ed255519 -> curve25519

test.go

package main

import (
	"crypto/rand"
	"fmt"

	"github.com/agl/ed25519"
	"github.com/agl/ed25519/extra25519"
	"github.com/monetas/gotary/util/enc"
)

func newk() (*[32]byte, *[32]byte) {
	edpk, edsk, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		panic(err)
	}
	cpk := new([32]byte)
	if !extra25519.PublicKeyToCurve25519(cpk, edpk) {
		panic("nope")
	}
	csk := new([32]byte)
	extra25519.PrivateKeyToCurve25519(csk, edsk)
	return cpk, csk
}

func main() {
	ns, err := enc.NewNonceStream()
	if err != nil {
		panic(err)
	}
	for i := 0; i < 10000; i++ {
		pk, sk := newk()
		pk2, sk2 := newk()
		cipher, err := enc.Encrypt([]byte("LOL"), pk2, sk, ns)
		if err != nil {
			panic(err)
		}
		decrypted, err := enc.Decrypt(cipher, pk, sk2)
		if err != nil {
			panic(err)
		}
		fmt.Println(string(decrypted))
	}
}

package main

import (
    "crypto/rand"
    "fmt"

    "golang.org/x/crypto/curve25519"
    "golang.org/x/crypto/nacl/box"

    "github.com/agl/ed25519/extra25519"
)

func main() {
    n := 1000
    failed := 0
    repr := new([32]byte)
    for i := 0; i < n; i++ {
        pk, sk, err := box.GenerateKey(rand.Reader)
        if err != nil {
            panic(err)
        }
        pk2 := new([32]byte)
        curve25519.ScalarBaseMult(pk2, sk)
        if *pk != *pk2 {
            panic("nope")
        }

        if !extra25519.ScalarBaseMult(pk2, repr, sk) {
            failed++
        }
    }
    fmt.Println("failed ", 100*float32(failed)/float32(n), "%")
}

Output: failed 50.3 %