move ethutil/mnemonic to ethcrypto - electrum word list now sourced from file

1 files changed, 76 insertions, 0 deletions

diff --git a/ethcrypto/mnemonic.go b/ethcrypto/mnemonic.go
new file mode 100644
index 000000000..6134f85f7
--- /dev/null
+++ b/ethcrypto/mnemonic.go
@@ -0,0 +1,76 @@
+package ethcrypto
+
+import (
+	"fmt"
+	"io/ioutil"
+	"path"
+	"runtime"
+	"strconv"
+	"strings"
+)
+
+func InitWords() []string {
+	_, thisfile, _, _ := runtime.Caller(1)
+	filename := path.Join(path.Dir(thisfile), "mnemonic.words.lst")
+	content, err := ioutil.ReadFile(filename)
+	if err != nil {
+		panic(fmt.Errorf("reading mnemonic word list file 'mnemonic.words.lst' failed: ", err))
+	}
+	return strings.Split(string(content), "\n")
+}
+
+var words = InitWords()
+
+// 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
+}