with the nightly feature enabled by default, instead do:

[dependencies.ed25519-dalek]
version = "^0.6"
features = ["nightly"]

To cause your application to instead build with the nightly feature enabled when someone builds with cargo build --features="nightly" add the following to the Cargo.toml:

[features]
nightly = ["ed25519-dalek/nightly"]

Using the nightly feature will nearly double the latency of signing and verification.

To enable serde support, build ed25519-dalek with:

[dependencies.ed25519-dalek]
version = "^0.6"
features = ["serde"]

TODO

We can probably make this go even faster if we implement SHA512, rather than using the rust-crypto implementation whose API requires that we allocate memory and memzero it before mutating to store the digest.
Incorporate ed25519-dalek into Brian Smith's crypto-bench.

ed25519-dalek 0.6.2