From fd9da72536b73351bbcdc1e9dbbbb8c0e4bfb21b Mon Sep 17 00:00:00 2001
From: obscuren <geffobscura@gmail.com>
Date: Fri, 31 Oct 2014 12:37:43 +0100
Subject: ethcrypto => crypto

---
 crypto/mnemonic.go | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)
 create mode 100644 crypto/mnemonic.go

(limited to 'crypto/mnemonic.go')

diff --git a/crypto/mnemonic.go b/crypto/mnemonic.go
new file mode 100644
index 000000000..0d690f245
--- /dev/null
+++ b/crypto/mnemonic.go
@@ -0,0 +1,60 @@
+package crypto
+
+import (
+	"fmt"
+	"strconv"
+)
+
+// 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(MnemonicWords))
+
+	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, MnemonicWords[w1], MnemonicWords[w2], MnemonicWords[w3])
+	}
+	return out
+}
+
+func MnemonicDecode(wordsar []string) string {
+	var out string
+	n := int64(len(MnemonicWords))
+
+	for i := 0; i < len(wordsar); i += 3 {
+		word1 := wordsar[i]
+		word2 := wordsar[i+1]
+		word3 := wordsar[i+2]
+		w1 := IndexOf(MnemonicWords, word1)
+		w2 := IndexOf(MnemonicWords, word2)
+		w3 := IndexOf(MnemonicWords, 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
+}
-- 
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