quick and dirty go impl of tor hsv3 onion address generation

v3hsaddr.go

package main

import (
	"crypto/ed25519"
	"encoding/base32"
	"encoding/hex"
	"fmt"
	"strings"

	"golang.org/x/crypto/sha3"
)

func main() {
	var pubkey string = "d75a980182b10ab7d54bfed3c964073a0ee172f3daa62325af021a68f707511a"
	var version byte = 3

	checksum := v3checksum(decodePubkey(pubkey), version)

	address := append(decodePubkey(pubkey), checksum...)
	address = append(address, version)
	onion := strings.ToLower(base32.StdEncoding.EncodeToString(address))
	fmt.Println(onion)
}

func decodePubkey(encoded string) (decoded []byte) {
	decoded, err := hex.DecodeString(encoded)
	if err != nil {
		panic(err)
	}
	if len(decoded) != ed25519.PublicKeySize {
		panic("invalid key data length")
	}
	return decoded
}

func v3checksum(pubkey []byte, version byte) (checksum []byte) {
	prefix := []byte(".onion checksum")
	data := append(prefix, pubkey...)
	data = append(data, version)
	shasum := sha3.Sum256(data)
	checksum = shasum[:][:2]
	return checksum
}