a poor implementation w/ discarding the 5 most significant bits... will fix after I implement in JS first.

blame-bip-poc.go

package main

import (
	"bytes"
	"crypto/md5"
	"fmt"
	"io/ioutil"
	"log"
	"os"
	"strings"
)

const (
	salt     string = "abc"
	myDomain string = "mydomain.example"

	bipFile string = "bip39.txt"
)

func main() {
	if len(os.Args) != 2 {
		log.Fatal("you must provide exactly one domain as argument")
	}
	domain := os.Args[1]
	sum := md5.Sum([]byte(domain + "+" + salt))
	var nums []int
	// read two bytes (16 bits)
	for i := 0; i < len(sum)-1; i++ {
		x := int(sum[i])<<8 | int(sum[i+1])
		// ... and save the least significant 11 bits
		x &= 0x7ff
		nums = append(nums, x)
	}
	bipnums := nums[0:3]
	// for each number, map to wordlist numbers
	var addr string
	for _, i := range bipnums {
		word, err := wordFromIndex(bipFile, i)
		if err != nil {
			log.Fatal(err)
		}
		if len(addr) == 0 {
			addr = word
		} else {
			addr = strings.Join([]string{addr, word}, ".")
		}
	}
	log.Printf("%s@%s\n", addr, myDomain)
}

func wordFromIndex(file string, index int) (string, error) {
	dat, err := ioutil.ReadFile(file)
	if err != nil {
		return "", err
	}
	words := bytes.Split(dat, []byte("\n"))
	if index > len(words) {
		return "", fmt.Errorf("index out of range")
	}
	return string(words[index]), nil
}