Example of generating Tor onions using the new ED25519-v3 format

tor-ed25519.go

// Example of generating Tor onion using the new ED25519-v3 format

package main

import (
	"crypto/rand"
	"crypto/sha512"
	"encoding/base32"
	"encoding/base64"
	"fmt"
	"golang.org/x/crypto/ed25519"
	"golang.org/x/crypto/sha3"
	"log"
	"strings"
)

// Hidden service version
const version = byte(0x03)

// Salt used to create checkdigits
const salt = ".onion checksum"

func main() {
	pub, pri, err := ed25519.GenerateKey(rand.Reader)
	if err != nil {
		log.Fatal(err)
	}
	fmt.Println("Address:", getServiceID(pub)+".onion")
	fmt.Println("Private Key:", expandKey(pri))
}

// Expand ed25519.PrivateKey to (a || RH) form, return base64
func expandKey(pri ed25519.PrivateKey) string {
	h := sha512.Sum512(pri[:32])
	// Set bits so that h[:32] is private scalar "a"
	h[0] &= 248
	h[31] &= 127
	h[31] |= 64
	// Since h[32:] is RH, h is now (a || RH)
	return base64.StdEncoding.EncodeToString(h[:])
}

func getCheckdigits(pub ed25519.PublicKey) []byte {
	// Calculate checksum sha3(".onion checksum" || publicKey || version)
	checkstr := []byte(salt)
	checkstr = append(checkstr, pub...)
	checkstr = append(checkstr, version)
	checksum := sha3.Sum256(checkstr)
	return checksum[:2]
}

func getServiceID(pub ed25519.PublicKey) string {
	// Construct onion address base32(publicKey || checkdigits || version)
	checkdigits := getCheckdigits(pub)
	combined := pub[:]
	combined = append(combined, checkdigits...)
	combined = append(combined, version)
	serviceID := base32.StdEncoding.EncodeToString(combined)
	return strings.ToLower(serviceID)
}

Does this accept existing public v3 .onion address as $ARGV[1] or something, or do I need to hack it? apologies, haven't written much Go lately.

@ageis it's just generates an onion domain and it's private key. But the public key is not stored.

You can try my version vanity onion generator https://github.com/stokito/oniongen-go/tree/optimization (note the branch is optimization )