ed25519

ed25519-recovery

Package ed25519-recovery implements a modified Ed25519 signature algorithm that allows for public key recovery.

It is based on the Ed25519 signature scheme implemented by the Go 1.20.1 standard library.

ed25519-recovery and achieves public key recovery by removal of the public key from the pre-image of the SHA512 digest in the calculation of S.

Motivation

Key recovery allows to save on data that needs to be transferred with signed messages. Note: there's a computational cost for extracting the public key, so one should consider the trade-off between computations and data size.

Usage

import ed25519 "github.com/spacemeshos/ed25519-recovery"

func example() {
    // Generate a key pair.
    privateKey, publicKey, err := ed25519.GenerateKey(rand.Reader)
    if err != nil {
        panic(err)
    }

    // Sign a message.
    message := []byte("Hello, world!")
    signature := ed25519.Sign(privateKey, message)

    // Extract the public key from the signature...
    extractedPublicKey := ed25519.ExtractPublicKey(message, signature)

    // ... or verify the signature using the public key.
    if !ed25519.Verify(publicKey, message, signature) {
        panic("invalid signature")
    }
}

Benchmarks

The benchmarks can be executed with go test -bench ..

Benchmark_Go_Sign-6                      52352     22548 ns/op       0 B/op       0 allocs/op
Benchmark_Go_Verify-6                    25263     47206 ns/op       0 B/op       0 allocs/op
Benchmark_Spacemesh_Sign-6               52512     22942 ns/op       0 B/op       0 allocs/op
Benchmark_Spacemesh_Verify-6             25344     47545 ns/op       0 B/op       0 allocs/op
Benchmark_Spacemesh_KeyExtraction-6      16887     69857 ns/op       0 B/op       0 allocs/op

Testing

Some of the tests require python3 and the pip package pure25519 to be installed. These tests fuzz the implemented functions and compare the results to the python reference implementation in internal/pure25519.

To run the tests, execute go test ./... -v. There are also fuzzing tests that can be run with

go test -fuzz=Fuzz_ExtractPublicKey -fuzztime=20s
go test -fuzz=Fuzz_Sign -fuzztime=20s
go test -fuzz=Fuzz_Derive -fuzztime=20s