path: root/ethcrypto/mnemonic.go

package ethcrypto

import (
    "fmt"
    "io/ioutil"
    "os"
    "path"
    "path/filepath"
    "strconv"
    "strings"
)

func InitWords(wordsPath string) {
    filename := path.Join(wordsPath, "mnemonic.words.lst")
    if _, err := os.Stat(filename); os.IsNotExist(err) {
        fmt.Printf("reading mnemonic word list file from supplied path not found. Looked in %s. Trying next option.\n", filename)

        dir := path.Join(os.Getenv("GOPATH"), "src", "github.com", "ethereum", "eth-go", "ethcrypto")
        filename = path.Join(dir, "mnemonic.words.lst")
        if _, err := os.Stat(filename); os.IsNotExist(err) {
            fmt.Printf("reading mnemonic word list file 'mnemonic.words.lst' from source folder failed: %s.\n", filename)
            dir, err := filepath.Abs(filepath.Dir(os.Args[0]))
            if err != nil {
                panic(fmt.Errorf("problem getting current folder: ", err))
            }
            filename = path.Join(dir, "mnemonic.words.lst")
        }
    }

    content, err := ioutil.ReadFile(filename)
    if err != nil {
        panic(fmt.Errorf("All options for finding the mnemonic word list file 'mnemonic.words.lst' failed: ", err))
    }
    words = strings.Split(string(content), "\n")
}

var words []string

// TODO: See if we can refactor this into a shared util lib if we need it multiple times
func IndexOf(slice []string, value string) int64 {
    for p, v := range slice {
        if v == value {
            return int64(p)
        }
    }
    return -1
}

func MnemonicEncode(message string) []string {
    var out []string
    n := int64(len(words))

    for i := 0; i < len(message); i += (len(message) / 8) {
        x := message[i : i+8]
        bit, _ := strconv.ParseInt(x, 16, 64)
        w1 := (bit % n)
        w2 := ((bit / n) + w1) % n
        w3 := ((bit / n / n) + w2) % n
        out = append(out, words[w1], words[w2], words[w3])
    }
    return out
}

func MnemonicDecode(wordsar []string) string {
    var out string
    n := int64(len(words))

    for i := 0; i < len(wordsar); i += 3 {
        word1 := wordsar[i]
        word2 := wordsar[i+1]
        word3 := wordsar[i+2]
        w1 := IndexOf(words, word1)
        w2 := IndexOf(words, word2)
        w3 := IndexOf(words, word3)

        y := (w2 - w1) % n
        z := (w3 - w2) % n

        // Golang handles modulo with negative numbers different then most languages
        // The modulo can be negative, we don't want that.
        if z < 0 {
            z += n
        }
        if y < 0 {
            y += n
        }
        x := w1 + n*(y) + n*n*(z)
        out += fmt.Sprintf("%08x", x)
    }
    return out
}